Merge branch 'feature/socket-rework' into master

CHANGELOG.md

@@ -6,6 +6,45 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic
 Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+- The way communication works in yabridge has been completely redesigned to be
+  asynchronous and to use additional threads as necessary. This was needed to
+  allow yabridge to handle nested and mutually recursive function calls as well
+  as several other edge cases. What this boils down to is that yabridge became
+  even faster, more responsive, and can now handle a few edge case scenarios
+  that would previously require workarounds. This means that yabridge no longer
+  requires the `hack_reaper_update_display` workaround for _REAPER_ and
+  _Renoise_, that the loading issues in Bitwig Studio 3.3 beta 1 have also been
+  resolved, and that certain plugins like Kontakt no longer interrupt playback
+  in Bitwig while their editor is opening. I have been testing this extensively
+  to make sure that the change does not introduce any regressions, but please
+  let me know if this does break anything for you.
+
+  TODO: Expand on this  
+  TODO: Remove known issue about opening Kontakt and certain other plugins
+  causing playback to stall, since this is no longer the case
+
+### Changed
+
+- As part of the communication rework the way the Wine process handles threading
+  has also been completely reworked.
+
+### Removed
+
+- The `hack_reaper_update_display` option is now obsolete and has been removed.
+
+  TODO: Remove all mentions of `hack_reaper_update_display` from the readme.
+
+### Fixed
+
+- Fixed a very long standing issue when using plugins groups where unloading a
+  plugin could cause a crash. In practice this was only reproducible during the
+  plugin scanning process when hosting a very large number of plugins in a
+  single group.
+
 ## [1.7.1] - 2020-10-23
 
 ### Fixed

README.md

@@ -38,10 +38,10 @@ compatibility while also staying easy to debug and maintain.
 Yabridge has been tested under the following VST hosts using Wine Staging 5.9:
 
 - Bitwig Studio 3.2
-- Carla 2.1
-- Ardour 6.2
+- Carla 2.2
+- Ardour 6.3
 - Mixbus 6.0.702
-- REAPER 6.09[\*](#runtime-dependencies-and-known-issues)
+- REAPER 6.15[\*](#runtime-dependencies-and-known-issues)
 - Renoise 3.2.1[\*](#runtime-dependencies-and-known-issues)
 
 Please let me know if there are any issues with other VST hosts.
@@ -499,6 +499,7 @@ the following dependencies:
 The following dependencies are included in the repository as a Meson wrap:
 
 - bitsery
+- function2
 - tomlplusplus
 
 The project can then be compiled as follows:

docs/architecture.md

@@ -1,5 +1,7 @@
 # Architecture
 
+<!-- TODO: Mention the new special socket approach for `dispatch()` and `audioMaster()-->
+
 The project consists of two components: a Linux native VST plugin
 (`libyabridge.so`) and a VST host that runs under Wine
 (`yabridge-host.exe`/`yabridge-host.exe.so`, and
@@ -38,22 +40,24 @@ as the _Windows VST plugin_. The whole process works as follows:
    - The Wine prefix the plugin is located in. If the `WINEPREFIX` environment
      variable is specified, then that will be used instead.
 
-3. The plugin then sets up a Unix domain socket endpoint to communicate with the
-   Wine VST host somewhere in a temporary directory and starts listening on it.
-   I chose to communicate over Unix domain sockets rather than using shared
-   memory directly because this way you get low latency communication with
-   without any busy waits or manual synchronisation for free. The added benefit
-   is that it also makes it possible to send arbitrarily large chunks of data
-   without having to split it up first. This is useful for transmitting audio
-   and preset data which may have any arbitrary size.
+3. The plugin then sets up several Unix domain socket endpoints to communicate
+   with the Wine VST host somewhere in a temporary directory and starts
+   listening on them. We'll use multiple sockets so we can easily handle
+   multiple data streams from different threads using blocking synchronous
+   operations. This greatly simplifies the way communication works without
+   compromising on latency. The different sockets will be described below. We
+   communicate over Unix domain sockets rather than using shared memory directly
+   because this way we get low latency communication without any manual
+   synchronisation for free, while being able to send messages of arbitrary
+   length without having to split them up first. This is useful for transmitting
+   audio and preset data which can be any arbitrary size.
 4. The plugin launches the Wine VST host in the detected wine prefix, passing
-   the name of the `.dll` file it should be loading and the path to the Unix
-   domain socket that was just created as its arguments.
-5. Communication gets set up using multiple sockets over the end point created
-   previously. This allows us to easily handle multiple data streams from
-   different threads using blocking read operations for synchronization. Doing
-   this greatly simplifies the way communication works without compromising on
-   latency. The following types of events each get their own socket:
+   the name of the `.dll` file it should be loading and the base directory for
+   the Unix domain sockets that are going to be communciated over as its
+   arguments.
+5. The Wine VST host connects to the sockets and communication between the
+   plugin and the Wine VST host gets set up. The following types of events each
+   get their own socket:
 
    - Calls from the native VST host to the plugin's `dispatcher()` function.
      These get forwarded to the Windows VST plugin through the Wine VST host.
@@ -103,25 +107,27 @@ as the _Windows VST plugin_. The whole process works as follows:
    are located in `src/common/communication.h`. The actual binary serialization
    is handled using [bitsery](https://github.com/fraillt/bitsery).
 
-   Actually sending and receiving the events happens in the `send_event()` and
-   `receive_event()` functions. When calling either `dispatch()` or
-   `audioMaster()`, the caller will oftentimes either pass along some kind of
-   data structure through the void pointer function argument, or they expect the
-   function's return value to be a pointer to some kind of struct provided by
-   the plugin or host. The behaviour for reading from and writing into these
-   void pointers and returning pointers to objects when needed is encapsulated
-   in the `DispatchDataConverter` and `HostCallbackDataCovnerter` classes for
-   the `dispatcher()` and `audioMaster()` functions respectively. For operations
-   involving the plugin editor there is also some extra glue in
-   `Vst2Bridge::dispatch_wrapper`. On the receiving end of the function calls,
-   the `passthrough_event()` function which calls the callback functions and
-   handles the marshalling between our data types created by the
-   `*DataConverter` classes and the VST API's different pointer types. This
-   behaviour is separated from `receive_event()` so we can handle MIDI events
-   separately. This is needed because a select few plugins only store pointers
-   to the received events rather than copies of the objects. Because of this,
-   the received event data must live at least until the next audio buffer gets
-   processed so it needs to be stored temporarily.
+   TODO: Rewrite this after the socket changes are done
+
+   Actually sending and receiving the events happens in the
+   `EventHandler::send()` and `EventHandler::receive()` functions. When calling
+   either `dispatch()` or `audioMaster()`, the caller will oftentimes either
+   pass along some kind of data structure through the void pointer function
+   argument, or they expect the function's return value to be a pointer to some
+   kind of struct provided by the plugin or host. The behaviour for reading from
+   and writing into these void pointers and returning pointers to objects when
+   needed is encapsulated in the `DispatchDataConverter` and
+   `HostCallbackDataCovnerter` classes for the `dispatcher()` and
+   `audioMaster()` functions respectively. For operations involving the plugin
+   editor there is also some extra glue in `Vst2Bridge::dispatch_wrapper`. On
+   the receiving end of the function calls, the `passthrough_event()` function
+   which calls the callback functions and handles the marshalling between our
+   data types created by the `*DataConverter` classes and the VST API's
+   different pointer types. This behaviour is separated from `receive_event()`
+   so we can handle MIDI events separately. This is needed because a select few
+   plugins only store pointers to the received events rather than copies of the
+   objects. Because of this, the received event data must live at least until
+   the next audio buffer gets processed so it needs to be stored temporarily.
 
 6. The Wine VST host loads the Windows VST plugin and starts forwarding messages
    over the sockets described above.

meson.build

@@ -73,6 +73,7 @@ boost_filesystem_dep = dependency(
   static : with_static_boost
 )
 bitsery_dep = subproject('bitsery').get_variable('bitsery_dep')
+function2_dep = subproject('function2').get_variable('function2_dep')
 threads_dep = dependency('threads')
 tomlplusplus_dep = subproject('tomlplusplus', version : '2.1.0').get_variable('tomlplusplus_dep')
 # The built in threads dependency does not know how to handle winegcc
@@ -92,6 +93,7 @@ shared_library(
     'src/common/configuration.cpp',
     'src/common/logging.cpp',
     'src/common/serialization.cpp',
+    'src/common/communication.cpp',
     'src/common/utils.cpp',
     'src/plugin/host-process.cpp',
     'src/plugin/plugin.cpp',
@@ -116,6 +118,7 @@ host_sources = [
   'src/common/configuration.cpp',
   'src/common/logging.cpp',
   'src/common/serialization.cpp',
+  'src/common/communication.cpp',
   'src/common/utils.cpp',
   'src/wine-host/bridges/vst2.cpp',
   'src/wine-host/editor.cpp',
@@ -139,6 +142,7 @@ executable(
     boost_dep,
     boost_filesystem_dep,
     bitsery_dep,
+    function2_dep,
     tomlplusplus_dep,
     wine_threads_dep,
     xcb_dep
@@ -156,6 +160,7 @@ executable(
     boost_dep,
     boost_filesystem_dep,
     bitsery_dep,
+    function2_dep,
     tomlplusplus_dep,
     wine_threads_dep,
     xcb_dep
@@ -201,6 +206,7 @@ if with_bitbridge
       boost_dep,
       boost_filesystem_dep,
       bitsery_dep,
+      function2_dep,
       tomlplusplus_dep,
       wine_threads_dep,
       xcb_dep
@@ -225,6 +231,7 @@ if with_bitbridge
       boost_dep,
       boost_filesystem_dep,
       bitsery_dep,
+      function2_dep,
       tomlplusplus_dep,
       wine_threads_dep,
       xcb_dep

src/common/communication.cpp

@@ -0,0 +1,107 @@
+// yabridge: a Wine VST bridge
+// Copyright (C) 2020  Robbert van der Helm
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+#include "communication.h"
+
+#include <random>
+
+#include "utils.h"
+
+namespace fs = boost::filesystem;
+
+/**
+ * Used for generating random identifiers.
+ */
+constexpr char alphanumeric_characters[] =
+    "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+
+EventPayload DefaultDataConverter::read(const int /*opcode*/,
+                                        const int /*index*/,
+                                        const intptr_t /*value*/,
+                                        const void* data) const {
+    if (!data) {
+        return nullptr;
+    }
+
+    // This is a simple fallback that will work in almost every case.
+    // Because some plugins don't zero out their string buffers when sending
+    // host callbacks, we will explicitely list all callbacks that expect a
+    // string in `DispatchDataConverter` adn `HostCallbackDataConverter`.
+    const char* c_string = static_cast<const char*>(data);
+    if (c_string[0] != 0) {
+        return std::string(c_string);
+    } else {
+        return WantsString{};
+    }
+}
+
+std::optional<EventPayload> DefaultDataConverter::read_value(
+    const int /*opcode*/,
+    const intptr_t /*value*/) const {
+    return std::nullopt;
+}
+
+void DefaultDataConverter::write(const int /*opcode*/,
+                                 void* data,
+                                 const EventResult& response) const {
+    // The default behavior is to handle this as a null terminated C-style
+    // string
+    std::visit(overload{[&](const auto&) {},
+                        [&](const std::string& s) {
+                            char* output = static_cast<char*>(data);
+
+                            // We use std::string for easy transport but in
+                            // practice we're always writing null terminated
+                            // C-style strings
+                            std::copy(s.begin(), s.end(), output);
+                            output[s.size()] = 0;
+                        }},
+               response.payload);
+}
+
+void DefaultDataConverter::write_value(const int /*opcode*/,
+                                       intptr_t /*value*/,
+                                       const EventResult& /*response*/) const {}
+
+intptr_t DefaultDataConverter::return_value(const int /*opcode*/,
+                                            const intptr_t original) const {
+    return original;
+}
+
+boost::filesystem::path generate_endpoint_base(const std::string& plugin_name) {
+    fs::path temp_directory = get_temporary_directory();
+
+    std::random_device random_device;
+    std::mt19937 rng(random_device());
+    fs::path candidate_endpoint;
+    do {
+        std::string random_id;
+        std::sample(
+            alphanumeric_characters,
+            alphanumeric_characters + strlen(alphanumeric_characters) - 1,
+            std::back_inserter(random_id), 8, rng);
+
+        // We'll get rid of the file descriptors immediately after accepting the
+        // sockets, so putting them inside of a subdirectory would only leave
+        // behind an empty directory
+        std::ostringstream socket_name;
+        socket_name << "yabridge-" << plugin_name << "-" << random_id;
+
+        candidate_endpoint = temp_directory / socket_name.str();
+    } while (fs::exists(candidate_endpoint));
+
+    return candidate_endpoint;
+}

src/common/communication.h

@@ -16,15 +16,22 @@
 
 #pragma once
 
+#include <atomic>
+#include <iostream>
+
 #include <bitsery/adapter/buffer.h>
 #include <bitsery/bitsery.h>
 
 #ifdef __WINE__
 #include "../wine-host/boost-fix.h"
 #endif
+#include <boost/asio/io_context.hpp>
 #include <boost/asio/local/stream_protocol.hpp>
 #include <boost/asio/read.hpp>
 #include <boost/asio/write.hpp>
+#include <boost/filesystem.hpp>
+
+#include "logging.h"
 
 template <typename B>
 using OutputAdapter = bitsery::OutputBufferAdapter<B>;
@@ -108,9 +115,847 @@ inline T read_object(Socket& socket,
             {buffer.begin(), size}, object);
 
     if (BOOST_UNLIKELY(!success)) {
-        throw std::runtime_error("Deserialization failure in call:" +
+        throw std::runtime_error("Deserialization failure in call: " +
                                  std::string(__PRETTY_FUNCTION__));
     }
 
     return object;
 }
+
+/**
+ * Encodes the base behavior for reading from and writing to the `data` argument
+ * for event dispatch functions. This provides base functionality for these
+ * kinds of events. The `dispatch()` function will require some more specific
+ * structs.
+ */
+class DefaultDataConverter {
+   public:
+    virtual ~DefaultDataConverter(){};
+
+    /**
+     * Read data from the `data` void pointer into a an `EventPayload` value
+     * that can be serialized and conveys the meaning of the event.
+     */
+    virtual EventPayload read(const int opcode,
+                              const int index,
+                              const intptr_t value,
+                              const void* data) const;
+
+    /**
+     * Read data from the `value` pointer into a an `EventPayload` value that
+     * can be serialized and conveys the meaning of the event. This is only used
+     * for the `effSetSpeakerArrangement` and `effGetSpeakerArrangement` events.
+     */
+    virtual std::optional<EventPayload> read_value(const int opcode,
+                                                   const intptr_t value) const;
+
+    /**
+     * Write the reponse back to the `data` pointer.
+     */
+    virtual void write(const int opcode,
+                       void* data,
+                       const EventResult& response) const;
+
+    /**
+     * Write the reponse back to the `value` pointer. This is only used during
+     * the `effGetSpeakerArrangement` event.
+     */
+    virtual void write_value(const int opcode,
+                             intptr_t value,
+                             const EventResult& response) const;
+
+    /**
+     * This function can override a callback's return value based on the opcode.
+     * This is used in one place to return a pointer to a `VstTime` object
+     * that's contantly being updated.
+     *
+     * @param opcode The opcode for the current event.
+     * @param original The original return value as returned by the callback
+     *   function.
+     */
+    virtual intptr_t return_value(const int opcode,
+                                  const intptr_t original) const;
+};
+
+/**
+ * So, this is a bit of a mess. The TL;DR is that we want to use a single long
+ * living socket connection for `dispatch()` and another one for `audioMaster()`
+ * for performance reasons, but when the socket is already being written to we
+ * create new connections on demand.
+ *
+ * For most of our sockets we can just send out our messages on the writing
+ * side, and do a simple blocking loop on the reading side. The `dispatch()` and
+ * `audioMaster()` calls are different. Not only do they have they come with
+ * complex payload values, they can also be called simultaneously from multiple
+ * threads, and `audioMaster()` and `dispatch()` calls can even be mutually
+ * recursive. Luckily this does not happen very often, but it does mean that our
+ * simple 'one-socket-per-function' model doesn't work anymore. Because setting
+ * up new sockets is quite expensive and this is seldom needed, this works
+ * slightly differently:
+ *
+ * - We'll keep a single long lived socket connection. This works the exact same
+ *   way as every other socket defined in the `Sockets` class.
+ * - Aside from that the listening side will have a second thread asynchronously
+ *   listening for new connections on the socket endpoint.
+ *
+ * The `EventHandler::send()` is used to send events. If the socket is currently
+ * being written to, we'll first create a new socket connection as described
+ * above. Similarly, the `EventHandler::receive()` method first sets up
+ * asynchronous listeners for the socket endpoint, and then block and handle
+ * events until the main socket is closed.
+ *
+ * @tparam Thread The thread implementation to use. On the Linux side this
+ *   should be `std::jthread` and on the Wine side this should be `Win32Thread`.
+ */
+template <typename Thread>
+class EventHandler {
+   public:
+    /**
+     * Sets up a single main socket for this type of events. The sockets won't
+     * be active until `connect()` gets called.
+     *
+     * @param io_context The IO context the main socket should be bound to. A
+     *   new IO context will be created for accepting the additional incoming
+     *   connections.
+     * @param endpoint The socket endpoint used for this event handler.
+     * @param listen If `true`, start listening on the sockets. Incoming
+     *   connections will be accepted when `connect()` gets called. This should
+     *   be set to `true` on the plugin side, and `false` on the Wine host side.
+     *
+     * @see Sockets::connect
+     */
+    EventHandler(boost::asio::io_context& io_context,
+                 boost::asio::local::stream_protocol::endpoint endpoint,
+                 bool listen)
+        : io_context(io_context), endpoint(endpoint), socket(io_context) {
+        if (listen) {
+            boost::filesystem::create_directories(
+                boost::filesystem::path(endpoint.path()).parent_path());
+            acceptor.emplace(io_context, endpoint);
+        }
+    }
+
+    /**
+     * Depending on the value of the `listen` argument passed to the
+     * constructor, either accept connections made to the sockets on the Linux
+     * side or connect to the sockets on the Wine side
+     */
+    void connect() {
+        if (acceptor) {
+            acceptor->accept(socket);
+
+            // As mentioned in `acceptor's` docstring, this acceptor will be
+            // recreated in `receive()` on another context, and potentially on
+            // the other side of the connection in the case of
+            // `vst_host_callback`
+            acceptor.reset();
+            boost::filesystem::remove(endpoint.path());
+        } else {
+            socket.connect(endpoint);
+        }
+    }
+
+    /**
+     * Close the socket. Both sides that are actively listening will be thrown a
+     * `boost::system_error` when this happens.
+     */
+    void close() {
+        // The shutdown can fail when the socket is already closed
+        boost::system::error_code err;
+        socket.shutdown(
+            boost::asio::local::stream_protocol::socket::shutdown_both, err);
+        socket.close();
+    }
+
+    /**
+     * Serialize and send an event over a socket. This is used for both the host
+     * -> plugin 'dispatch' events and the plugin -> host 'audioMaster' host
+     * callbacks since they follow the same format. See one of those functions
+     * for details on the parameters and return value of this function.
+     *
+     * As described above, if this function is currently being called from
+     * another thread, then this will create a new socket connection and send
+     * the event there instead.
+     *
+     * @param data_converter Some struct that knows how to read data from and
+     *   write data back to the `data` void pointer. For host callbacks this
+     *   parameter contains either a string or a null pointer while `dispatch()`
+     *   calls might contain opcode specific structs. See the documentation for
+     *   `EventPayload` for more information. The `DefaultDataConverter` defined
+     *   above handles the basic behavior that's sufficient for host callbacks.
+     * @param logging A pair containing a logger instance and whether or not
+     *   this is for sending `dispatch()` events or host callbacks. Optional
+     *   since it doesn't have to be done on both sides.
+     *
+     * @relates EventHandler::receive
+     * @relates passthrough_event
+     */
+    template <typename D>
+    intptr_t send(D& data_converter,
+                  std::optional<std::pair<Logger&, bool>> logging,
+                  int opcode,
+                  int index,
+                  intptr_t value,
+                  void* data,
+                  float option) {
+        // Encode the right payload types for this event. Check the
+        // documentation for `EventPayload` for more information. These types
+        // are converted to C-style data structures in `passthrough_event()` so
+        // they can be passed to a plugin or callback function.
+        const EventPayload payload =
+            data_converter.read(opcode, index, value, data);
+        const std::optional<EventPayload> value_payload =
+            data_converter.read_value(opcode, value);
+
+        if (logging) {
+            auto [logger, is_dispatch] = *logging;
+            logger.log_event(is_dispatch, opcode, index, value, payload, option,
+                             value_payload);
+        }
+
+        const Event event{.opcode = opcode,
+                          .index = index,
+                          .value = value,
+                          .option = option,
+                          .payload = payload,
+                          .value_payload = value_payload};
+
+        // A socket only handles a single request at a time as to prevent
+        // messages from arriving out of order. For throughput reasons we prefer
+        // to do most communication over a single main socket (`socket`), and
+        // we'll lock `write_mutex` while doing so. In the event that the mutex
+        // is already locked and thus the main socket is currently in use by
+        // another thread, then we'll spawn a new socket to handle the request.
+        EventResult response;
+        {
+            std::unique_lock lock(write_mutex, std::try_to_lock);
+            if (lock.owns_lock()) {
+                write_object(socket, event);
+                response = read_object<EventResult>(socket);
+            } else {
+                try {
+                    boost::asio::local::stream_protocol::socket
+                        secondary_socket(io_context);
+                    secondary_socket.connect(endpoint);
+
+                    write_object(secondary_socket, event);
+                    response = read_object<EventResult>(secondary_socket);
+                } catch (const boost::system::system_error&) {
+                    // So, what do we do when noone is listening on the endpoint
+                    // yet? This can happen with plugin groups when the Wine
+                    // host process does an `audioMaster()` call before the
+                    // plugin is listening. If that happens we'll fall back to a
+                    // synchronous request. This is not very pretty, so if
+                    // anyone can think of a better way to structure all of this
+                    // while still mainting a long living primary socket please
+                    // let me know.
+                    std::lock_guard lock(write_mutex);
+
+                    write_object(socket, event);
+                    response = read_object<EventResult>(socket);
+                }
+            }
+        }
+
+        if (logging) {
+            auto [logger, is_dispatch] = *logging;
+            logger.log_event_response(is_dispatch, opcode,
+                                      response.return_value, response.payload,
+                                      response.value_payload);
+        }
+
+        data_converter.write(opcode, data, response);
+        data_converter.write_value(opcode, value, response);
+
+        return data_converter.return_value(opcode, response.return_value);
+    }
+
+    /**
+     * Spawn a new thread to listen for extra connections to `endpoint`, and
+     * then a blocking loop that handles events from the primary `socket`.
+     *
+     * The specified function will be used to create an `EventResult` from an
+     * `Event`. This is almost always a wrapper around `passthrough_event()`,
+     * which converts the `EventPayload` into a format used by VST2, calls
+     * either `dispatch()` or `audioMaster()` depending on the socket, and then
+     * serializes the result back into an `EventResultPayload`.
+     *
+     * This function will also be used separately for receiving MIDI data, as
+     * some plugins will need pointers to received MIDI data to stay alive until
+     * the next audio buffer gets processed.
+     *
+     * @param logging A pair containing a logger instance and whether or not
+     *   this is for sending `dispatch()` events or host callbacks. Optional
+     *   since it doesn't have to be done on both sides.
+     * @param callback The function used to generate a response out of an event.
+     *   See the definition of `F` for more information.
+     *
+     * @tparam F A function type in the form of `EventResponse(Event, bool)`.
+     *   The boolean flag is `true` when this event was received on the main
+     *   socket, and `false` otherwise.
+     *
+     * @relates EventHandler::send
+     * @relates passthrough_event
+     */
+    template <typename F>
+    void receive(std::optional<std::pair<Logger&, bool>> logging, F callback) {
+        // As described above we'll handle incoming requests for `socket` on
+        // this thread. We'll also listen for incoming connections on `endpoint`
+        // on another thread. For any incoming connection we'll spawn a new
+        // thread to handle the request. When `socket` closes and this loop
+        // breaks, the listener and any still active threads will be cleaned up
+        // before this function exits.
+        boost::asio::io_context secondary_context{};
+
+        // The previous acceptor has already been shut down by
+        // `EventHandler::connect()`
+        acceptor.emplace(secondary_context, endpoint);
+
+        // This works the exact same was as `active_plugins` and
+        // `next_plugin_id` in `GroupBridge`
+        std::map<size_t, Thread> active_secondary_requests{};
+        std::atomic_size_t next_request_id{};
+        std::mutex active_secondary_requests_mutex{};
+        accept_requests(
+            *acceptor, logging,
+            [&](boost::asio::local::stream_protocol::socket secondary_socket) {
+                const size_t request_id = next_request_id.fetch_add(1);
+
+                // We have to make sure to keep moving these sockets into the
+                // threads that will handle them
+                std::lock_guard lock(active_secondary_requests_mutex);
+                active_secondary_requests[request_id] = Thread(
+                    [&, request_id](boost::asio::local::stream_protocol::socket
+                                        secondary_socket) {
+                        // TODO: Factor this out
+                        auto event = read_object<Event>(secondary_socket);
+                        if (logging) {
+                            auto [logger, is_dispatch] = *logging;
+                            logger.log_event(is_dispatch, event.opcode,
+                                             event.index, event.value,
+                                             event.payload, event.option,
+                                             event.value_payload);
+                        }
+
+                        EventResult response = callback(event, false);
+                        if (logging) {
+                            auto [logger, is_dispatch] = *logging;
+                            logger.log_event_response(is_dispatch, event.opcode,
+                                                      response.return_value,
+                                                      response.payload,
+                                                      response.value_payload);
+                        }
+
+                        write_object(secondary_socket, response);
+
+                        // When we have processed this request, we'll join the
+                        // thread again with the thread that's handling
+                        // `secondary_context`.
+                        boost::asio::post(secondary_context, [&, request_id]() {
+                            std::lock_guard lock(
+                                active_secondary_requests_mutex);
+
+                            // The join is implicit because we're using
+                            // std::jthread/Win32Thread
+                            active_secondary_requests.erase(request_id);
+                        });
+                    },
+                    std::move(secondary_socket));
+            });
+
+        Thread secondary_requests_handler([&]() { secondary_context.run(); });
+
+        while (true) {
+            try {
+                auto event = read_object<Event>(socket);
+                if (logging) {
+                    auto [logger, is_dispatch] = *logging;
+                    logger.log_event(is_dispatch, event.opcode, event.index,
+                                     event.value, event.payload, event.option,
+                                     event.value_payload);
+                }
+
+                EventResult response = callback(event, true);
+                if (logging) {
+                    auto [logger, is_dispatch] = *logging;
+                    logger.log_event_response(
+                        is_dispatch, event.opcode, response.return_value,
+                        response.payload, response.value_payload);
+                }
+
+                write_object(socket, response);
+            } catch (const boost::system::system_error&) {
+                // This happens when the sockets got closed because the plugin
+                // is being shut down
+                break;
+            }
+        }
+
+        // After the main socket gets terminated (during shutdown) we'll make
+        // sure all outstanding jobs have been processed and then drop all work
+        // from the IO context
+        std::lock_guard lock(active_secondary_requests_mutex);
+        secondary_context.stop();
+        acceptor.reset();
+    }
+
+   private:
+    /**
+     * Used in `receive()` to asynchronously listen for secondary socket
+     * connections. After `callback()` returns this function will continue to be
+     * called until the IO context gets stopped.
+     *
+     * @param acceptor The acceptor we will be listening on.
+     * @param logging A pair containing a logger instance and whether or not
+     *   this is for sending `dispatch()` events or host callbacks. Optional
+     *   since it doesn't have to be done on both sides.
+     * @param callback A function that handles the new socket connection.
+     *
+     * @tparam F A function in the form
+     *   `void(boost::asio::local::stream_protocol::socket)` to handle a new
+     *   incoming connection.
+     */
+    template <typename F>
+    void accept_requests(
+        boost::asio::local::stream_protocol::acceptor& acceptor,
+        std::optional<std::pair<Logger&, bool>> logging,
+        F callback) {
+        acceptor.async_accept(
+            [&, logging, callback](
+                const boost::system::error_code& error,
+                boost::asio::local::stream_protocol::socket secondary_socket) {
+                if (error.failed()) {
+                    // On the Wine side it's expected that the main socket
+                    // connection will be dropped during shutdown, so we can
+                    // silently ignore any related socket errors on the Wine
+                    // side
+                    if (logging) {
+                        auto [logger, is_dispatch] = *logging;
+                        logger.log("Failure while accepting connections: " +
+                                   error.message());
+                    }
+
+                    return;
+                }
+
+                callback(std::move(secondary_socket));
+
+                accept_requests(acceptor, logging, callback);
+            });
+    }
+
+    /**
+     * The main IO context. New sockets created during `send()` will be bound to
+     * this context. In `receive()` we'll create a new IO context since we want
+     * to do all listening there on a dedicated thread.
+     */
+    boost::asio::io_context& io_context;
+
+    boost::asio::local::stream_protocol::endpoint endpoint;
+    boost::asio::local::stream_protocol::socket socket;
+
+    /**
+     * This acceptor will be used once synchronously on the listening side
+     * during `Sockets::connect()`. When `EventHandler::receive()` is then
+     * called, we'll recreate the acceptor asynchronously listen for new
+     * incoming socket connections on `endpoint` using this same acceptor. This
+     * is important, because on the case of `vst_host_callback` the acceptor is
+     * first accepts an initial socket on the plugin side (like all sockets),
+     * but all additional incoming connections of course have to be listened for
+     * on the plugin side.
+     */
+    std::optional<boost::asio::local::stream_protocol::acceptor> acceptor;
+
+    /**
+     * A mutex that locks the main `socket`. If this is locked, then any new
+     * events will be sent over a new socket instead.
+     */
+    std::mutex write_mutex;
+};
+
+/**
+ * Manages all the sockets used for communicating between the plugin and the
+ * Wine host. Every plugin will get its own directory (the socket endpoint base
+ * directory), and all socket endpoints are created within this directory. This
+ * is usually `/run/user/<uid>/yabridge-<plugin_name>-<random_id>/`.
+ *
+ * On the plugin side this class should be initialized with `listen` set to
+ * `true` before launching the Wine VST host. This will start listening on the
+ * sockets, and the call to `connect()` will then accept any incoming
+ * connections.
+ *
+ * @tparam Thread The thread implementation to use. On the Linux side this
+ *   should be `std::jthread` and on the Wine side this should be `Win32Thread`.
+ */
+template <typename Thread>
+class Sockets {
+   public:
+    /**
+     * Sets up the sockets using the specified base directory. The sockets won't
+     * be active until `connect()` gets called.
+     *
+     * @param io_context The IO context the sockets should be bound to. Relevant
+     *   when doing asynchronous operations.
+     * @param endpoint_base_dir The base directory that will be used for the
+     *   Unix domain sockets.
+     * @param listen If `true`, start listening on the sockets. Incoming
+     *   connections will be accepted when `connect()` gets called. This should
+     *   be set to `true` on the plugin side, and `false` on the Wine host side.
+     *
+     * @see Sockets::connect
+     */
+    Sockets(boost::asio::io_context& io_context,
+            const boost::filesystem::path& endpoint_base_dir,
+            bool listen)
+        : base_dir(endpoint_base_dir),
+          host_vst_dispatch(io_context,
+                            (base_dir / "host_vst_dispatch.sock").string(),
+                            listen),
+          host_vst_dispatch_midi_events(
+              io_context,
+              (base_dir / "host_vst_dispatch_midi_events.sock").string(),
+              listen),
+          vst_host_callback(io_context,
+                            (base_dir / "vst_host_callback.sock").string(),
+                            listen),
+          host_vst_parameters(io_context),
+          host_vst_process_replacing(io_context),
+          host_vst_control(io_context),
+          host_vst_parameters_endpoint(
+              (base_dir / "host_vst_parameters.sock").string()),
+          host_vst_process_replacing_endpoint(
+              (base_dir / "host_vst_process_replacing.sock").string()),
+          host_vst_control_endpoint(
+              (base_dir / "host_vst_control.sock").string()) {
+        if (listen) {
+            boost::filesystem::create_directories(base_dir);
+
+            acceptors = Acceptors{
+                .host_vst_parameters{io_context, host_vst_parameters_endpoint},
+                .host_vst_process_replacing{
+                    io_context, host_vst_process_replacing_endpoint},
+                .host_vst_control{io_context, host_vst_control_endpoint},
+            };
+        }
+    }
+
+    /**
+     * Cleans up the directory containing the socket endpoints when yabridge
+     * shuts down if it still exists.
+     */
+    ~Sockets() {
+        // Only clean if we're the ones who have created these files, although
+        // it should not cause any harm to also do this on the Wine side
+        if (acceptors) {
+            try {
+                boost::filesystem::remove_all(base_dir);
+            } catch (const boost::filesystem::filesystem_error&) {
+                // There should not be any filesystem errors since only one side
+                // removes the files, but if we somehow can't delete the file
+                // then we can just silently ignore this
+            }
+        }
+
+        // Manually close all sockets so we break out of any blocking operations
+        // that may still be active
+        host_vst_dispatch.close();
+        host_vst_dispatch_midi_events.close();
+        vst_host_callback.close();
+
+        // These shutdowns can fail when the socket has already been closed, but
+        // that's not an issue in our case
+        constexpr auto shutdown_type =
+            boost::asio::local::stream_protocol::socket::shutdown_both;
+        boost::system::error_code err;
+        host_vst_parameters.shutdown(shutdown_type, err);
+        host_vst_process_replacing.shutdown(shutdown_type, err);
+        host_vst_control.shutdown(shutdown_type, err);
+        host_vst_parameters.close();
+        host_vst_process_replacing.close();
+        host_vst_control.close();
+    }
+
+    /**
+     * Depending on the value of the `listen` argument passed to the
+     * constructor, either accept connections made to the sockets on the Linux
+     * side or connect to the sockets on the Wine side
+     */
+    void connect() {
+        host_vst_dispatch.connect();
+        host_vst_dispatch_midi_events.connect();
+        vst_host_callback.connect();
+        if (acceptors) {
+            acceptors->host_vst_parameters.accept(host_vst_parameters);
+            acceptors->host_vst_process_replacing.accept(
+                host_vst_process_replacing);
+            acceptors->host_vst_control.accept(host_vst_control);
+        } else {
+            host_vst_parameters.connect(host_vst_parameters_endpoint);
+            host_vst_process_replacing.connect(
+                host_vst_process_replacing_endpoint);
+            host_vst_control.connect(host_vst_control_endpoint);
+        }
+    }
+
+    /**
+     * The base directory for our socket endpoints. All `*_endpoint` variables
+     * below are files within this directory.
+     */
+    const boost::filesystem::path base_dir;
+
+    // The naming convention for these sockets is `<from>_<to>_<event>`. For
+    // instance the socket named `host_vst_dispatch` forwards
+    // `AEffect.dispatch()` calls from the native VST host to the Windows VST
+    // plugin (through the Wine VST host).
+
+    /**
+     * The socket that forwards all `dispatcher()` calls from the VST host to
+     * the plugin.
+     */
+    EventHandler<Thread> host_vst_dispatch;
+    /**
+     * Used specifically for the `effProcessEvents` opcode. This is needed
+     * because the Win32 API is designed to block during certain GUI
+     * interactions such as resizing a window or opening a dropdown. Without
+     * this MIDI input would just stop working at times.
+     */
+    EventHandler<Thread> host_vst_dispatch_midi_events;
+    /**
+     * The socket that forwards all `audioMaster()` calls from the Windows VST
+     * plugin to the host.
+     */
+    EventHandler<Thread> vst_host_callback;
+    /**
+     * Used for both `getParameter` and `setParameter` since they mostly
+     * overlap.
+     */
+    boost::asio::local::stream_protocol::socket host_vst_parameters;
+    /**
+     * Used for processing audio usign the `process()`, `processReplacing()` and
+     * `processDoubleReplacing()` functions.
+     */
+    boost::asio::local::stream_protocol::socket host_vst_process_replacing;
+    /**
+     * A control socket that sends data that is not suitable for the other
+     * sockets. At the moment this is only used to, on startup, send the Windows
+     * VST plugin's `AEffect` object to the native VST plugin, and to then send
+     * the configuration (from `config`) back to the Wine host.
+     */
+    boost::asio::local::stream_protocol::socket host_vst_control;
+
+   private:
+    const boost::asio::local::stream_protocol::endpoint
+        host_vst_parameters_endpoint;
+    const boost::asio::local::stream_protocol::endpoint
+        host_vst_process_replacing_endpoint;
+    const boost::asio::local::stream_protocol::endpoint
+        host_vst_control_endpoint;
+
+    /**
+     * All of our socket acceptors. We have to create these before launching the
+     * Wine process.
+     */
+    struct Acceptors {
+        boost::asio::local::stream_protocol::acceptor host_vst_parameters;
+        boost::asio::local::stream_protocol::acceptor
+            host_vst_process_replacing;
+        boost::asio::local::stream_protocol::acceptor host_vst_control;
+    };
+
+    /**
+     * If the `listen` constructor argument was set to `true`, when we'll
+     * prepare a set of socket acceptors that listen on the socket endpoints.
+     */
+    std::optional<Acceptors> acceptors;
+};
+
+/**
+ * Generate a unique base directory that can be used as a prefix for all Unix
+ * domain socket endpoints used in `PluginBridge`/`Vst2Bridge`. This will
+ * usually return `/run/user/<uid>/yabridge-<plugin_name>-<random_id>/`.
+ *
+ * Sockets for group hosts are handled separately. See
+ * `../plugin/utils.h:generate_group_endpoint` for more information on those.
+ *
+ * @param plugin_name The name of the plugin we're generating endpoints for.
+ *   Used as a visual indication of what plugin is using this endpoint.
+ */
+boost::filesystem::path generate_endpoint_base(const std::string& plugin_name);
+
+/**
+ * Create a callback function that takes an `Event` object, decodes the data
+ * into the expected format for VST2 function calls, calls the given function
+ * (either `AEffect::dispatcher()` for host -> plugin events or `audioMaster()`
+ * for plugin -> host events), and serializes the results back into an
+ * `EventResult` object. I'd rather not get too Haskell-y in my C++, but this is
+ * the cleanest solution for this problem.
+ *
+ * This is the receiving analogue of the `*DataCovnerter` objects.
+ *
+ * TODO: Now that `EventHandler::receive` replaced `receive_event()`, refactor
+ *       this to just handle the event directly rather than returning a lambda
+ *
+ * @param plugin The `AEffect` instance that should be passed to the callback
+ *   function.
+ * @param callback The function to call with the arguments received from the
+ *   socket.
+ *
+ * @tparam A function with the same signature as `AEffect::dispatcher` or
+ *   `audioMasterCallback`.
+ *
+ * @return A `EventResult(Event)` callback function that can be passed to
+ * `EditorHandler::receive()`.
+ *
+ * @relates EditorHandler::receive
+ */
+template <typename F>
+auto passthrough_event(AEffect* plugin, F callback) {
+    return [=](Event& event) -> EventResult {
+        // This buffer is used to write strings and small objects to. We'll
+        // initialize the beginning with null values to both prevent it from
+        // being read as some arbitrary C-style string, and to make sure that
+        // `*static_cast<void**>(string_buffer.data)` will be a null pointer if
+        // the plugin is supposed to write a pointer there but doesn't (such as
+        // with `effEditGetRect`/`WantsVstRect`).
+        std::array<char, max_string_length> string_buffer;
+        std::fill(string_buffer.begin(), string_buffer.begin() + sizeof(size_t),
+                  0);
+
+        auto read_payload_fn = overload{
+            [&](const std::nullptr_t&) -> void* { return nullptr; },
+            [&](const std::string& s) -> void* {
+                return const_cast<char*>(s.c_str());
+            },
+            [&](const std::vector<uint8_t>& buffer) -> void* {
+                return const_cast<uint8_t*>(buffer.data());
+            },
+            [&](native_size_t& window_handle) -> void* {
+                // This is the X11 window handle that the editor should reparent
+                // itself to. We have a special wrapper around the dispatch
+                // function that intercepts `effEditOpen` events and creates a
+                // Win32 window and then finally embeds the X11 window Wine
+                // created into this wnidow handle. Make sure to convert the
+                // window ID first to `size_t` in case this is the 32-bit host.
+                return reinterpret_cast<void*>(
+                    static_cast<size_t>(window_handle));
+            },
+            [&](const AEffect&) -> void* { return nullptr; },
+            [&](DynamicVstEvents& events) -> void* {
+                return &events.as_c_events();
+            },
+            [&](DynamicSpeakerArrangement& speaker_arrangement) -> void* {
+                return &speaker_arrangement.as_c_speaker_arrangement();
+            },
+            [&](WantsAEffectUpdate&) -> void* {
+                // The host will never actually ask for an updated `AEffect`
+                // object since that should not be a thing. This is purely a
+                // meant as a workaround for plugins that initialize their
+                // `AEffect` object after the plugin has already finished
+                // initializing.
+                return nullptr;
+            },
+            [&](WantsChunkBuffer&) -> void* { return string_buffer.data(); },
+            [&](VstIOProperties& props) -> void* { return &props; },
+            [&](VstMidiKeyName& key_name) -> void* { return &key_name; },
+            [&](VstParameterProperties& props) -> void* { return &props; },
+            [&](WantsVstRect&) -> void* { return string_buffer.data(); },
+            [&](const WantsVstTimeInfo&) -> void* { return nullptr; },
+            [&](WantsString&) -> void* { return string_buffer.data(); }};
+
+        // Almost all events pass data through the `data` argument. There are
+        // two events, `effSetParameter` and `effGetParameter` that also pass
+        // data through the value argument.
+        void* data = std::visit(read_payload_fn, event.payload);
+        intptr_t value = event.value;
+        if (event.value_payload) {
+            value = reinterpret_cast<intptr_t>(
+                std::visit(read_payload_fn, *event.value_payload));
+        }
+
+        const intptr_t return_value = callback(
+            plugin, event.opcode, event.index, value, data, event.option);
+
+        // Only write back data when needed, this depends on the event payload
+        // type
+        auto write_payload_fn = overload{
+            [&](auto) -> EventResultPayload { return nullptr; },
+            [&](const AEffect& updated_plugin) -> EventResultPayload {
+                // This is a bit of a special case! Instead of writing some
+                // return value, we will update values on the native VST
+                // plugin's `AEffect` object. This is triggered by the
+                // `audioMasterIOChanged` callback from the hosted VST plugin.
+                update_aeffect(*plugin, updated_plugin);
+
+                return nullptr;
+            },
+            [&](DynamicSpeakerArrangement& speaker_arrangement)
+                -> EventResultPayload { return speaker_arrangement; },
+            [&](WantsChunkBuffer&) -> EventResultPayload {
+                // In this case the plugin will have written its data stored in
+                // an array to which a pointer is stored in `data`, with the
+                // return value from the event determines how much data the
+                // plugin has written
+                const uint8_t* chunk_data = *static_cast<uint8_t**>(data);
+                return std::vector<uint8_t>(chunk_data,
+                                            chunk_data + return_value);
+            },
+            [&](VstIOProperties& props) -> EventResultPayload { return props; },
+            [&](VstMidiKeyName& key_name) -> EventResultPayload {
+                return key_name;
+            },
+            [&](VstParameterProperties& props) -> EventResultPayload {
+                return props;
+            },
+            [&](WantsAEffectUpdate&) -> EventResultPayload { return *plugin; },
+            [&](WantsVstRect&) -> EventResultPayload {
+                // The plugin should have written a pointer to a VstRect struct
+                // into the data pointer. I haven't seen this fail yet, but
+                // since some hosts will call `effEditGetRect()` before
+                // `effEditOpen()` I can assume there are plugins that don't
+                // handle this correctly.
+                VstRect* editor_rect = *static_cast<VstRect**>(data);
+                if (!editor_rect) {
+                    return nullptr;
+                }
+
+                return *editor_rect;
+            },
+            [&](WantsVstTimeInfo&) -> EventResultPayload {
+                // Not sure why the VST API has twenty different ways of
+                // returning structs, but in this case the value returned from
+                // the callback function is actually a pointer to a
+                // `VstTimeInfo` struct! It can also be a null pointer if the
+                // host doesn't support this.
+                const auto time_info =
+                    reinterpret_cast<const VstTimeInfo*>(return_value);
+                if (!time_info) {
+                    return nullptr;
+                } else {
+                    return *time_info;
+                }
+            },
+            [&](WantsString&) -> EventResultPayload {
+                return std::string(static_cast<char*>(data));
+            }};
+
+        // As mentioned about, the `effSetSpeakerArrangement` and
+        // `effGetSpeakerArrangement` events are the only two events that use
+        // the value argument as a pointer to write data to. Additionally, the
+        // `effGetSpeakerArrangement` expects the plugin to write its own data
+        // to this value. Hence why we need to encode the response here
+        // separately.
+        const EventResultPayload response_data =
+            std::visit(write_payload_fn, event.payload);
+        std::optional<EventResultPayload> value_response_data = std::nullopt;
+        if (event.value_payload) {
+            value_response_data =
+                std::visit(write_payload_fn, *event.value_payload);
+        }
+
+        EventResult response{.return_value = return_value,
+                             .payload = response_data,
+                             .value_payload = value_response_data};
+
+        return response;
+    };
+}

src/common/configuration.cpp

@@ -84,12 +84,6 @@ Configuration::Configuration(const fs::path& config_path,
                 } else {
                     invalid_options.push_back(key);
                 }
-            } else if (key == "hack_reaper_update_display") {
-                if (const auto parsed_value = value.as_boolean()) {
-                    hack_reaper_update_display = parsed_value->get();
-                } else {
-                    invalid_options.push_back(key);
-                }
             } else if (key == "group") {
                 if (const auto parsed_value = value.as_string()) {
                     group = parsed_value->get();

src/common/configuration.h

@@ -87,14 +87,6 @@ class Configuration {
      */
     bool editor_double_embed = false;
 
-    /**
-     * If this is set to true, then any calls to `audioMasterUpdateDisplay()`
-     * will automatically return 0 without being sent to the host. This is a
-     * HACK to work around implementations issues in REAPER and Renoise, see #29
-     * and #32.
-     */
-    bool hack_reaper_update_display = false;
-
     /**
      * The name of the plugin group that should be used for the plugin this
      * configuration object was created for. If not set, then the plugin should
@@ -128,7 +120,6 @@ class Configuration {
     template <typename S>
     void serialize(S& s) {
         s.value1b(editor_double_embed);
-        s.value1b(hack_reaper_update_display);
         s.ext(group, bitsery::ext::StdOptional(),
               [](S& s, auto& v) { s.text1b(v, 4096); });
         s.ext(matched_file, bitsery::ext::StdOptional(),

src/common/events.h

@@ -1,408 +0,0 @@
-// yabridge: a Wine VST bridge
-// Copyright (C) 2020  Robbert van der Helm
-//
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-#pragma once
-
-#include <mutex>
-
-#include "communication.h"
-#include "logging.h"
-
-/**
- * Encodes the base behavior for reading from and writing to the `data` argument
- * for event dispatch functions. This provides base functionality for these
- * kinds of events. The `dispatch()` function will require some more specific
- * structs.
- */
-class DefaultDataConverter {
-   public:
-    virtual ~DefaultDataConverter(){};
-
-    /**
-     * Read data from the `data` void pointer into a an `EventPayload` value
-     * that can be serialized and conveys the meaning of the event.
-     */
-    virtual EventPayload read(const int /*opcode*/,
-                              const int /*index*/,
-                              const intptr_t /*value*/,
-                              const void* data) const {
-        if (!data) {
-            return nullptr;
-        }
-
-        // This is a simple fallback that will work in almost every case.
-        // Because some plugins don't zero out their string buffers when sending
-        // host callbacks, we will explicitely list all callbacks that expect a
-        // string in `DispatchDataConverter` adn `HostCallbackDataConverter`.
-        const char* c_string = static_cast<const char*>(data);
-        if (c_string[0] != 0) {
-            return std::string(c_string);
-        } else {
-            return WantsString{};
-        }
-    }
-
-    /**
-     * Read data from the `value` pointer into a an `EventPayload` value that
-     * can be serialized and conveys the meaning of the event. This is only used
-     * for the `effSetSpeakerArrangement` and `effGetSpeakerArrangement` events.
-     */
-    virtual std::optional<EventPayload> read_value(
-        const int /*opcode*/,
-        const intptr_t /*value*/) const {
-        return std::nullopt;
-    }
-
-    /**
-     * Write the reponse back to the `data` pointer.
-     */
-    virtual void write(const int /*opcode*/,
-                       void* data,
-                       const EventResult& response) const {
-        // The default behavior is to handle this as a null terminated C-style
-        // string
-        std::visit(overload{[&](const auto&) {},
-                            [&](const std::string& s) {
-                                char* output = static_cast<char*>(data);
-
-                                // We use std::string for easy transport but in
-                                // practice we're always writing null terminated
-                                // C-style strings
-                                std::copy(s.begin(), s.end(), output);
-                                output[s.size()] = 0;
-                            }},
-                   response.payload);
-    }
-
-    /**
-     * Write the reponse back to the `value` pointer. This is only used during
-     * the `effGetSpeakerArrangement` event.
-     */
-    virtual void write_value(const int /*opcode*/,
-                             intptr_t /*value*/,
-                             const EventResult& /*response*/) const {}
-
-    /**
-     * This function can override a callback's return value based on the opcode.
-     * This is used in one place to return a pointer to a `VstTime` object
-     * that's contantly being updated.
-     *
-     * @param opcode The opcode for the current event.
-     * @param original The original return value as returned by the callback
-     *   function.
-     */
-    virtual intptr_t return_value(const int /*opcode*/,
-                                  const intptr_t original) const {
-        return original;
-    }
-};
-
-/**
- * Serialize and send an event over a socket. This is used for both the host ->
- * plugin 'dispatch' events and the plugin -> host 'audioMaster' host callbacks
- * since they follow the same format. See one of those functions for details on
- * the parameters and return value of this function.
- *
- * @param socket The socket to write over, should be the same socket the other
- *   endpoint is using to call `receive_event()`.
- * @param write_mutex A mutex to ensure that only one thread can write to
- *   the socket at once. Needed because VST hosts and plugins can and sometimes
- *   will call the `dispatch()` or `audioMaster()` functions from multiple
- *   threads at once.
- * @param data_converter Some struct that knows how to read data from and write
- *   data back to the `data` void pointer. For host callbacks this parameter
- *   contains either a string or a null pointer while `dispatch()` calls might
- *   contain opcode specific structs. See the documentation for `EventPayload`
- *   for more information. The `DefaultDataConverter` defined above handles the
- *   basic behavior that's sufficient for host callbacks.
- * @param logging A pair containing a logger instance and whether or not this is
- *   for sending `dispatch()` events or host callbacks. Optional since it
- *   doesn't have to be done on both sides.
- *
- * @relates receive_event
- * @relates passthrough_event
- */
-template <typename D>
-intptr_t send_event(boost::asio::local::stream_protocol::socket& socket,
-                    std::mutex& write_mutex,
-                    D& data_converter,
-                    std::optional<std::pair<Logger&, bool>> logging,
-                    int opcode,
-                    int index,
-                    intptr_t value,
-                    void* data,
-                    float option) {
-    // Encode the right payload types for this event. Check the documentation
-    // for `EventPayload` for more information. These types are converted to
-    // C-style data structures in `passthrough_event()` so they can be passed to
-    // a plugin or callback function.
-    const EventPayload payload =
-        data_converter.read(opcode, index, value, data);
-    const std::optional<EventPayload> value_payload =
-        data_converter.read_value(opcode, value);
-
-    if (logging) {
-        auto [logger, is_dispatch] = *logging;
-        logger.log_event(is_dispatch, opcode, index, value, payload, option,
-                         value_payload);
-    }
-
-    const Event event{.opcode = opcode,
-                      .index = index,
-                      .value = value,
-                      .option = option,
-                      .payload = payload,
-                      .value_payload = value_payload};
-
-    // Prevent two threads from writing over the socket at the same time and
-    // messages getting out of order. This is needed because we can't prevent
-    // the plugin or the host from calling `dispatch()` or `audioMaster()` from
-    // multiple threads.
-    EventResult response;
-    {
-        std::lock_guard lock(write_mutex);
-        write_object(socket, event);
-        response = read_object<EventResult>(socket);
-    }
-
-    if (logging) {
-        auto [logger, is_dispatch] = *logging;
-        logger.log_event_response(is_dispatch, opcode, response.return_value,
-                                  response.payload, response.value_payload);
-    }
-
-    data_converter.write(opcode, data, response);
-    data_converter.write_value(opcode, value, response);
-
-    return data_converter.return_value(opcode, response.return_value);
-}
-
-/**
- * Receive an event from a socket, call a function to generate a response, and
- * write the response back over the socket. This is usually used together with
- * `passthrough_event()` which passes the event data through to an event
- * dispatcher function. This behaviour is split into two functions to avoid
- * redundant data conversions when handling MIDI data, as some plugins require
- * the received data to be temporarily stored until the next event audio buffer
- * gets processed.
- *
- * @param socket The socket to receive on and to send the response back to.
- * @param logging A pair containing a logger instance and whether or not this is
- *   for sending `dispatch()` events or host callbacks. Optional since it
- *   doesn't have to be done on both sides.
- * @param callback The function used to generate a response out of an event.
- *
- * @tparam F A function type in the form of `EventResponse(Event)`.
- *
- * @relates send_event
- * @relates passthrough_event
- */
-template <typename F>
-void receive_event(boost::asio::local::stream_protocol::socket& socket,
-                   std::optional<std::pair<Logger&, bool>> logging,
-                   F callback) {
-    auto event = read_object<Event>(socket);
-    if (logging) {
-        auto [logger, is_dispatch] = *logging;
-        logger.log_event(is_dispatch, event.opcode, event.index, event.value,
-                         event.payload, event.option, event.value_payload);
-    }
-
-    EventResult response = callback(event);
-    if (logging) {
-        auto [logger, is_dispatch] = *logging;
-        logger.log_event_response(is_dispatch, event.opcode,
-                                  response.return_value, response.payload,
-                                  response.value_payload);
-    }
-
-    write_object(socket, response);
-}
-
-/**
- * Create a callback function that takes an `Event` object, decodes the data
- * into the expected format for VST2 function calls, calls the given function
- * (either `AEffect::dispatcher()` for host -> plugin events or `audioMaster()`
- * for plugin -> host events), and serializes the results back into an
- * `EventResult` object. I'd rather not get too Haskell-y in my C++, but this is
- * the cleanest solution for this problem.
- *
- * This is the receiving analogue of the `*DataCovnerter` objects.
- *
- * @param plugin The `AEffect` instance that should be passed to the callback
- *   function.
- * @param callback The function to call with the arguments received from the
- *   socket.
- *
- * @tparam A function with the same signature as `AEffect::dispatcher` or
- *   `audioMasterCallback`.
- *
- * @return A `EventResult(Event)` callback function that can be passed to
- * `receive_event`.
- *
- * @relates receive_event
- */
-template <typename F>
-auto passthrough_event(AEffect* plugin, F callback) {
-    return [=](Event& event) -> EventResult {
-        // This buffer is used to write strings and small objects to. We'll
-        // initialize the beginning with null values to both prevent it from
-        // being read as some arbitrary C-style string, and to make sure that
-        // `*static_cast<void**>(string_buffer.data)` will be a null pointer if
-        // the plugin is supposed to write a pointer there but doesn't (such as
-        // with `effEditGetRect`/`WantsVstRect`).
-        std::array<char, max_string_length> string_buffer;
-        std::fill(string_buffer.begin(), string_buffer.begin() + sizeof(size_t),
-                  0);
-
-        auto read_payload_fn = overload{
-            [&](const std::nullptr_t&) -> void* { return nullptr; },
-            [&](const std::string& s) -> void* {
-                return const_cast<char*>(s.c_str());
-            },
-            [&](const std::vector<uint8_t>& buffer) -> void* {
-                return const_cast<uint8_t*>(buffer.data());
-            },
-            [&](native_size_t& window_handle) -> void* {
-                // This is the X11 window handle that the editor should reparent
-                // itself to. We have a special wrapper around the dispatch
-                // function that intercepts `effEditOpen` events and creates a
-                // Win32 window and then finally embeds the X11 window Wine
-                // created into this wnidow handle. Make sure to convert the
-                // window ID first to `size_t` in case this is the 32-bit host.
-                return reinterpret_cast<void*>(
-                    static_cast<size_t>(window_handle));
-            },
-            [&](const AEffect&) -> void* { return nullptr; },
-            [&](DynamicVstEvents& events) -> void* {
-                return &events.as_c_events();
-            },
-            [&](DynamicSpeakerArrangement& speaker_arrangement) -> void* {
-                return &speaker_arrangement.as_c_speaker_arrangement();
-            },
-            [&](WantsAEffectUpdate&) -> void* {
-                // The host will never actually ask for an updated `AEffect`
-                // object since that should not be a thing. This is purely a
-                // meant as a workaround for plugins that initialize their
-                // `AEffect` object after the plugin has already finished
-                // initializing.
-                return nullptr;
-            },
-            [&](WantsChunkBuffer&) -> void* { return string_buffer.data(); },
-            [&](VstIOProperties& props) -> void* { return &props; },
-            [&](VstMidiKeyName& key_name) -> void* { return &key_name; },
-            [&](VstParameterProperties& props) -> void* { return &props; },
-            [&](WantsVstRect&) -> void* { return string_buffer.data(); },
-            [&](const WantsVstTimeInfo&) -> void* { return nullptr; },
-            [&](WantsString&) -> void* { return string_buffer.data(); }};
-
-        // Almost all events pass data through the `data` argument. There are
-        // two events, `effSetParameter` and `effGetParameter` that also pass
-        // data through the value argument.
-        void* data = std::visit(read_payload_fn, event.payload);
-        intptr_t value = event.value;
-        if (event.value_payload) {
-            value = reinterpret_cast<intptr_t>(
-                std::visit(read_payload_fn, *event.value_payload));
-        }
-
-        const intptr_t return_value = callback(
-            plugin, event.opcode, event.index, value, data, event.option);
-
-        // Only write back data when needed, this depends on the event payload
-        // type
-        auto write_payload_fn = overload{
-            [&](auto) -> EventResultPayload { return nullptr; },
-            [&](const AEffect& updated_plugin) -> EventResultPayload {
-                // This is a bit of a special case! Instead of writing some
-                // return value, we will update values on the native VST
-                // plugin's `AEffect` object. This is triggered by the
-                // `audioMasterIOChanged` callback from the hosted VST plugin.
-                update_aeffect(*plugin, updated_plugin);
-
-                return nullptr;
-            },
-            [&](DynamicSpeakerArrangement& speaker_arrangement)
-                -> EventResultPayload { return speaker_arrangement; },
-            [&](WantsChunkBuffer&) -> EventResultPayload {
-                // In this case the plugin will have written its data stored in
-                // an array to which a pointer is stored in `data`, with the
-                // return value from the event determines how much data the
-                // plugin has written
-                const uint8_t* chunk_data = *static_cast<uint8_t**>(data);
-                return std::vector<uint8_t>(chunk_data,
-                                            chunk_data + return_value);
-            },
-            [&](VstIOProperties& props) -> EventResultPayload { return props; },
-            [&](VstMidiKeyName& key_name) -> EventResultPayload {
-                return key_name;
-            },
-            [&](VstParameterProperties& props) -> EventResultPayload {
-                return props;
-            },
-            [&](WantsAEffectUpdate&) -> EventResultPayload { return *plugin; },
-            [&](WantsVstRect&) -> EventResultPayload {
-                // The plugin should have written a pointer to a VstRect struct
-                // into the data pointer. I haven't seen this fail yet, but
-                // since some hosts will call `effEditGetRect()` before
-                // `effEditOpen()` I can assume there are plugins that don't
-                // handle this correctly.
-                VstRect* editor_rect = *static_cast<VstRect**>(data);
-                if (!editor_rect) {
-                    return nullptr;
-                }
-
-                return *editor_rect;
-            },
-            [&](WantsVstTimeInfo&) -> EventResultPayload {
-                // Not sure why the VST API has twenty different ways of
-                // returning structs, but in this case the value returned from
-                // the callback function is actually a pointer to a
-                // `VstTimeInfo` struct! It can also be a null pointer if the
-                // host doesn't support this.
-                const auto time_info =
-                    reinterpret_cast<const VstTimeInfo*>(return_value);
-                if (!time_info) {
-                    return nullptr;
-                } else {
-                    return *time_info;
-                }
-            },
-            [&](WantsString&) -> EventResultPayload {
-                return std::string(static_cast<char*>(data));
-            }};
-
-        // As mentioned about, the `effSetSpeakerArrangement` and
-        // `effGetSpeakerArrangement` events are the only two events that use
-        // the value argument as a pointer to write data to. Additionally, the
-        // `effGetSpeakerArrangement` expects the plugin to write its own data
-        // to this value. Hence why we need to encode the response here
-        // separately.
-        const EventResultPayload response_data =
-            std::visit(write_payload_fn, event.payload);
-        std::optional<EventResultPayload> value_response_data = std::nullopt;
-        if (event.value_payload) {
-            value_response_data =
-                std::visit(write_payload_fn, *event.value_payload);
-        }
-
-        EventResult response{.return_value = return_value,
-                             .payload = response_data,
-                             .value_payload = value_response_data};
-
-        return response;
-    };
-}

src/common/logging.h

@@ -97,8 +97,9 @@ class Logger {
     void log_get_parameter_response(float vlaue);
     void log_set_parameter(int index, float value);
     void log_set_parameter_response();
-    // If is_dispatch is true, then use opcode names from the plugin's dispatch
-    // function. Otherwise use names for the host callback function opcodes.
+    // If `is_dispatch` is `true`, then use opcode names from the plugin's
+    // dispatch function. Otherwise use names for the host callback function
+    // opcodes.
     void log_event(bool is_dispatch,
                    int opcode,
                    int index,

src/common/serialization.cpp

@@ -108,7 +108,3 @@ AEffect& update_aeffect(AEffect& plugin, const AEffect& updated_plugin) {
 
     return plugin;
 }
-
-bool GroupRequest::operator==(const GroupRequest& rhs) const {
-    return plugin_path == rhs.plugin_path && socket_path == rhs.socket_path;
-}

src/common/serialization.h

@@ -598,14 +598,12 @@ struct AudioBuffers {
  */
 struct GroupRequest {
     std::string plugin_path;
-    std::string socket_path;
-
-    bool operator==(const GroupRequest& rhs) const;
+    std::string endpoint_base_dir;
 
     template <typename S>
     void serialize(S& s) {
         s.text1b(plugin_path, 4096);
-        s.text1b(socket_path, 4096);
+        s.text1b(endpoint_base_dir, 4096);
     }
 };
 
@@ -614,7 +612,8 @@ struct std::hash<GroupRequest> {
     std::size_t operator()(GroupRequest const& params) const noexcept {
         std::hash<string> hasher{};
 
-        return hasher(params.plugin_path) ^ (hasher(params.socket_path) << 1);
+        return hasher(params.plugin_path) ^
+               (hasher(params.endpoint_base_dir) << 1);
     }
 };
 

src/common/utils.cpp

@@ -17,6 +17,19 @@
 #include "utils.h"
 
 #include <sched.h>
+#include <boost/process/environment.hpp>
+
+namespace bp = boost::process;
+namespace fs = boost::filesystem;
+
+fs::path get_temporary_directory() {
+    bp::environment env = boost::this_process::environment();
+    if (!env["XDG_RUNTIME_DIR"].empty()) {
+        return env["XDG_RUNTIME_DIR"].to_string();
+    } else {
+        return fs::temp_directory_path();
+    }
+}
 
 bool set_realtime_priority() {
     sched_param params{.sched_priority = 5};

src/common/utils.h

@@ -16,6 +16,17 @@
 
 #pragma once
 
+#ifdef __WINE__
+#include "../wine-host/boost-fix.h"
+#endif
+#include <boost/filesystem.hpp>
+
+/**
+ * Return the path to the directory for story temporary files. This will be
+ * `$XDG_RUNTIME_DIR` if set, and `/tmp` otherwise.
+ */
+boost::filesystem::path get_temporary_directory();
+
 /**
  * Set the scheduling policy to `SCHED_FIFO` with priority 10 for this process.
  * We explicitly don't do this for wineserver itself since from my testing that

src/plugin/host-process.cpp

@@ -83,7 +83,7 @@ void HostProcess::async_log_pipe_lines(patched_async_pipe& pipe,
 IndividualHost::IndividualHost(boost::asio::io_context& io_context,
                                Logger& logger,
                                fs::path plugin_path,
-                               fs::path socket_endpoint)
+                               const Sockets<std::jthread>& sockets)
     : HostProcess(io_context, logger),
       plugin_arch(find_vst_architecture(plugin_path)),
       host_path(find_vst_host(plugin_arch, false)),
@@ -93,7 +93,7 @@ IndividualHost::IndividualHost(boost::asio::io_context& io_context,
 #else
                        plugin_path,
 #endif
-                       socket_endpoint,
+                       sockets.base_dir,
                        bp::env = set_wineprefix(),
                        bp::std_out = stdout_pipe,
                        bp::std_err = stderr_pipe
@@ -104,7 +104,7 @@ IndividualHost::IndividualHost(boost::asio::io_context& io_context,
 #endif
                            )) {
 #ifdef WITH_WINEDBG
-    if (plugin_path.string().find(' ') != std::string::npos) {
+    if (plugin_path.filename().string().find(' ') != std::string::npos) {
         logger.log("Warning: winedbg does not support paths containing spaces");
     }
 #endif
@@ -127,17 +127,15 @@ void IndividualHost::terminate() {
     host.wait();
 }
 
-GroupHost::GroupHost(
-    boost::asio::io_context& io_context,
-    Logger& logger,
-    fs::path plugin_path,
-    fs::path socket_endpoint,
-    std::string group_name,
-    boost::asio::local::stream_protocol::socket& host_vst_dispatch)
+GroupHost::GroupHost(boost::asio::io_context& io_context,
+                     Logger& logger,
+                     fs::path plugin_path,
+                     Sockets<std::jthread>& sockets,
+                     std::string group_name)
     : HostProcess(io_context, logger),
       plugin_arch(find_vst_architecture(plugin_path)),
       host_path(find_vst_host(plugin_arch, true)),
-      host_vst_dispatch(host_vst_dispatch) {
+      sockets(sockets) {
 #ifdef WITH_WINEDBG
     if (plugin_path.string().find(' ') != std::string::npos) {
         logger.log("Warning: winedbg does not support paths containing spaces");
@@ -167,6 +165,7 @@ GroupHost::GroupHost(
         wine_prefix = fs::path(host_env.at("HOME").to_string()) / ".wine";
     }
 
+    const fs::path endpoint_base_dir = sockets.base_dir;
     const fs::path group_socket_path =
         generate_group_endpoint(group_name, wine_prefix, plugin_arch);
     try {
@@ -175,9 +174,10 @@ GroupHost::GroupHost(
         boost::asio::local::stream_protocol::socket group_socket(io_context);
         group_socket.connect(group_socket_path.string());
 
-        write_object(group_socket,
-                     GroupRequest{.plugin_path = plugin_path.string(),
-                                  .socket_path = socket_endpoint.string()});
+        write_object(
+            group_socket,
+            GroupRequest{.plugin_path = plugin_path.string(),
+                         .endpoint_base_dir = endpoint_base_dir.string()});
         const auto response = read_object<GroupResponse>(group_socket);
 
         host_pid = response.pid;
@@ -199,7 +199,7 @@ GroupHost::GroupHost(
         // meantime.
         group_host_connect_handler = std::jthread([&, group_socket_path,
                                                    plugin_path,
-                                                   socket_endpoint]() {
+                                                   endpoint_base_dir]() {
             using namespace std::literals::chrono_literals;
 
             // TODO: Replace this polling with inotify
@@ -214,8 +214,9 @@ GroupHost::GroupHost(
 
                     write_object(
                         group_socket,
-                        GroupRequest{.plugin_path = plugin_path.string(),
-                                     .socket_path = socket_endpoint.string()});
+                        GroupRequest{
+                            .plugin_path = plugin_path.string(),
+                            .endpoint_base_dir = endpoint_base_dir.string()});
                     const auto response =
                         read_object<GroupResponse>(group_socket);
 
@@ -262,7 +263,5 @@ void GroupHost::terminate() {
     // There's no need to manually terminate group host processes as they will
     // shut down automatically after all plugins have exited. Manually closing
     // the dispatch socket will cause the associated plugin to exit.
-    host_vst_dispatch.shutdown(
-        boost::asio::local::stream_protocol::socket::shutdown_both);
-    host_vst_dispatch.close();
+    sockets.host_vst_dispatch.close();
 }

src/plugin/host-process.h

@@ -25,6 +25,7 @@
 #include <boost/process/child.hpp>
 #include <thread>
 
+#include "../common/communication.h"
 #include "../common/logging.h"
 #include "utils.h"
 
@@ -117,7 +118,7 @@ class IndividualHost : public HostProcess {
      *   handled on.
      * @param logger The `Logger` instance the redirected STDIO streams will be
      *   written to.
-     * @param socket_endpoint The endpoint that should be used to communicate
+     * @param sockets The socket endpoints that will be used for communication
      *   with the plugin.
      *
      * @throw std::runtime_error When `plugin_path` does not point to a valid
@@ -126,7 +127,7 @@ class IndividualHost : public HostProcess {
     IndividualHost(boost::asio::io_context& io_context,
                    Logger& logger,
                    boost::filesystem::path plugin_path,
-                   boost::filesystem::path socket_endpoint);
+                   const Sockets<std::jthread>& sockets);
 
     PluginArchitecture architecture() override;
     boost::filesystem::path path() override;
@@ -160,19 +161,16 @@ class GroupHost : public HostProcess {
      *   handled on.
      * @param logger The `Logger` instance the redirected STDIO streams will be
      *   written to.
-     * @param socket_endpoint The endpoint that should be used to communicate
-     *   with the plugin.
+     * @param sockets The socket endpoints that will be used for communication
+     *   with the plugin. When the plugin shuts down, we'll terminate the
+     *   dispatch socket contained in this object.
      * @param group_name The name of the plugin group.
-     * @param host_vst_dispatch The socket used to communicate
-     *   `AEffect::dispatcher()` events with this plugin. Will be closed as to
-     *   shut down the plugin.
      */
     GroupHost(boost::asio::io_context& io_context,
               Logger& logger,
               boost::filesystem::path plugin_path,
-              boost::filesystem::path socket_endpoint,
-              std::string group_name,
-              boost::asio::local::stream_protocol::socket& host_vst_dispatch);
+              Sockets<std::jthread>& socket_endpoint,
+              std::string group_name);
 
     PluginArchitecture architecture() override;
     boost::filesystem::path path() override;
@@ -191,10 +189,10 @@ class GroupHost : public HostProcess {
     pid_t host_pid;
 
     /**
-     * The associated dispatch socket for the plugin we're hosting. This is used
-     * to terminate the plugin.
+     * The associated sockets for the plugin we're hosting. This is used to
+     * terminate the plugin.
      */
-    boost::asio::local::stream_protocol::socket& host_vst_dispatch;
+    Sockets<std::jthread>& sockets;
 
     /**
      * A thread that waits for the group host to have started and then ask it to

src/plugin/plugin-bridge.cpp

@@ -21,7 +21,6 @@
 #include <src/common/config/version.h>
 
 #include "../common/communication.h"
-#include "../common/events.h"
 #include "../common/utils.h"
 #include "utils.h"
 
@@ -54,32 +53,26 @@ PluginBridge::PluginBridge(audioMasterCallback host_callback)
       // bridge will crash otherwise
       plugin(),
       io_context(),
-      socket_endpoint(generate_plugin_endpoint().string()),
-      socket_acceptor(io_context, socket_endpoint),
-      host_vst_dispatch(io_context),
-      host_vst_dispatch_midi_events(io_context),
-      vst_host_callback(io_context),
-      host_vst_parameters(io_context),
-      host_vst_process_replacing(io_context),
-      host_vst_control(io_context),
+      sockets(io_context,
+              generate_endpoint_base(
+                  vst_plugin_path.filename().replace_extension("").string()),
+              true),
       host_callback_function(host_callback),
       logger(Logger::create_from_environment(
-          create_logger_prefix(socket_endpoint.path()))),
+          create_logger_prefix(sockets.base_dir))),
       wine_version(get_wine_version()),
-      vst_host(
-          config.group
-              ? std::unique_ptr<HostProcess>(
-                    std::make_unique<GroupHost>(io_context,
-                                                logger,
-                                                vst_plugin_path,
-                                                socket_endpoint.path(),
-                                                *config.group,
-                                                host_vst_dispatch))
-              : std::unique_ptr<HostProcess>(
-                    std::make_unique<IndividualHost>(io_context,
+      vst_host(config.group
+                   ? std::unique_ptr<HostProcess>(
+                         std::make_unique<GroupHost>(io_context,
                                                      logger,
                                                      vst_plugin_path,
-                                                     socket_endpoint.path()))),
+                                                     sockets,
+                                                     *config.group))
+                   : std::unique_ptr<HostProcess>(
+                         std::make_unique<IndividualHost>(io_context,
+                                                          logger,
+                                                          vst_plugin_path,
+                                                          sockets))),
       has_realtime_priority(set_realtime_priority()),
       wine_io_handler([&]() { io_context.run(); }) {
     log_init_message();
@@ -107,24 +100,13 @@ PluginBridge::PluginBridge(audioMasterCallback host_callback)
     });
 #endif
 
-    // It's very important that these sockets are connected to in the same
-    // order in the Wine VST host
-    socket_acceptor.accept(host_vst_dispatch);
-    socket_acceptor.accept(host_vst_dispatch_midi_events);
-    socket_acceptor.accept(vst_host_callback);
-    socket_acceptor.accept(host_vst_parameters);
-    socket_acceptor.accept(host_vst_process_replacing);
-    socket_acceptor.accept(host_vst_control);
-
+    // This will block until all sockets have been connected to by the Wine VST
+    // host
+    sockets.connect();
 #ifndef WITH_WINEDBG
     host_guard_handler.request_stop();
 #endif
 
-    // There's no need to keep the socket endpoint file around after accepting
-    // all the sockets, and RAII won't clean these files up for us
-    socket_acceptor.close();
-    fs::remove(socket_endpoint.path());
-
     // Set up all pointers for our `AEffect` struct. We will fill this with data
     // from the VST plugin loaded in Wine at the end of this constructor.
     plugin.ptr3 = this;
@@ -139,41 +121,30 @@ PluginBridge::PluginBridge(audioMasterCallback host_callback)
     // instead of asynchronous IO since communication has to be handled in
     // lockstep anyway
     host_callback_handler = std::jthread([&]() {
-        while (true) {
-            try {
-                // TODO: Think of a nicer way to structure this and the similar
-                //       handler in `Vst2Bridge::handle_dispatch_midi_events`
-                receive_event(
-                    vst_host_callback, std::pair<Logger&, bool>(logger, false),
-                    [&](Event& event) {
-                        // MIDI events sent from the plugin back to the host are
-                        // a special case here. They have to sent during the
-                        // `processReplacing()` function or else the host will
-                        // ignore them. Because of this we'll temporarily save
-                        // any MIDI events we receive here, and then we'll
-                        // actually send them to the host at the end of the
-                        // `process_replacing()` function.
-                        if (event.opcode == audioMasterProcessEvents) {
-                            std::lock_guard lock(incoming_midi_events_mutex);
+        sockets.vst_host_callback.receive(
+            std::pair<Logger&, bool>(logger, false),
+            [&](Event& event, bool /*on_main_thread*/) {
+                // MIDI events sent from the plugin back to the host are a
+                // special case here. They have to sent during the
+                // `processReplacing()` function or else the host will ignore
+                // them. Because of this we'll temporarily save any MIDI events
+                // we receive here, and then we'll actually send them to the
+                // host at the end of the `process_replacing()` function.
+                if (event.opcode == audioMasterProcessEvents) {
+                    std::lock_guard lock(incoming_midi_events_mutex);
 
-                            incoming_midi_events.push_back(
-                                std::get<DynamicVstEvents>(event.payload));
-                            EventResult response{.return_value = 1,
-                                                 .payload = nullptr,
-                                                 .value_payload = std::nullopt};
+                    incoming_midi_events.push_back(
+                        std::get<DynamicVstEvents>(event.payload));
+                    EventResult response{.return_value = 1,
+                                         .payload = nullptr,
+                                         .value_payload = std::nullopt};
 
-                            return response;
-                        } else {
-                            return passthrough_event(
-                                &plugin, host_callback_function)(event);
-                        }
-                    });
-            } catch (const boost::system::system_error&) {
-                // This happens when the sockets got closed because the plugin
-                // is being shut down
-                break;
-            }
-        }
+                    return response;
+                } else {
+                    return passthrough_event(&plugin,
+                                             host_callback_function)(event);
+                }
+            });
     });
 
     // Read the plugin's information from the Wine process. This can only be
@@ -181,13 +152,14 @@ PluginBridge::PluginBridge(audioMasterCallback host_callback)
     // call these during its initialization. Any further updates will be sent
     // over the `dispatcher()` socket. This would happen whenever the plugin
     // calls `audioMasterIOChanged()` and after the host calls `effOpen()`.
-    const auto initialization_data = read_object<EventResult>(host_vst_control);
+    const auto initialization_data =
+        read_object<EventResult>(sockets.host_vst_control);
     const auto initialized_plugin =
         std::get<AEffect>(initialization_data.payload);
 
     // After receiving the `AEffect` values we'll want to send the configuration
     // back to complete the startup process
-    write_object(host_vst_control, config);
+    write_object(sockets.host_vst_control, config);
 
     update_aeffect(plugin, initialized_plugin);
 }
@@ -452,10 +424,9 @@ intptr_t PluginBridge::dispatch(AEffect* /*plugin*/,
             intptr_t return_value = 0;
             try {
                 // TODO: Add some kind of timeout?
-                return_value =
-                    send_event(host_vst_dispatch, dispatch_mutex, converter,
-                               std::pair<Logger&, bool>(logger, true), opcode,
-                               index, value, data, option);
+                return_value = sockets.host_vst_dispatch.send(
+                    converter, std::pair<Logger&, bool>(logger, true), opcode,
+                    index, value, data, option);
             } catch (const boost::system::system_error& a) {
                 // Thrown when the socket gets closed because the VST plugin
                 // loaded into the Wine process crashed during shutdown
@@ -478,10 +449,9 @@ intptr_t PluginBridge::dispatch(AEffect* /*plugin*/,
             // thread and socket to pass MIDI events. Otherwise plugins will
             // stop receiving MIDI data when they have an open dropdowns or
             // message box.
-            return send_event(host_vst_dispatch_midi_events,
-                              dispatch_midi_events_mutex, converter,
-                              std::pair<Logger&, bool>(logger, true), opcode,
-                              index, value, data, option);
+            return sockets.host_vst_dispatch_midi_events.send(
+                converter, std::pair<Logger&, bool>(logger, true), opcode,
+                index, value, data, option);
             break;
         case effCanDo: {
             const std::string query(static_cast<const char*>(data));
@@ -503,29 +473,6 @@ intptr_t PluginBridge::dispatch(AEffect* /*plugin*/,
                 logger.log("   when using REAPER.");
                 logger.log("");
 
-                // Since the user is using REAPER, also show a reminder that the
-                // REAPER workaround should be enabled when it is not yet
-                // enabled since it may be easy to miss
-                if (!config.hack_reaper_update_display) {
-                    logger.log(
-                        "   With using REAPER you will have to enable the");
-                    logger.log(
-                        "   'hack_reaper_update_display' option to prevent");
-                    logger.log(
-                        "   certain plugins from crashing. To do so, create a");
-                    logger.log(
-                        "   new file named 'yabridge.toml' next to your");
-                    logger.log("   plugins with the following contents:");
-                    logger.log("");
-                    logger.log(
-                        "   # "
-                        "https://github.com/robbert-vdh/"
-                        "yabridge#runtime-dependencies-and-known-issues");
-                    logger.log("   [\"*\"]");
-                    logger.log("   hack_reaper_update_display = true");
-                    logger.log("");
-                }
-
                 logger.log_event_response(true, opcode, -1, nullptr,
                                           std::nullopt);
                 return -1;
@@ -538,9 +485,9 @@ intptr_t PluginBridge::dispatch(AEffect* /*plugin*/,
     // and loading plugin state it's much better to have bitsery or our
     // receiving function temporarily allocate a large enough buffer rather than
     // to have a bunch of allocated memory sitting around doing nothing.
-    return send_event(host_vst_dispatch, dispatch_mutex, converter,
-                      std::pair<Logger&, bool>(logger, true), opcode, index,
-                      value, data, option);
+    return sockets.host_vst_dispatch.send(
+        converter, std::pair<Logger&, bool>(logger, true), opcode, index, value,
+        data, option);
 }
 
 template <typename T>
@@ -555,11 +502,11 @@ void PluginBridge::do_process(T** inputs, T** outputs, int sample_frames) {
     }
 
     const AudioBuffers request{input_buffers, sample_frames};
-    write_object(host_vst_process_replacing, request, process_buffer);
+    write_object(sockets.host_vst_process_replacing, request, process_buffer);
 
     // Write the results back to the `outputs` arrays
-    const auto response =
-        read_object<AudioBuffers>(host_vst_process_replacing, process_buffer);
+    const auto response = read_object<AudioBuffers>(
+        sockets.host_vst_process_replacing, process_buffer);
     const auto& response_buffers =
         std::get<std::vector<std::vector<T>>>(response.buffers);
 
@@ -608,8 +555,8 @@ float PluginBridge::get_parameter(AEffect* /*plugin*/, int index) {
     // called at the same time since  they share the same socket
     {
         std::lock_guard lock(parameters_mutex);
-        write_object(host_vst_parameters, request);
-        response = read_object<ParameterResult>(host_vst_parameters);
+        write_object(sockets.host_vst_parameters, request);
+        response = read_object<ParameterResult>(sockets.host_vst_parameters);
     }
 
     logger.log_get_parameter_response(*response.value);
@@ -625,9 +572,9 @@ void PluginBridge::set_parameter(AEffect* /*plugin*/, int index, float value) {
 
     {
         std::lock_guard lock(parameters_mutex);
-        write_object(host_vst_parameters, request);
+        write_object(sockets.host_vst_parameters, request);
 
-        response = read_object<ParameterResult>(host_vst_parameters);
+        response = read_object<ParameterResult>(sockets.host_vst_parameters);
     }
 
     logger.log_set_parameter_response();
@@ -647,7 +594,8 @@ void PluginBridge::log_init_message() {
              << std::endl;
     init_msg << "realtime:     '" << (has_realtime_priority ? "yes" : "no")
              << "'" << std::endl;
-    init_msg << "socket:       '" << socket_endpoint.path() << "'" << std::endl;
+    init_msg << "sockets:      '" << sockets.base_dir.string() << "'"
+             << std::endl;
     init_msg << "wine prefix:  '";
 
     // If the Wine prefix is manually overridden, then this should be made
@@ -689,10 +637,6 @@ void PluginBridge::log_init_message() {
     if (config.editor_double_embed) {
         other_options.push_back("editor: double embed");
     }
-    if (config.hack_reaper_update_display) {
-        other_options.push_back(
-            "hack: REAPER audioMasterUpdateDisplay() workaround");
-    }
     if (!other_options.empty()) {
         init_msg << join_quoted_strings(other_options) << std::endl;
     } else {

src/plugin/plugin-bridge.h

@@ -23,6 +23,7 @@
 #include <mutex>
 #include <thread>
 
+#include "../common/communication.h"
 #include "../common/configuration.h"
 #include "../common/logging.h"
 #include "host-process.h"
@@ -123,45 +124,7 @@ class PluginBridge {
     void log_init_message();
 
     boost::asio::io_context io_context;
-    boost::asio::local::stream_protocol::endpoint socket_endpoint;
-    boost::asio::local::stream_protocol::acceptor socket_acceptor;
-
-    // The naming convention for these sockets is `<from>_<to>_<event>`. For
-    // instance the socket named `host_vst_dispatch` forwards
-    // `AEffect.dispatch()` calls from the native VST host to the Windows VST
-    // plugin (through the Wine VST host).
-
-    /**
-     * The socket that forwards all `dispatcher()` calls from the VST host to
-     * the plugin.
-     */
-    boost::asio::local::stream_protocol::socket host_vst_dispatch;
-    /**
-     * Used specifically for the `effProcessEvents` opcode. This is needed
-     * because the Win32 API is designed to block during certain GUI
-     * interactions such as resizing a window or opening a dropdown. Without
-     * this MIDI input would just stop working at times.
-     */
-    boost::asio::local::stream_protocol::socket host_vst_dispatch_midi_events;
-    /**
-     * The socket that forwards all `audioMaster()` calls from the Windows VST
-     * plugin to the host.
-     */
-    boost::asio::local::stream_protocol::socket vst_host_callback;
-    /**
-     * Used for both `getParameter` and `setParameter` since they mostly
-     * overlap.
-     */
-    boost::asio::local::stream_protocol::socket host_vst_parameters;
-    boost::asio::local::stream_protocol::socket host_vst_process_replacing;
-
-    /**
-     * A control socket that sends data that is not suitable for the other
-     * sockets. At the moment this is only used to, on startup, send the Windows
-     * VST plugin's `AEffect` object to the native VST plugin, and to then send
-     * the configuration (from `config`) back to the Wine host.
-     */
-    boost::asio::local::stream_protocol::socket host_vst_control;
+    Sockets<std::jthread> sockets;
 
     /**
      * The thread that handles host callbacks.
@@ -169,16 +132,10 @@ class PluginBridge {
     std::jthread host_callback_handler;
 
     /**
-     * A binary semaphore to prevent race conditions from the dispatch function
-     * being called by two threads at once. See `send_event()` for more
-     * information.
-     */
-    std::mutex dispatch_mutex;
-    std::mutex dispatch_midi_events_mutex;
-    /**
-     * A similar semaphore as the `dispatch_*` semaphores in the rare case that
-     * `getParameter()` and `setParameter()` are being called at the same time
-     * since they use the same socket.
+     * A mutex to prevent multiple simultaneous calls to `getParameter()` and
+     * `setParameter()`. This likely won't happen, but better safe than sorry.
+     * For `dispatch()` and `audioMaster()` there's some more complex logic for
+     * this in `EventHandler`.
      */
     std::mutex parameters_mutex;
 

src/plugin/utils.cpp

@@ -22,37 +22,27 @@
 #include <boost/process/search_path.hpp>
 #include <boost/process/system.hpp>
 #include <fstream>
-#include <random>
 #include <sstream>
 
 // Generated inside of the build directory
 #include <src/common/config/config.h>
 
 #include "../common/configuration.h"
+#include "../common/utils.h"
 
 namespace bp = boost::process;
 namespace fs = boost::filesystem;
 
-/**
- * Used for generating random identifiers.
- */
-constexpr char alphanumeric_characters[] =
-    "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
-
-std::string create_logger_prefix(const fs::path& socket_path) {
-    // Use the socket filename as the logger prefix, but strip the `yabridge-`
-    // part since that's redundant
-    std::string socket_name =
-        socket_path.filename().replace_extension().string();
+std::string create_logger_prefix(const fs::path& endpoint_base_dir) {
+    // Use the name of the base directory used for our sockets as the logger
+    // prefix, but strip the `yabridge-` part since that's redundant
+    std::string endpoint_name = endpoint_base_dir.filename().string();
 
     constexpr std::string_view socket_prefix("yabridge-");
-    assert(socket_name.starts_with(socket_prefix));
-    socket_name = socket_name.substr(socket_prefix.size());
+    assert(endpoint_name.starts_with(socket_prefix));
+    endpoint_name = endpoint_name.substr(socket_prefix.size());
 
-    std::ostringstream prefix;
-    prefix << "[" << socket_name << "] ";
-
-    return prefix.str();
+    return "[" + endpoint_name + "] ";
 }
 
 std::optional<fs::path> find_wineprefix() {
@@ -183,39 +173,7 @@ boost::filesystem::path generate_group_endpoint(
     }
     socket_name << ".sock";
 
-    return fs::temp_directory_path() / socket_name.str();
-}
-
-fs::path generate_plugin_endpoint() {
-    const auto plugin_name =
-        find_vst_plugin().filename().replace_extension("").string();
-
-    std::random_device random_device;
-    std::mt19937 rng(random_device());
-    fs::path candidate_endpoint;
-    do {
-        std::string random_id;
-        std::sample(
-            alphanumeric_characters,
-            alphanumeric_characters + strlen(alphanumeric_characters) - 1,
-            std::back_inserter(random_id), 8, rng);
-
-        // We'll get rid of the file descriptors immediately after accepting the
-        // sockets, so putting them inside of a subdirectory would only leave
-        // behind an empty directory
-        std::ostringstream socket_name;
-        socket_name << "yabridge-" << plugin_name << "-" << random_id
-                    << ".sock";
-
-        candidate_endpoint = fs::temp_directory_path() / socket_name.str();
-    } while (fs::exists(candidate_endpoint));
-
-    // TODO: Should probably try creating the endpoint right here and catch any
-    //       exceptions since this could technically result in a race condition
-    //       when two instances of yabridge decide to use the same endpoint name
-    //       at the same time
-
-    return candidate_endpoint;
+    return get_temporary_directory() / socket_name.str();
 }
 
 fs::path get_this_file_location() {
@@ -243,7 +201,7 @@ std::string get_wine_version() {
 
     bp::environment env = boost::this_process::environment();
     if (!env["WINELOADER"].empty()) {
-        wine_command = env.get("WINELOADER");
+        wine_command = env["WINELOADER"].to_string();
     }
 
     bp::ipstream output;
@@ -271,13 +229,13 @@ std::string get_wine_version() {
 
 std::string join_quoted_strings(std::vector<std::string>& strings) {
     bool is_first = true;
-    std::ostringstream joined_strigns{};
+    std::ostringstream joined_strings{};
     for (const auto& option : strings) {
-        joined_strigns << (is_first ? "'" : ", '") << option << "'";
+        joined_strings << (is_first ? "'" : ", '") << option << "'";
         is_first = false;
     }
 
-    return joined_strigns.str();
+    return joined_strings.str();
 }
 
 Configuration load_config_for(const fs::path& yabridge_path) {

src/plugin/utils.h

@@ -46,15 +46,17 @@ class patched_async_pipe : public boost::process::async_pipe {
 enum class PluginArchitecture { vst_32, vst_64 };
 
 /**
- * Create a logger prefix based on the unique socket path for easy
- * identification. The socket path contains both the plugin's name and a unique
- * identifier.
+ * Create a logger prefix based on the endpoint base directory used for the
+ * sockets for easy identification. This will result in a prefix of the form
+ * `[<plugin_name>-<random_id>] `.
  *
- * @param socket_path The path to the socket endpoint in use.
+ * @param endpoint_base_dir A directory name generated by
+ *   `generate_endpoint_base()`.
  *
  * @return A prefix string for log messages.
  */
-std::string create_logger_prefix(const boost::filesystem::path& socket_path);
+std::string create_logger_prefix(
+    const boost::filesystem::path& endpoint_base_dir);
 
 /**
  * Determine the architecture of a VST plugin (or rather, a .dll file) based on
@@ -117,10 +119,11 @@ std::optional<boost::filesystem::path> find_wineprefix();
 /**
  * Generate the group socket endpoint name used based on the name of the group,
  * the Wine prefix in use and the plugin architecture. The resulting format is
- * `/tmp/yabridge-group-<group_name>-<wine_prefix_id>-<architecture>.sock`. In
- * this socket name the `wine_prefix_id` is a numerical hash based on the Wine
- * prefix in use. This way the same group name can be used for multiple Wine
- * prefixes and for both 32 and 64 bit plugins without clashes.
+ * in the form
+ * `/run/user/<uid>/yabridge-group-<group_name>-<wine_prefix_id>-<architecture>.sock`.
+ * In this socket name the `wine_prefix_id` is a numerical hash based on the
+ * Wine prefix in use. This way the same group name can be used for multiple
+ * Wine prefixes and for both 32 and 64 bit plugins without clashes.
  *
  * @param group_name The name of the plugin group.
  * @param wine_prefix The name of the Wine prefix in use. This should be
@@ -140,16 +143,6 @@ boost::filesystem::path generate_group_endpoint(
     const boost::filesystem::path& wine_prefix,
     const PluginArchitecture architecture);
 
-/**
- * Generate a unique name for the Unix domain socket endpoint based on the VST
- * plugin's name. This will also generate the parent directory if it does not
- * yet exist since we're using this in the constructor's initializer list.
- *
- * @return A path to a not yet existing Unix domain socket endpoint.
- * @throw std::runtime_error If no matching .dll file could be found.
- */
-boost::filesystem::path generate_plugin_endpoint();
-
 /**
  * Return a path to this `.so` file. This can be used to find out from where
  * this link to or copy of `libyabridge.so` was loaded.

src/wine-host/bridges/group.cpp

@@ -29,11 +29,6 @@ namespace fs = boost::filesystem;
 
 using namespace std::literals::chrono_literals;
 
-/**
- * The delay between calls to the event loop at a more than cinematic 30 fps.
- */
-constexpr std::chrono::duration event_loop_interval = 1000ms / 30;
-
 /**
  * Listen on the specified endpoint if no process is already listening there,
  * otherwise throw. This is needed to handle these three situations:
@@ -89,37 +84,40 @@ StdIoCapture::~StdIoCapture() {
 GroupBridge::GroupBridge(boost::filesystem::path group_socket_path)
     : logger(Logger::create_from_environment(
           create_logger_prefix(group_socket_path))),
-      plugin_context(),
+      main_context(),
       stdio_context(),
       stdout_redirect(stdio_context, STDOUT_FILENO),
       stderr_redirect(stdio_context, STDERR_FILENO),
       group_socket_endpoint(group_socket_path.string()),
-      group_socket_acceptor(
-          create_acceptor_if_inactive(plugin_context, group_socket_endpoint)),
-      events_timer(plugin_context),
-      shutdown_timer(plugin_context) {
+      group_socket_acceptor(create_acceptor_if_inactive(main_context.context,
+                                                        group_socket_endpoint)),
+      shutdown_timer(main_context.context) {
     // Write this process's original STDOUT and STDERR streams to the logger
     // TODO: This works for output generated by plugins, but not for debug
     //       messages generated by wineserver. Is it possible to catch those?
     async_log_pipe_lines(stdout_redirect.pipe, stdout_buffer, "[STDOUT] ");
     async_log_pipe_lines(stderr_redirect.pipe, stderr_buffer, "[STDERR] ");
 
-    stdio_handler = std::jthread([&]() { stdio_context.run(); });
+    stdio_handler = Win32Thread([&]() { stdio_context.run(); });
 }
 
 GroupBridge::~GroupBridge() {
     stdio_context.stop();
 }
 
-void GroupBridge::handle_plugin_dispatch(const GroupRequest request) {
+void GroupBridge::handle_plugin_dispatch(size_t plugin_id) {
     // At this point the `active_plugins` map will already contain the
     // intialized plugin's `Vst2Bridge` instance and this thread's handle
-    auto& [thread, bridge] = active_plugins.at(request);
+    Vst2Bridge* bridge;
+    {
+        std::lock_guard lock(active_plugins_mutex);
+        bridge = active_plugins[plugin_id].second.get();
+    }
 
     // Blocks this thread until the plugin shuts down, handling all events on
     // the main IO context
     bridge->handle_dispatch();
-    logger.log("'" + request.plugin_path + "' has exited");
+    logger.log("'" + bridge->vst_plugin_path.string() + "' has exited");
 
     // After the plugin has exited we'll remove this thread's plugin from the
     // active plugins. This is done within the IO context because the call to
@@ -127,11 +125,12 @@ void GroupBridge::handle_plugin_dispatch(const GroupRequest request) {
     // potentially corrupt our heap. This way we can also properly join the
     // thread again. If no active plugins remain, then we'll terminate the
     // process.
-    boost::asio::post(plugin_context, [&, request]() {
+    boost::asio::post(main_context.context, [this, plugin_id]() {
         std::lock_guard lock(active_plugins_mutex);
 
-        // The join is implicit because we're using std::jthread
-        active_plugins.erase(request);
+        // The join is implicit because we're using Win32Thread (which mimics
+        // std::jthread)
+        active_plugins.erase(plugin_id);
     });
 
     // Defer actually shutting down the process to allow for fast plugin
@@ -148,7 +147,7 @@ void GroupBridge::handle_plugin_dispatch(const GroupRequest request) {
         if (active_plugins.size() == 0) {
             logger.log(
                 "All plugins have exited, shutting down the group process");
-            plugin_context.stop();
+            main_context.stop();
         }
     });
 }
@@ -159,7 +158,7 @@ void GroupBridge::handle_incoming_connections() {
 
     logger.log(
         "Group host is up and running, now accepting incoming connections");
-    plugin_context.run();
+    main_context.run();
 }
 
 bool GroupBridge::should_skip_message_loop() {
@@ -189,7 +188,7 @@ void GroupBridge::accept_requests() {
                 logger.log("Error while listening for incoming connections:");
                 logger.log(error.message());
 
-                plugin_context.stop();
+                main_context.stop();
             }
 
             // Read the parameters, and then host the plugin in this process
@@ -201,27 +200,28 @@ void GroupBridge::accept_requests() {
             const auto request = read_object<GroupRequest>(socket);
             write_object(socket, GroupResponse{boost::this_process::get_id()});
 
-            // Collisions in the generated socket names should be very rare, but
-            // it could in theory happen
-            assert(!active_plugins.contains(request));
-
             // The plugin has to be initiated on the IO context's thread because
             // this has to be done on the same thread that's handling messages,
             // and all window messages have to be handled from the same thread.
             logger.log("Received request to host '" + request.plugin_path +
-                       "' using socket '" + request.socket_path + "'");
+                       "' using socket endpoint base directory '" +
+                       request.endpoint_base_dir + "'");
             try {
                 auto bridge = std::make_unique<Vst2Bridge>(
-                    plugin_context, request.plugin_path, request.socket_path);
+                    main_context, request.plugin_path,
+                    request.endpoint_base_dir);
                 logger.log("Finished initializing '" + request.plugin_path +
                            "'");
 
                 // Start listening for dispatcher events sent to the plugin's
                 // socket on another thread. The actual event handling will
-                // still occur within this IO context.
-                active_plugins[request] =
-                    std::pair(std::jthread([&, request]() {
-                                  handle_plugin_dispatch(request);
+                // still be posted to this IO context so that every plugin's
+                // primary event handling happens on the main thread. Since this
+                // is only used within this context we don't need any locks.
+                const size_t plugin_id = next_plugin_id.fetch_add(1);
+                active_plugins[plugin_id] =
+                    std::pair(Win32Thread([this, plugin_id]() {
+                                  handle_plugin_dispatch(plugin_id);
                               }),
                               std::move(bridge));
             } catch (const std::runtime_error& error) {
@@ -235,16 +235,7 @@ void GroupBridge::accept_requests() {
 }
 
 void GroupBridge::async_handle_events() {
-    // Try to keep a steady framerate, but add in delays to let other events get
-    // handled if the GUI message handling somehow takes very long.
-    events_timer.expires_at(
-        std::max(events_timer.expiry() + event_loop_interval,
-                 std::chrono::steady_clock::now() + 5ms));
-    events_timer.async_wait([&](const boost::system::error_code& error) {
-        if (error.failed()) {
-            return;
-        }
-
+    main_context.async_handle_events([&]() {
         {
             // Always handle X11 events
             std::lock_guard lock(active_plugins_mutex);
@@ -274,8 +265,6 @@ void GroupBridge::async_handle_events() {
                 DispatchMessage(&msg);
             }
         }
-
-        async_handle_events();
     });
 }
 

src/wine-host/bridges/group.h

@@ -22,6 +22,7 @@
 #include <boost/asio/streambuf.hpp>
 #include <boost/filesystem.hpp>
 
+#include <atomic>
 #include <thread>
 
 #include "vst2.h"
@@ -132,21 +133,21 @@ class GroupBridge {
      * `accept_requests` since it has to be initiated inside of the IO context's
      * thread.
      *
-     * Once the plugin has exited, this thread will then remove itself from the
-     * `active_plugins` map. If this causes the vector to become empty, we will
-     * terminate this process. This check will be delayed by a few seconds to
-     * prevent having to constantly restart the group process during plugin
-     * scanning.
+     * Once the plugin has exited, this thread will then be joined to the main
+     * thread and removed from the `active_plugins` from the main IO context. If
+     * this causes the vector to become empty, we will terminate this process.
+     * This check is delayed by a few seconds to prevent having to constantly
+     * restart the group process during plugin scanning.
      *
-     * @param request Information about the plugin to launch, i.e. the path to
-     *   the plugin and the path of the socket endpoint that will be used for
-     *   communication.
+     * @param plugin_id The ID of this plugin in the `active_plugins` map. The
+     *   thread can fetch the plugin's `Vst2Bridge` instance from that map using
+     *   this identifier.
      *
      * @note In the case that the process starts but no plugin gets initiated,
      *   then the process will never exit on its own. This should not happen
      *   though.
      */
-    void handle_plugin_dispatch(const GroupRequest request);
+    void handle_plugin_dispatch(size_t plugin_id);
 
     /**
      * Listen for new requests to spawn plugins within this process and handle
@@ -178,7 +179,7 @@ class GroupBridge {
      * event handling and message loop interaction also has to be done from that
      * thread, which is why we initialize the plugin here and use the
      * `handle_dispatch()` function to run events within the same
-     * `plugin_context`.
+     * `main_context`.
      *
      * @see handle_plugin_dispatch
      */
@@ -216,13 +217,13 @@ class GroupBridge {
      * operations that may involve the Win32 mesasge loop (e.g. initialization
      * and most `AEffect::dispatcher()` calls) should be run on.
      */
-    boost::asio::io_context plugin_context;
+    MainContext main_context;
     /**
      * A seperate IO context that handles the STDIO redirect through
-     * `StdIoCapture`. This is seperated the `plugin_context` above so that
-     * STDIO capture does not get blocked by blocking GUI operations. Since
-     * every GUI related operation should be run from the same thread, we can't
-     * just add another thread to the main IO context.
+     * `StdIoCapture`. This is separated from the `main_context` above so that
+     * STDIO capture does not get blocked by GUI operations. Since every GUI
+     * related operation should be run from the same thread, we can't just add
+     * another thread to the main IO context.
      */
     boost::asio::io_context stdio_context;
 
@@ -243,7 +244,7 @@ class GroupBridge {
     /**
      * A thread that runs the `stdio_context` loop.
      */
-    std::jthread stdio_handler;
+    Win32Thread stdio_handler;
 
     boost::asio::local::stream_protocol::endpoint group_socket_endpoint;
     /**
@@ -257,11 +258,19 @@ class GroupBridge {
      * along with their plugin instance. After a plugin has exited or its
      * initialization has failed, the thread handling it will remove itself from
      * this map. This is to keep track of the amount of plugins currently
-     * running with their associated thread handles.
+     * running with their associated thread handles. The key that identifies the
+     * thread and plugin is a unique plugin ID obtained by doing a fetch-and-add
+     * on `next_plugin_id`.
      */
-    std::unordered_map<GroupRequest,
-                       std::pair<std::jthread, std::unique_ptr<Vst2Bridge>>>
+    std::unordered_map<size_t,
+                       std::pair<Win32Thread, std::unique_ptr<Vst2Bridge>>>
         active_plugins;
+    /**
+     * A counter for the next unique plugin ID. When hosting a new plugin we'll
+     * do a fetch-and-add to ensure that every thread gets its own unique
+     * identifier.
+     */
+    std::atomic_size_t next_plugin_id;
     /**
      * A mutex to prevent two threads from simultaneously accessing the plugins
      * map, and also to prevent `handle_plugin_dispatch()` from terminating the
@@ -270,14 +279,6 @@ class GroupBridge {
      */
     std::mutex active_plugins_mutex;
 
-    /**
-     * A timer used to repeatedly handle the Win32 message loop and the X11
-     * events.
-     *
-     8 @see async_handle_events
-     */
-    boost::asio::steady_timer events_timer;
-
     /**
      * A timer to defer shutting down the process, allowing for fast plugin
      * scanning without having to start a new group host process for each

src/wine-host/bridges/vst2.cpp

@@ -19,9 +19,9 @@
 #include <boost/asio/dispatch.hpp>
 #include <future>
 #include <iostream>
+#include <set>
 
 #include "../../common/communication.h"
-#include "../../common/events.h"
 
 /**
  * A function pointer to what should be the entry point of a VST plugin.
@@ -39,16 +39,17 @@ Vst2Bridge* current_bridge_instance = nullptr;
  */
 std::mutex current_bridge_instance_mutex;
 
+/**
+ * Opcodes that should always be handled on the main thread because they may
+ * involve GUI operations.
+ */
+const std::set<int> unsafe_opcodes{effOpen,     effClose,     effEditGetRect,
+                                   effEditOpen, effEditClose, effEditIdle,
+                                   effEditTop};
+
 intptr_t VST_CALL_CONV
 host_callback_proxy(AEffect*, int, int, intptr_t, void*, float);
 
-// We need to use the `CreateThread` WinAPI functions instead of `std::thread`
-// to use the correct calling conventions within threads. Otherwise we'll get
-// some rare and impossible to debug data races in some particular plugins.
-uint32_t WINAPI handle_dispatch_midi_events_proxy(void*);
-uint32_t WINAPI handle_parameters_proxy(void*);
-uint32_t WINAPI handle_process_replacing_proxy(void*);
-
 /**
  * Fetch the Vst2Bridge instance stored in one of the two pointers reserved
  * for the host of the hosted VST plugin. This is sadly needed as a workaround
@@ -65,18 +66,13 @@ Vst2Bridge& get_bridge_instance(const AEffect* plugin) {
     return *static_cast<Vst2Bridge*>(plugin->ptr1);
 }
 
-Vst2Bridge::Vst2Bridge(boost::asio::io_context& main_context,
+Vst2Bridge::Vst2Bridge(MainContext& main_context,
                        std::string plugin_dll_path,
-                       std::string socket_endpoint_path)
-    : io_context(main_context),
+                       std::string endpoint_base_dir)
+    : vst_plugin_path(plugin_dll_path),
+      main_context(main_context),
       plugin_handle(LoadLibrary(plugin_dll_path.c_str()), FreeLibrary),
-      socket_endpoint(socket_endpoint_path),
-      host_vst_dispatch(io_context),
-      host_vst_dispatch_midi_events(io_context),
-      vst_host_callback(io_context),
-      host_vst_parameters(io_context),
-      host_vst_process_replacing(io_context),
-      host_vst_control(io_context) {
+      sockets(main_context.context, endpoint_base_dir, false) {
     // Got to love these C APIs
     if (!plugin_handle) {
         throw std::runtime_error("Could not load the Windows .dll file at '" +
@@ -101,14 +97,7 @@ Vst2Bridge::Vst2Bridge(boost::asio::io_context& main_context,
             "'.");
     }
 
-    // It's very important that these sockets are accepted to in the same order
-    // in the Linux plugin
-    host_vst_dispatch.connect(socket_endpoint);
-    host_vst_dispatch_midi_events.connect(socket_endpoint);
-    vst_host_callback.connect(socket_endpoint);
-    host_vst_parameters.connect(socket_endpoint);
-    host_vst_process_replacing.connect(socket_endpoint);
-    host_vst_control.connect(socket_endpoint);
+    sockets.connect();
 
     // Initialize after communication has been set up
     // We'll try to do the same `get_bridge_isntance` trick as in
@@ -132,24 +121,212 @@ Vst2Bridge::Vst2Bridge(boost::asio::io_context& main_context,
     // of this object will be sent over the `dispatcher()` socket. This would be
     // done after the host calls `effOpen()`, and when the plugin calls
     // `audioMasterIOChanged()`.
-    write_object(host_vst_control, EventResult{.return_value = 0,
-                                               .payload = *plugin,
-                                               .value_payload = std::nullopt});
+    write_object(sockets.host_vst_control,
+                 EventResult{.return_value = 0,
+                             .payload = *plugin,
+                             .value_payload = std::nullopt});
 
     // After sending the AEffect struct we'll receive this instance's
     // configuration as a response
-    config = read_object<Configuration>(host_vst_control);
+    config = read_object<Configuration>(sockets.host_vst_control);
 
     // This works functionally identically to the `handle_dispatch()` function,
     // but this socket will only handle MIDI events and it will handle them
     // eagerly. This is needed because of Win32 API limitations.
-    dispatch_midi_events_handler =
-        Win32Thread(handle_dispatch_midi_events_proxy, this);
+    dispatch_midi_events_handler = Win32Thread([&]() {
+        sockets.host_vst_dispatch_midi_events.receive(
+            std::nullopt, [&](Event& event, bool /*on_main_thread*/) {
+                if (BOOST_LIKELY(event.opcode == effProcessEvents)) {
+                    // For 99% of the plugins we can just call
+                    // `effProcessReplacing()` and be done with it, but a select
+                    // few plugins (I could only find Kontakt that does this)
+                    // don't actually make copies of the events they receive and
+                    // only store pointers, meaning that they have to live at
+                    // least until the next audio buffer gets processed. We're
+                    // not using `passthrough_events()` here directly because we
+                    // need to store a copy of the `DynamicVstEvents` struct
+                    // before passing the generated `VstEvents` object to the
+                    // plugin.
+                    std::lock_guard lock(next_buffer_midi_events_mutex);
 
-    parameters_handler = Win32Thread(handle_parameters_proxy, this);
+                    next_audio_buffer_midi_events.push_back(
+                        std::get<DynamicVstEvents>(event.payload));
+                    DynamicVstEvents& events =
+                        next_audio_buffer_midi_events.back();
 
-    process_replacing_handler =
-        Win32Thread(handle_process_replacing_proxy, this);
+                    // Exact same handling as in `passthrough_event`, apart from
+                    // making a copy of the events first
+                    const intptr_t return_value = plugin->dispatcher(
+                        plugin, event.opcode, event.index, event.value,
+                        &events.as_c_events(), event.option);
+
+                    EventResult response{.return_value = return_value,
+                                         .payload = nullptr,
+                                         .value_payload = std::nullopt};
+
+                    return response;
+                } else {
+                    using namespace std::placeholders;
+
+                    std::cerr << "[Warning] Received non-MIDI "
+                                 "event on MIDI processing thread"
+                              << std::endl;
+
+                    // Maybe this should just be a hard error instead, since it
+                    // should never happen
+                    return passthrough_event(
+                        plugin, std::bind(&Vst2Bridge::dispatch_wrapper, this,
+                                          _1, _2, _3, _4, _5, _6))(event);
+                }
+            });
+    });
+
+    parameters_handler = Win32Thread([&]() {
+        while (true) {
+            try {
+                // Both `getParameter` and `setParameter` functions are passed
+                // through on this socket since they have a lot of overlap. The
+                // presence of the `value` field tells us which one we're
+                // dealing with.
+                auto request =
+                    read_object<Parameter>(sockets.host_vst_parameters);
+                if (request.value) {
+                    // `setParameter`
+                    plugin->setParameter(plugin, request.index, *request.value);
+
+                    ParameterResult response{std::nullopt};
+                    write_object(sockets.host_vst_parameters, response);
+                } else {
+                    // `getParameter`
+                    float value = plugin->getParameter(plugin, request.index);
+
+                    ParameterResult response{value};
+                    write_object(sockets.host_vst_parameters, response);
+                }
+            } catch (const boost::system::system_error&) {
+                // The plugin has cut off communications, so we can shut down
+                // this host application
+                break;
+            }
+        }
+    });
+
+    process_replacing_handler = Win32Thread([&]() {
+        // These are used as scratch buffers to prevent unnecessary allocations.
+        // Since don't know in advance whether the host will call
+        // `processReplacing` or `processDoubleReplacing` we'll just create
+        // both.
+        std::vector<std::vector<float>> output_buffers_single_precision(
+            plugin->numOutputs);
+        std::vector<std::vector<double>> output_buffers_double_precision(
+            plugin->numOutputs);
+
+        while (true) {
+            try {
+                auto request = read_object<AudioBuffers>(
+                    sockets.host_vst_process_replacing, process_buffer);
+                // Let the plugin process the MIDI events that were received
+                // since the last buffer, and then clean up those events. This
+                // approach should not be needed but Kontakt only stores
+                // pointers to rather than copies of the events.
+                std::lock_guard lock(next_buffer_midi_events_mutex);
+
+                // Since the host should only be calling one of `process()`,
+                // processReplacing()` or `processDoubleReplacing()`, we can all
+                // handle them over the same socket. We pick which one to call
+                // depending on the type of data we got sent and the plugin's
+                // reported support for these functions.
+                std::visit(
+                    overload{
+                        [&](std::vector<std::vector<float>>& input_buffers) {
+                            // The process functions expect a `float**` for
+                            // their inputs and their outputs
+                            std::vector<float*> inputs;
+                            for (auto& buffer : input_buffers) {
+                                inputs.push_back(buffer.data());
+                            }
+
+                            // We reuse the buffers to avoid some unnecessary
+                            // heap allocations, so we need to make sure the
+                            // buffers are large enough since plugins can change
+                            // their output configuration. The type we're using
+                            // here (single precision floats vs double
+                            // precisioon doubles) should be the same as the one
+                            // we're sending in our response.
+                            std::vector<float*> outputs;
+                            output_buffers_single_precision.resize(
+                                plugin->numOutputs);
+                            for (auto& buffer :
+                                 output_buffers_single_precision) {
+                                buffer.resize(request.sample_frames);
+                                outputs.push_back(buffer.data());
+                            }
+
+                            // Any plugin made in the last fifteen years or so
+                            // should support `processReplacing`. In the off
+                            // chance it does not we can just emulate this
+                            // behavior ourselves.
+                            if (plugin->processReplacing) {
+                                plugin->processReplacing(plugin, inputs.data(),
+                                                         outputs.data(),
+                                                         request.sample_frames);
+                            } else {
+                                // If we zero out this buffer then the behavior
+                                // is the same as `processReplacing``
+                                for (std::vector<float>& buffer :
+                                     output_buffers_single_precision) {
+                                    std::fill(buffer.begin(), buffer.end(),
+                                              0.0);
+                                }
+
+                                plugin->process(plugin, inputs.data(),
+                                                outputs.data(),
+                                                request.sample_frames);
+                            }
+
+                            AudioBuffers response{
+                                output_buffers_single_precision,
+                                request.sample_frames};
+                            write_object(sockets.host_vst_process_replacing,
+                                         response, process_buffer);
+                        },
+                        [&](std::vector<std::vector<double>>& input_buffers) {
+                            // Exactly the same as the above, but for double
+                            // precision audio
+                            std::vector<double*> inputs;
+                            for (auto& buffer : input_buffers) {
+                                inputs.push_back(buffer.data());
+                            }
+
+                            std::vector<double*> outputs;
+                            output_buffers_double_precision.resize(
+                                plugin->numOutputs);
+                            for (auto& buffer :
+                                 output_buffers_double_precision) {
+                                buffer.resize(request.sample_frames);
+                                outputs.push_back(buffer.data());
+                            }
+
+                            plugin->processDoubleReplacing(
+                                plugin, inputs.data(), outputs.data(),
+                                request.sample_frames);
+
+                            AudioBuffers response{
+                                output_buffers_double_precision,
+                                request.sample_frames};
+                            write_object(sockets.host_vst_process_replacing,
+                                         response, process_buffer);
+                        }},
+                    request.buffers);
+
+                next_audio_buffer_midi_events.clear();
+            } catch (const boost::system::system_error&) {
+                // The plugin has cut off communications, so we can shut down
+                // this host application
+                break;
+            }
+        }
+    });
 }
 
 bool Vst2Bridge::should_skip_message_loop() const {
@@ -157,234 +334,36 @@ bool Vst2Bridge::should_skip_message_loop() const {
 }
 
 void Vst2Bridge::handle_dispatch() {
-    while (true) {
-        try {
-            receive_event(
-                host_vst_dispatch, std::nullopt,
-                passthrough_event(
-                    plugin,
-                    [&](AEffect* plugin, int opcode, int index, intptr_t value,
-                        void* data, float option) -> intptr_t {
-                        // Instead of running `plugin->dispatcher()` (or
-                        // `dispatch_wrapper()`) directly, we'll run the
-                        // function within the IO context so all events will be
-                        // executed on the same thread as the one that runs the
-                        // Win32 message loop
+    sockets.host_vst_dispatch.receive(
+        std::nullopt, [&](Event& event, bool /*on_main_thread*/) {
+            // TODO: As per the TODO in `passthrough_event`, this can use a
+            //       round of refactoring now that we never use its returned
+            //       lambda directly anymore
+            return passthrough_event(
+                plugin,
+                [&](AEffect* plugin, int opcode, int index, intptr_t value,
+                    void* data, float option) -> intptr_t {
+                    // Certain functions will most definitely involve the GUI or
+                    // the Win32 message loop. These functions have to be
+                    // performed on the thread that is running the IO context,
+                    // since this is also where the plugins were instantiated
+                    // and where the Win32 message loop is handled.
+                    if (unsafe_opcodes.contains(opcode)) {
                         std::promise<intptr_t> dispatch_result;
-                        boost::asio::dispatch(io_context, [&]() {
+                        boost::asio::dispatch(main_context.context, [&]() {
                             const intptr_t result = dispatch_wrapper(
                                 plugin, opcode, index, value, data, option);
 
                             dispatch_result.set_value(result);
                         });
 
-                        // The message loop and X11 event handling will be run
-                        // separately on a timer
                         return dispatch_result.get_future().get();
-                    }));
-        } catch (const boost::system::system_error&) {
-            // The plugin has cut off communications, so we can shut down this
-            // host application
-            break;
-        }
-    }
-}
-
-void Vst2Bridge::handle_dispatch_midi_events() {
-    while (true) {
-        try {
-            receive_event(
-                host_vst_dispatch_midi_events, std::nullopt, [&](Event& event) {
-                    if (BOOST_LIKELY(event.opcode == effProcessEvents)) {
-                        // For 99% of the plugins we can just call
-                        // `effProcessReplacing()` and be done with it, but a
-                        // select few plugins (I could only find Kontakt that
-                        // does this) don't actually make copies of the events
-                        // they receive and only store pointers, meaning that
-                        // they have to live at least until the next audio
-                        // buffer gets processed. We're not using
-                        // `passhtourhg_events()` here directly because we need
-                        // to store a copy of the `DynamicVstEvents` struct
-                        // before passing the generated `VstEvents` object to
-                        // the plugin.
-                        std::lock_guard lock(next_buffer_midi_events_mutex);
-
-                        next_audio_buffer_midi_events.push_back(
-                            std::get<DynamicVstEvents>(event.payload));
-                        DynamicVstEvents& events =
-                            next_audio_buffer_midi_events.back();
-
-                        // Exact same handling as in `passthrough_event`, apart
-                        // from making a copy of the events first
-                        const intptr_t return_value = plugin->dispatcher(
-                            plugin, event.opcode, event.index, event.value,
-                            &events.as_c_events(), event.option);
-
-                        EventResult response{.return_value = return_value,
-                                             .payload = nullptr,
-                                             .value_payload = std::nullopt};
-
-                        return response;
                     } else {
-                        using namespace std::placeholders;
-
-                        std::cerr << "[Warning] Received non-MIDI "
-                                     "event on MIDI processing thread"
-                                  << std::endl;
-
-                        // Maybe this should just be a hard error instead, since
-                        // it should never happen
-                        return passthrough_event(
-                            plugin,
-                            std::bind(&Vst2Bridge::dispatch_wrapper, this, _1,
-                                      _2, _3, _4, _5, _6))(event);
+                        return dispatch_wrapper(plugin, opcode, index, value,
+                                                data, option);
                     }
-                });
-        } catch (const boost::system::system_error&) {
-            // The plugin has cut off communications, so we can shut down this
-            // host application
-            break;
-        }
-    }
-}
-
-void Vst2Bridge::handle_parameters() {
-    while (true) {
-        try {
-            // Both `getParameter` and `setParameter` functions are passed
-            // through on this socket since they have a lot of overlap. The
-            // presence of the `value` field tells us which one we're dealing
-            // with.
-            auto request = read_object<Parameter>(host_vst_parameters);
-            if (request.value) {
-                // `setParameter`
-                plugin->setParameter(plugin, request.index, *request.value);
-
-                ParameterResult response{std::nullopt};
-                write_object(host_vst_parameters, response);
-            } else {
-                // `getParameter`
-                float value = plugin->getParameter(plugin, request.index);
-
-                ParameterResult response{value};
-                write_object(host_vst_parameters, response);
-            }
-        } catch (const boost::system::system_error&) {
-            // The plugin has cut off communications, so we can shut down this
-            // host application
-            break;
-        }
-    }
-}
-
-void Vst2Bridge::handle_process_replacing() {
-    // These are used as scratch buffers to prevent unnecessary allocations.
-    // Since don't know in advance whether the host will call `processReplacing`
-    // or `processDoubleReplacing` we'll just create both.
-    std::vector<std::vector<float>> output_buffers_single_precision(
-        plugin->numOutputs);
-    std::vector<std::vector<double>> output_buffers_double_precision(
-        plugin->numOutputs);
-
-    while (true) {
-        try {
-            auto request = read_object<AudioBuffers>(host_vst_process_replacing,
-                                                     process_buffer);
-            // Let the plugin process the MIDI events that were received since
-            // the last buffer, and then clean up those events. This approach
-            // should not be needed but Kontakt only stores pointers to rather
-            // than copies of the events.
-            std::lock_guard lock(next_buffer_midi_events_mutex);
-
-            // Since the host should only be calling one of `process()`,
-            // processReplacing()` or `processDoubleReplacing()`, we can all
-            // handle them over the same socket. We pick which one to call
-            // depending on the type of data we got sent and the plugin's
-            // reported support for these functions.
-            std::visit(
-                overload{
-                    [&](std::vector<std::vector<float>>& input_buffers) {
-                        // The process functions expect a `float**` for their
-                        // inputs and their outputs
-                        std::vector<float*> inputs;
-                        for (auto& buffer : input_buffers) {
-                            inputs.push_back(buffer.data());
-                        }
-
-                        // We reuse the buffers to avoid some unnecessary heap
-                        // allocations, so we need to make sure the buffers are
-                        // large enough since plugins can change their output
-                        // configuration. The type we're using here (single
-                        // precision floats vs double precisioon doubles) should
-                        // be the same as the one we're sending in our response.
-                        std::vector<float*> outputs;
-                        output_buffers_single_precision.resize(
-                            plugin->numOutputs);
-                        for (auto& buffer : output_buffers_single_precision) {
-                            buffer.resize(request.sample_frames);
-                            outputs.push_back(buffer.data());
-                        }
-
-                        // Any plugin made in the last fifteen years or so
-                        // should support `processReplacing`. In the off chance
-                        // it does not we can just emulate this behavior
-                        // ourselves.
-                        if (plugin->processReplacing) {
-                            plugin->processReplacing(plugin, inputs.data(),
-                                                     outputs.data(),
-                                                     request.sample_frames);
-                        } else {
-                            // If we zero out this buffer then the behavior is
-                            // the same as `processReplacing``
-                            for (std::vector<float>& buffer :
-                                 output_buffers_single_precision) {
-                                std::fill(buffer.begin(), buffer.end(), 0.0);
-                            }
-
-                            plugin->process(plugin, inputs.data(),
-                                            outputs.data(),
-                                            request.sample_frames);
-                        }
-
-                        AudioBuffers response{output_buffers_single_precision,
-                                              request.sample_frames};
-                        write_object(host_vst_process_replacing, response,
-                                     process_buffer);
-                    },
-                    [&](std::vector<std::vector<double>>& input_buffers) {
-                        // Exactly the same as the above, but for double
-                        // precision audio
-                        std::vector<double*> inputs;
-                        for (auto& buffer : input_buffers) {
-                            inputs.push_back(buffer.data());
-                        }
-
-                        std::vector<double*> outputs;
-                        output_buffers_double_precision.resize(
-                            plugin->numOutputs);
-                        for (auto& buffer : output_buffers_double_precision) {
-                            buffer.resize(request.sample_frames);
-                            outputs.push_back(buffer.data());
-                        }
-
-                        plugin->processDoubleReplacing(plugin, inputs.data(),
-                                                       outputs.data(),
-                                                       request.sample_frames);
-
-                        AudioBuffers response{output_buffers_double_precision,
-                                              request.sample_frames};
-                        write_object(host_vst_process_replacing, response,
-                                     process_buffer);
-                    }},
-                request.buffers);
-
-            next_audio_buffer_midi_events.clear();
-        } catch (const boost::system::system_error&) {
-            // The plugin has cut off communications, so we can shut down this
-            // host application
-            break;
-        }
-    }
+                })(event);
+        });
 }
 
 intptr_t Vst2Bridge::dispatch_wrapper(AEffect* plugin,
@@ -419,7 +398,7 @@ intptr_t Vst2Bridge::dispatch_wrapper(AEffect* plugin,
             // When hosting multiple plugins in a group process, all plugins
             // should get a unique window class
             const std::string window_class =
-                "yabridge plugin " + socket_endpoint.path();
+                "yabridge plugin " + sockets.base_dir.string();
             Editor& editor_instance = editor.emplace<Editor>(
                 config, window_class, x11_handle, plugin);
 
@@ -570,19 +549,9 @@ intptr_t Vst2Bridge::host_callback(AEffect* effect,
                                    intptr_t value,
                                    void* data,
                                    float option) {
-    // HACK: Sadly this is needed to work around a mutual recursion issue with
-    //       REAPER and Renoise. See #29 and #32.
-    // TODO: We don't have access to the verbosity level here, but it would be
-    //       nice to log that this is being skipped when `YABRIDGE_DEBUG_LEVEL
-    //       >= 2`.
-    if (config.hack_reaper_update_display &&
-        opcode == audioMasterUpdateDisplay) {
-        return 0;
-    }
-
     HostCallbackDataConverter converter(effect, time_info);
-    return send_event(vst_host_callback, host_callback_mutex, converter,
-                      std::nullopt, opcode, index, value, data, option);
+    return sockets.vst_host_callback.send(converter, std::nullopt, opcode,
+                                          index, value, data, option);
 }
 
 intptr_t VST_CALL_CONV host_callback_proxy(AEffect* effect,
@@ -594,18 +563,3 @@ intptr_t VST_CALL_CONV host_callback_proxy(AEffect* effect,
     return get_bridge_instance(effect).host_callback(effect, opcode, index,
                                                      value, data, option);
 }
-
-uint32_t WINAPI handle_dispatch_midi_events_proxy(void* instance) {
-    static_cast<Vst2Bridge*>(instance)->handle_dispatch_midi_events();
-    return 0;
-}
-
-uint32_t WINAPI handle_parameters_proxy(void* instance) {
-    static_cast<Vst2Bridge*>(instance)->handle_parameters();
-    return 0;
-}
-
-uint32_t WINAPI handle_process_replacing_proxy(void* instance) {
-    static_cast<Vst2Bridge*>(instance)->handle_process_replacing();
-    return 0;
-}

src/wine-host/bridges/vst2.h

@@ -29,6 +29,7 @@
 #include <boost/asio/local/stream_protocol.hpp>
 #include <mutex>
 
+#include "../../common/communication.h"
 #include "../../common/configuration.h"
 #include "../../common/logging.h"
 #include "../editor.h"
@@ -46,7 +47,7 @@ struct EditorOpening {};
  * plugin and provides host callback function for the plugin to talk back.
  *
  * @remark Because of Win32 API limitations, all window handling has to be done
- *   from the same thread. Most plugins won't have any issues when using
+ *   from a single thread. Most plugins won't have any issues when using
  *   multiple message loops, but the Melda plugins for instance will only update
  *   their GUIs from the message loop of the thread that created the first
  *   instance. This is why we pass an IO context to this class so everything
@@ -64,8 +65,8 @@ class Vst2Bridge {
      *   also be run from this context.
      * @param plugin_dll_path A (Unix style) path to the VST plugin .dll file to
      *   load.
-     * @param socket_endpoint_path A (Unix style) path to the Unix socket
-     *   endpoint the native VST plugin created to communicate over.
+     * @param endpoint_base_dir The base directory used for the socket
+     *   endpoints. See `Sockets` for more information.
      *
      * @note The object has to be constructed from the same thread that calls
      *   `main_context.run()`.
@@ -73,9 +74,9 @@ class Vst2Bridge {
      * @throw std::runtime_error Thrown when the VST plugin could not be loaded,
      *   or if communication could not be set up.
      */
-    Vst2Bridge(boost::asio::io_context& main_context,
+    Vst2Bridge(MainContext& main_context,
                std::string plugin_dll_path,
-               std::string socket_endpoint_path);
+               std::string endpoint_base_dir);
 
     /**
      * Returns true if the message loop should be skipped. This happens when the
@@ -127,14 +128,6 @@ class Vst2Bridge {
      */
     void handle_win32_events();
 
-    // These functions are the entry points for the `*_handler` threads
-    // defined below. They're defined here because we can't use lambdas with
-    // WinAPI's `CreateThread` which is needed to support the proper call
-    // conventions the VST plugins expect.
-    void handle_dispatch_midi_events();
-    void handle_parameters();
-    void handle_process_replacing();
-
     /**
      * Forward the host callback made by the plugin to the host and return the
      * results.
@@ -149,6 +142,11 @@ class Vst2Bridge {
      */
     std::optional<VstTimeInfo> time_info;
 
+    /**
+     * The path to the .dll being loaded in the Wine VST host.
+     */
+    const boost::filesystem::path vst_plugin_path;
+
    private:
     /**
      * A wrapper around `plugin->dispatcher` that handles the opening and
@@ -166,7 +164,7 @@ class Vst2Bridge {
      * message handling can be performed from a single thread, even when hosting
      * multiple plugins.
      */
-    boost::asio::io_context& io_context;
+    MainContext& main_context;
 
     /**
      * The configuration for this instance of yabridge based on the `.so` file
@@ -188,49 +186,6 @@ class Vst2Bridge {
      */
     AEffect* plugin;
 
-    /**
-     * The UNIX domain socket endpoint used for communicating to this specific
-     * bridged plugin.
-     */
-    boost::asio::local::stream_protocol::endpoint socket_endpoint;
-
-    // The naming convention for these sockets is `<from>_<to>_<event>`. For
-    // instance the socket named `host_vst_dispatch` forwards
-    // `AEffect.dispatch()` calls from the native VST host to the Windows VST
-    // plugin (through the Wine VST host).
-
-    /**
-     * The socket that forwards all `dispatcher()` calls from the VST host to
-     * the plugin.
-     */
-    boost::asio::local::stream_protocol::socket host_vst_dispatch;
-    /**
-     * Used specifically for the `effProcessEvents` opcode. This is needed
-     * because the Win32 API is designed to block during certain GUI
-     * interactions such as resizing a window or opening a dropdown. Without
-     * this MIDI input would just stop working at times.
-     */
-    boost::asio::local::stream_protocol::socket host_vst_dispatch_midi_events;
-    /**
-     * The socket that forwards all `audioMaster()` calls from the Windows VST
-     * plugin to the host.
-     */
-    boost::asio::local::stream_protocol::socket vst_host_callback;
-    /**
-     * Used for both `getParameter` and `setParameter` since they mostly
-     * overlap.
-     */
-    boost::asio::local::stream_protocol::socket host_vst_parameters;
-    boost::asio::local::stream_protocol::socket host_vst_process_replacing;
-
-    /**
-     * A control socket that sends data that is not suitable for the other
-     * sockets. At the moment this is only used to, on startup, send the Windows
-     * VST plugin's `AEffect` object to the native VST plugin, and to then send
-     * the configuration (from `config`) back to the Wine host.
-     */
-    boost::asio::local::stream_protocol::socket host_vst_control;
-
     /**
      * The thread that specifically handles `effProcessEvents` opcodes so the
      * plugin can still receive MIDI during GUI interaction to work around Win32
@@ -248,11 +203,13 @@ class Vst2Bridge {
     Win32Thread process_replacing_handler;
 
     /**
-     * A binary semaphore to prevent race conditions from the host callback
-     * function being called by two threads at once. See `send_event()` for more
-     * information.
+     * All sockets used for communicating with this specific plugin.
+     *
+     * NOTE: This is defined **after** the threads on purpose. This way the
+     *       sockets will be closed first, and we can then safely wait for the
+     *       threads to exit.
      */
-    std::mutex host_callback_mutex;
+    Sockets<Win32Thread> sockets;
 
     /**
      * A scratch buffer for sending and receiving data during `process` and

src/wine-host/editor.h

@@ -44,7 +44,7 @@
  * - Melda plugins when having multiple editor windows open within a single
  *   plugin group
  */
-constexpr int max_win32_messages = 20;
+constexpr int max_win32_messages [[maybe_unused]] = 20;
 
 /**
  * Used to store the maximum width and height of a screen.

src/wine-host/individual-host.cpp

@@ -24,22 +24,9 @@
 #include "../common/utils.h"
 #include "bridges/vst2.h"
 
-using namespace std::literals::chrono_literals;
-
-/**
- * The delay between calls to the event loop at a more than cinematic 30 fps.
- */
-constexpr std::chrono::duration event_loop_interval = 1000ms / 30;
-
-/**
- * Handle both Win32 and X11 events on a timer. This is more or less a
- * simplified version of `GroupBridge::async_handle_events`.
- */
-void async_handle_events(boost::asio::steady_timer& timer, Vst2Bridge& bridge);
-
 /**
  * This is the default VST host application. It will load the specified VST2
- * plugin, and then connect back to the `libyabridge.so` instace that spawned
+ * plugin, and then connect back to the `libyabridge.so` instance that spawned
  * this over the socket.
  *
  * The explicit calling convention is needed to work around a bug introduced in
@@ -48,9 +35,9 @@ void async_handle_events(boost::asio::steady_timer& timer, Vst2Bridge& bridge);
 int __cdecl main(int argc, char* argv[]) {
     set_realtime_priority();
 
-    // We pass the name of the VST plugin .dll file to load and the Unix domain
-    // socket to connect to in plugin/bridge.cpp as the first two arguments of
-    // this process.
+    // We pass the name of the VST plugin .dll file to load and the base
+    // directory for the Unix domain socket endpoints to connect to as the first
+    // two arguments of this process in plugin/bridge.cpp.
     if (argc < 3) {
         std::cerr << "Usage: "
 #ifdef __i386__
@@ -58,7 +45,7 @@ int __cdecl main(int argc, char* argv[]) {
 #else
                   << yabridge_individual_host_name
 #endif
-                  << " <vst_plugin_dll> <unix_domain_socket>" << std::endl;
+                  << " <vst_plugin_dll> <endpoint_base_directory>" << std::endl;
 
         return 1;
     }
@@ -73,17 +60,16 @@ int __cdecl main(int argc, char* argv[]) {
               << std::endl;
 
     // As explained in `Vst2Bridge`, the plugin has to be initialized in the
-    // same thread as the one that calls `io_context.run()`. And for some
-    // reason, a lot of plugins have memory corruption issues when executing
-    // `LoadLibrary()` or some of their functions from within a `std::thread`
-    // (although the WinAPI `CreateThread()` does not have these issues). This
-    // setup is slightly more convoluted than it has to be, but doing it this
-    // way we don't need to differentiate between individually hosted plugins
-    // and plugin groups when it comes to event handling.
-    boost::asio::io_context io_context{};
+    // same thread as the one that calls `io_context.run()`. This setup is
+    // slightly more convoluted than it has to be, but doing it this way we
+    // don't need to differentiate between individually hosted plugins and
+    // plugin groups when it comes to event handling.
+    // TODO: Update documentation once we figure out if we can safely replace
+    //       MainContext again with a normal `io_context`.
+    MainContext main_context{};
     std::unique_ptr<Vst2Bridge> bridge;
     try {
-        bridge = std::make_unique<Vst2Bridge>(io_context, plugin_dll_path,
+        bridge = std::make_unique<Vst2Bridge>(main_context, plugin_dll_path,
                                               socket_endpoint_path);
     } catch (const std::runtime_error& error) {
         std::cerr << "Error while initializing Wine VST host:" << std::endl;
@@ -97,29 +83,13 @@ int __cdecl main(int argc, char* argv[]) {
 
     // We'll listen for `dispatcher()` calls on a different thread, but the
     // actual events will still be executed within the IO context
-    std::jthread dispatch_handler([&]() { bridge->handle_dispatch(); });
+    Win32Thread dispatch_handler([&]() { bridge->handle_dispatch(); });
 
     // Handle Win32 messages and X11 events on a timer, just like in
     // `GroupBridge::async_handle_events()``
-    boost::asio::steady_timer events_timer(io_context);
-    async_handle_events(events_timer, *bridge);
-
-    io_context.run();
-}
-
-void async_handle_events(boost::asio::steady_timer& timer, Vst2Bridge& bridge) {
-    // Try to keep a steady framerate, but add in delays to let other events get
-    // handled if the GUI message handling somehow takes very long.
-    timer.expires_at(std::max(timer.expiry() + event_loop_interval,
-                              std::chrono::steady_clock::now() + 5ms));
-    timer.async_wait([&](const boost::system::error_code& error) {
-        if (error.failed()) {
-            return;
-        }
-
-        bridge.handle_x11_events();
-        bridge.handle_win32_events();
-
-        async_handle_events(timer, bridge);
+    main_context.async_handle_events([&]() {
+        bridge->handle_x11_events();
+        bridge->handle_win32_events();
     });
+    main_context.run();
 }

src/wine-host/utils.cpp

@@ -16,6 +16,38 @@
 
 #include "utils.h"
 
+MainContext::MainContext() : context(), events_timer(context) {}
+
+void MainContext::run() {
+    context.run();
+}
+
+void MainContext::stop() {
+    context.stop();
+}
+
+uint32_t WINAPI
+win32_thread_trampoline(fu2::unique_function<void()>* entry_point) {
+    (*entry_point)();
+    delete entry_point;
+
+    return 0;
+}
+
+Win32Thread::Win32Thread(Win32Thread&& o) : handle(std::move(o.handle)) {}
+
+Win32Thread& Win32Thread::operator=(Win32Thread&& o) {
+    handle = std::move(o.handle);
+
+    return *this;
+}
+
+Win32Thread::~Win32Thread() {
+    if (handle) {
+        WaitForSingleObject(handle.get(), INFINITE);
+    }
+}
+
 Win32Thread::Win32Thread() : handle(nullptr, nullptr) {}
 
 Win32Timer::Win32Timer(HWND window_handle,

src/wine-host/utils.h

@@ -16,6 +16,8 @@
 
 #pragma once
 
+#include "boost-fix.h"
+
 #include <memory>
 #include <optional>
 
@@ -26,24 +28,119 @@
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
+#include <boost/asio/io_context.hpp>
+#include <function2/function2.hpp>
+
 /**
- * A simple RAII wrapper around the Win32 thread API.
+ * The delay between calls to the event loop at an even more than cinematic 30
+ * fps.
+ */
+constexpr std::chrono::duration event_loop_interval =
+    std::chrono::milliseconds(1000) / 30;
+
+/**
+ * A wrapper around `boost::asio::io_context()` to serve as the application's
+ * main IO context. A single instance is shared for all plugins in a plugin
+ * group so that several important events can be handled on the main thread,
+ * which can be required because in the Win32 model all GUI related operations
+ * have to be handled from the same thread. This will be run from the
+ * application's main thread.
+ */
+class MainContext {
+   public:
+    MainContext();
+
+    /**
+     * Run the IO context. This rest of this class assumes that this is only
+     * done from a single thread.
+     */
+    void run();
+
+    /**
+     * Drop all future work from the IO context. This does not necessarily mean
+     * that the thread that called `main_context.run()` immediatly returns.
+     */
+    void stop();
+
+    /**
+     * Start a timer to handle events every `event_loop_interval` milliseconds.
+     * `message_loop_active()` will return `true` while `handler` is being
+     * executed.
+     *
+     * @param handler The function that should be executed in the IO context
+     *   when the timer ticks. This should be a function that handles both the
+     *   X11 events and the Win32 message loop.
+     */
+    template <typename F>
+    void async_handle_events(F handler) {
+        // Try to keep a steady framerate, but add in delays to let other events
+        // get handled if the GUI message handling somehow takes very long.
+        events_timer.expires_at(std::max(
+            events_timer.expiry() + event_loop_interval,
+            std::chrono::steady_clock::now() + std::chrono::milliseconds(5)));
+        events_timer.async_wait(
+            [&, handler](const boost::system::error_code& error) {
+                if (error.failed()) {
+                    return;
+                }
+
+                event_loop_active = true;
+                handler();
+                event_loop_active = false;
+
+                async_handle_events(handler);
+            });
+    }
+
+    /**
+     * Is `true` if the context is currently handling the Win32 message loop and
+     * incoming `dispatch()` events should be handled on their own thread (as
+     * posting them to the IO context will thus block).
+     *
+     * TODO: No longer used after the thread rework, we can probably just drop
+     *       this if everything works out
+     */
+    std::atomic_bool event_loop_active;
+
+    /**
+     * The raw IO context. Can and should be used directly for everything that's
+     * not the event handling loop.
+     */
+    boost::asio::io_context context;
+
+   private:
+    /**
+     * The timer used to periodically handle X11 events and Win32 messages.
+     */
+    boost::asio::steady_timer events_timer;
+};
+
+/**
+ * A proxy function that calls `Win32Thread::entry_point` since `CreateThread()`
+ * is not usable with lambdas directly. Calling the passed function will invoke
+ * the lambda with the arguments passed during `Win32Thread`'s constructor. This
+ * function deallocates the function after it's finished executing.
  *
- * These threads are implemented using `CreateThread` rather than `std::thread`
- * because in some cases `std::thread` in winelib causes very hard to debug data
- * races within plugins such as Serum. This might be caused by calling
- * conventions being handled differently.
+ * We can't store the function pointer in the `Win32Thread` object because
+ * moving a `Win32Thread` object would then cause issues.
  *
- * This somewhat mimicks `std::thread`, with the following differences:
+ * @param entry_point A `fu2::unique_function<void()>*` pointer to a function
+ *   pointer, great.
+ */
+uint32_t WINAPI
+win32_thread_trampoline(fu2::unique_function<void()>* entry_point);
+
+/**
+ * A simple RAII wrapper around the Win32 thread API that imitates
+ * `std::jthread`, including implicit joining (or waiting, since this is Win32)
+ * on destruction.
  *
- * - The threads will immediatly be killed silently when a `Win32Thread` object
- *   goes out of scope. This is the desired behavior in our case since the host
- *   will have already saved chunk data before closing the plugin and this
- *   ensures that the plugin shuts down quickly.
- * - This does not accept lambdas because we're calling a C function that
- *   expects a function pointer of type `LPTHREAD_START_ROUTINE`. GCC supports
- *   converting stateless lambdas to this format, but clang (as used for IDE
- *   tooling) does not.
+ * `std::thread` uses pthreads directly in Winelib (since this is technically a
+ * regular Linux application). This means that when using
+ * `std::thread`/`std::jthread` directly, some thread local information that
+ * `CreateThread()` would normally set does not get initialized. This could then
+ * lead to memory errors. This wrapper aims to be equivalent to `std::jthread`,
+ * but using the Win32 API instead.
  *
  * @note This should be used instead of `std::thread` or `std::jthread` whenever
  *   the thread directly calls third party library code, i.e. `LoadLibrary()`,
@@ -58,18 +155,44 @@ class Win32Thread {
     Win32Thread();
 
     /**
-     * Constructor that immediately starts running the thread
+     * Constructor that immediately starts running the thread. This works
+     * equivalently to `std::jthread`.
      *
      * @param entry_point The thread entry point that should be run.
      * @param parameter The parameter passed to the entry point function.
-
-     * @tparam F A function type that should be convertible to a
-     *   `LPTHREAD_START_ROUTINE` function pointer.
      */
-    template <typename F>
-    Win32Thread(F entry_point, void* parameter)
-        : handle(CreateThread(nullptr, 0, entry_point, parameter, 0, nullptr),
-                 CloseHandle) {}
+    template <typename Function, typename... Args>
+    Win32Thread(Function&& f, Args&&... args)
+        : handle(
+              CreateThread(
+                  nullptr,
+                  0,
+                  reinterpret_cast<LPTHREAD_START_ROUTINE>(
+                      win32_thread_trampoline),
+                  // `std::function` does not support functions with move
+                  // captures the function has to be copy-constructable.
+                  // Function2's unique_function lets us capture and move our
+                  // arguments to the lambda so we don't end up with dangling
+                  // references.
+                  new fu2::unique_function<void()>(
+                      [f = std::move(f), ... args = std::move(args)]() mutable {
+                          f(std::move(args)...);
+                      }),
+                  0,
+                  nullptr),
+              CloseHandle) {}
+
+    /**
+     * Join (or wait on, since this is WIn32) the thread on shutdown, just like
+     * `std::jthread` does.
+     */
+    ~Win32Thread();
+
+    Win32Thread(const Win32Thread&) = delete;
+    Win32Thread& operator=(const Win32Thread&) = delete;
+
+    Win32Thread(Win32Thread&&);
+    Win32Thread& operator=(Win32Thread&&);
 
    private:
     /**

subprojects/function2.wrap

@@ -0,0 +1,10 @@
+[wrap-file]
+directory = function2-4.1.0
+
+source_url = https://github.com/Naios/function2/archive/4.1.0.tar.gz
+source_filename = function2-4.1.0.tar.gz
+source_hash = c3aaeaf93bf90c0f4505a18f1094b51fe28881ce202c3bf78ec4efb336c51981
+
+patch_url = file:./subprojects/function2-patch-4.1.0.tar.xz
+patch_filename = function2-patch-4.1.0.tar.xz
+patch_hash = 4b966afd862413ea1f3d96484e74401992ec958f1ee2b4cc161f3cb7c36fe7ba

tools/yabridgectl/src/utils.rs

@@ -31,9 +31,9 @@ use textwrap::Wrapper;
 use crate::config::{Config, KnownConfig};
 
 /// (Part of) the expected output when running `yabridge-host.exe`. Used to verify that everything's
-/// working correctly.
-const YABRIDGE_HOST_EXPECTED_OUTPUT: &str =
-    "Usage: yabridge-host.exe <vst_plugin_dll> <unix_domain_socket>";
+/// working correctly. We'll only match this prefix so we can modify the exact output at a later
+/// moment without causing issues.
+const YABRIDGE_HOST_EXPECTED_OUTPUT_PREFIX: &str = "Usage: yabridge-";
 
 /// Wrapper around [`std::fs::copy()`](std::fs::copy) with a human readable error message.
 pub fn copy<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> Result<u64> {
@@ -220,7 +220,7 @@ pub fn verify_wine_setup(config: &mut Config) -> Result<()> {
     let mut success = false;
     let mut last_error: Option<&str> = None;
     for line in stderr.lines() {
-        if line == YABRIDGE_HOST_EXPECTED_OUTPUT {
+        if line.starts_with(YABRIDGE_HOST_EXPECTED_OUTPUT_PREFIX) {
             success = true;
             break;
         }