Implement audioMasterGetTime,fixing playback

Midi and audio now work!

README.md

@@ -9,8 +9,6 @@ There are a few things that should be done before making this public, including:
 - Implement missing features:
   - GUIs.
   - `AEffect` updates, if that's a thing.
-  - Fix `processReplacing` forwarding. The forwarding works, but plugins don't
-    write any audio.
 - Add missing details if any to the architecture section.
 - Document what this has been tested on and what does or does not work.
 - Document wine32 support.

src/common/communication.h

@@ -144,9 +144,14 @@ class DefaultDataConverter {
         }
     }
 
-    virtual void write(const int /*opcode*/,
-                       void* data,
-                       const EventResult& response) {
+    /**
+     * Write the reponse back to the data pointer. It's also possible to
+     * override the return value, this is used in one place to return a pointer
+     * to a `VstTime` object that's contantly being updated.
+     */
+    virtual std::optional<intptr_t> write(const int /*opcode*/,
+                                          void* data,
+                                          const EventResult& response) {
         if (response.data.has_value()) {
             char* output = static_cast<char*>(data);
 
@@ -157,6 +162,8 @@ class DefaultDataConverter {
             std::copy(response.data->begin(), response.data->end(), output);
             output[response.data->size()] = 0;
         }
+
+        return std::nullopt;
     }
 };
 
@@ -214,7 +221,11 @@ intptr_t send_event(boost::asio::local::stream_protocol::socket& socket,
                                   response.data);
     }
 
-    data_converter.write(opcode, data, response);
+    const auto return_value_override =
+        data_converter.write(opcode, data, response);
+    if (return_value_override.has_value()) {
+        return return_value_override.value();
+    }
 
     return response.return_value;
 }
@@ -259,6 +270,7 @@ void passthrough_event(boost::asio::local::stream_protocol::socket& socket,
                 return &events.as_c_events();
             },
             [&](WantsChunkBuffer&) -> void* { return string_buffer.data(); },
+            [&](WantsVstTimeInfo&) -> void* { return nullptr; },
             [&](WantsString&) -> void* { return string_buffer.data(); }},
         event.payload);
 
@@ -278,6 +290,17 @@ void passthrough_event(boost::asio::local::stream_protocol::socket& socket,
                 // plugin has written
                 return std::string(*static_cast<char**>(data), return_value);
             },
+            [&](WantsVstTimeInfo&) -> std::optional<std::string> {
+                // 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!
+                // TODO: Maybe add a variant from these return types similar to
+                //       `EventPayload`, even though this is as far as I'm aware
+                //       the only non-string/buffer being returned.
+                return std::string(reinterpret_cast<const char*>(return_value),
+                                   sizeof(VstTimeInfo));
+            },
             [&](WantsString&) -> std::optional<std::string> {
                 return std::string(static_cast<char*>(data));
             },

src/common/logging.cpp

@@ -173,6 +173,7 @@ void Logger::log_event(bool is_dispatch,
                 [&](const WantsChunkBuffer&) {
                     message << "<writable_buffer>";
                 },
+                [&](const WantsVstTimeInfo&) { message << "<nullptr>"; },
                 [&](const WantsString&) { message << "<writable_string>"; }},
             payload);
 

src/common/serialization.h

@@ -117,6 +117,12 @@ class alignas(16) DynamicVstEvents {
  */
 struct WantsChunkBuffer {};
 
+/**
+ * Marker struct to indicate that the event handler will return a pointer to a
+ * `VstTiemInfo` struct that should be returned transfered.
+ */
+struct WantsVstTimeInfo {};
+
 /**
  * Marker struct to indicate that that the event requires some buffer to write
  * a C-string into.
@@ -155,6 +161,7 @@ using EventPayload = std::variant<std::nullptr_t,
                                   std::string,
                                   DynamicVstEvents,
                                   WantsChunkBuffer,
+                                  WantsVstTimeInfo,
                                   WantsString>;
 
 template <typename S>
@@ -173,7 +180,8 @@ void serialize(S& s, EventPayload& payload) {
                                            s.container1b(event.dump);
                                        });
                        },
-                       [](S&, WantsChunkBuffer&) {}, [](S&, WantsString&) {}});
+                       [](S&, WantsChunkBuffer&) {},
+                       [](S&, WantsVstTimeInfo&) {}, [](S&, WantsString&) {}});
 }
 
 /**

src/plugin/host-bridge.cpp

@@ -182,7 +182,9 @@ class DispatchDataConverter : DefaultDataConverter {
         }
     }
 
-    void write(const int opcode, void* data, const EventResult& response) {
+    std::optional<intptr_t> write(const int opcode,
+                                  void* data,
+                                  const EventResult& response) {
         switch (opcode) {
             case effGetChunk:
                 // Write the chunk data to some publically accessible place in
@@ -192,9 +194,10 @@ class DispatchDataConverter : DefaultDataConverter {
                 chunk.assign(response.data->begin(), response.data->end());
 
                 *static_cast<void**>(data) = chunk.data();
+                return std::nullopt;
                 break;
             default:
-                DefaultDataConverter::write(opcode, data, response);
+                return DefaultDataConverter::write(opcode, data, response);
                 break;
         }
     }

src/wine-host/plugin-bridge.cpp

@@ -191,6 +191,8 @@ void PluginBridge::wait() {
 
 class HostCallbackDataConverter : DefaultDataConverter {
    public:
+    HostCallbackDataConverter(VstTimeInfo& time_info) : time(time_info) {}
+
     std::optional<EventPayload> read(const int opcode,
                                      const intptr_t value,
                                      const void* data) {
@@ -210,15 +212,37 @@ class HostCallbackDataConverter : DefaultDataConverter {
 
                 return std::nullopt;
                 break;
+            case audioMasterGetTime:
+                return WantsVstTimeInfo{};
+                break;
             default:
                 return DefaultDataConverter::read(opcode, value, data);
                 break;
         }
     }
 
-    void write(const int opcode, void* data, const EventResult& response) {
-        return DefaultDataConverter::write(opcode, data, response);
+    std::optional<intptr_t> write(const int opcode,
+                                  void* data,
+                                  const EventResult& response) {
+        switch (opcode) {
+            case audioMasterGetTime:
+                // Write the returned `VstTimeInfo` struct into a field and make
+                // the function return a poitner to it
+                // TODO: Start a time to update this on the host bridge once
+                //       it's been requested. Not sure if this is needed though!
+                time = *static_cast<const VstTimeInfo*>(
+                    static_cast<const void*>(response.data->data()));
+
+                return reinterpret_cast<intptr_t>(&time);
+                break;
+            default:
+                return DefaultDataConverter::write(opcode, data, response);
+                break;
+        }
     }
+
+   private:
+    VstTimeInfo& time;
 };
 
 intptr_t PluginBridge::host_callback(AEffect* /*plugin*/,
@@ -227,7 +251,7 @@ intptr_t PluginBridge::host_callback(AEffect* /*plugin*/,
                                      intptr_t value,
                                      void* data,
                                      float option) {
-    HostCallbackDataConverter converter;
+    HostCallbackDataConverter converter(time_info);
     return send_event(vst_host_callback, converter, opcode, index, value, data,
                       option, std::nullopt);
 }

src/wine-host/plugin-bridge.h

@@ -61,6 +61,14 @@ class PluginBridge {
 
     intptr_t host_callback(AEffect*, int, int, intptr_t, void*, float);
 
+    /**
+     * With the `audioMasterGetTime` host callback the plugin expects the return
+     * value from the calblack to be a pointer to a VstTimeInfo struct.
+     *
+     * TODO: Should this be updated automatically?
+     */
+    VstTimeInfo time_info;
+
    private:
     /**
      * The shared library handle of the VST plugin. I sadly could not get