yabridge/src/plugin/bridges/clap-impls/plugin-proxy.h

// yabridge: a Wine plugin bridge
// Copyright (C) 2020-2022 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 <future>
#include <thread>
#include <vector>

#include <clap/ext/audio-ports.h>
#include <clap/ext/gui.h>
#include <clap/ext/latency.h>
#include <clap/ext/log.h>
#include <clap/ext/note-ports.h>
#include <clap/ext/params.h>
#include <clap/ext/state.h>
#include <clap/ext/tail.h>
#include <clap/plugin.h>
#include <rigtorp/MPMCQueue.h>
#include <function2/function2.hpp>

#include "../../common/serialization/clap/plugin.h"

// Forward declaration to avoid circular includes
class ClapPluginBridge;

/**
 * Pointers to all of a CLAP host's extension structs. These will be null if the
 * host doesn't support the extensions.
 *
 * @relates clap_plugin_proxy
 */
struct ClapHostExtensions {
    /**
     * Query all of the host's extensions. This can only be done after the
     * call to init.
     */
    ClapHostExtensions(const clap_host& host) noexcept;

    /**
     * The default constructor that assumes the host doesn't support any
     * extensions. We may only query the extensions after the plugin has called
     * `clap_plugin::init()`.
     */
    ClapHostExtensions() noexcept;

    /**
     * Get the supported extensions as boolean values for serialization
     * purposes.
     */
    clap::host::SupportedHostExtensions supported() const noexcept;

    const clap_host_audio_ports_t* audio_ports = nullptr;
    const clap_host_gui_t* gui = nullptr;
    const clap_host_latency_t* latency = nullptr;
    const clap_host_log_t* log = nullptr;
    const clap_host_note_ports_t* note_ports = nullptr;
    const clap_host_params_t* params = nullptr;
    const clap_host_state_t* state = nullptr;
    const clap_host_tail_t* tail = nullptr;
};

/**
 * A proxy for a `clap_plugin`.
 */
class clap_plugin_proxy {
   public:
    /**
     * A function that can be called on the host's main thread through a
     * combination of `clap_host::request_callback()` and
     * `clap_plugin::on_main_thread()`. This is identical to
     * `fu2::unique_function<void()>` except that it doesn't throw and is
     * noexcept move assignable. That is a requirement for using these in the
     * MPMC queue.
     */
    using HostCallback = fu2::
        function_base<true, false, fu2::capacity_default, false, true, void()>;

    /**
     * Construct a proxy for a plugin that has already been created on the Wine
     * side. This is done in our `clap_plugin_factory::create()` implementation.
     * The instance ID lets us link calls the host makes on a plugin object to a
     * Windows CLAP plugin running under the Wine plugin host.
     */
    clap_plugin_proxy(ClapPluginBridge& bridge,
                      size_t instance_id,
                      clap::plugin::Descriptor descriptor,
                      const clap_host_t* host);

    clap_plugin_proxy(const clap_plugin_proxy&) = delete;
    clap_plugin_proxy& operator=(const clap_plugin_proxy&) = delete;
    clap_plugin_proxy(clap_plugin_proxy&&) = delete;
    clap_plugin_proxy& operator=(clap_plugin_proxy&&) = delete;

    /**
     * Get a `clap_plugin` vtable that can be passed to the host when creating a
     * plugin instance.
     */
    inline const clap_plugin_t* plugin_vtable() const {
        return &plugin_vtable_;
    }

    /**
     * The instance ID of the plugin instance this proxy belongs to.
     */
    inline size_t instance_id() const { return instance_id_; }

    /**
     * Asynchronously run a function on the host's main thread, returning the
     * result as a future.
     */
    template <std::invocable F>
    std::future<std::invoke_result_t<F>> run_on_main_thread(F&& fn) {
        using Result = std::invoke_result_t<F>;

        std::promise<Result> response_promise{};
        std::future<Result> response_future = response_promise.get_future();
        pending_callbacks_.push(HostCallback(
            [fn = std::forward<F>(fn),
             response_promise = std::move(response_promise)]() mutable {
                if constexpr (std::is_void_v<Result>) {
                    fn();
                    response_promise.set_value();
                } else {
                    response_promise.set_value(fn());
                }
            }));

        // In theory the host will now call `clap_plugin::on_main_thread()`,
        // where we can pop the function from the queue
        host_->request_callback(host_);

        return response_future;
    }

    /**
     * The `clap_host_t*` passed when creating the instance. Any callbacks made
     * by the proxied plugin instance must go through here.
     */
    const clap_host_t* host_;

    /**
     * The host's supported extensions. These will be populated in the
     * `clap_plugin::init()` call.
     */
    ClapHostExtensions host_extensions_;

    /**
     * A handler for receiving audio thread callbacks. Set when initializing the
     * plugin. This is needed to minimize blocking during those callbacks, as
     * certain CLAP extensions allow callbacks on the audio thread.
     */
    std::jthread audio_thread_handler_;

   protected:
    static bool CLAP_ABI plugin_init(const struct clap_plugin* plugin);
    static void CLAP_ABI plugin_destroy(const struct clap_plugin* plugin);
    static bool CLAP_ABI plugin_activate(const struct clap_plugin* plugin,
                                         double sample_rate,
                                         uint32_t min_frames_count,
                                         uint32_t max_frames_count);
    static void CLAP_ABI plugin_deactivate(const struct clap_plugin* plugin);
    static bool CLAP_ABI
    plugin_start_processing(const struct clap_plugin* plugin);
    static void CLAP_ABI
    plugin_stop_processing(const struct clap_plugin* plugin);
    static void CLAP_ABI plugin_reset(const struct clap_plugin* plugin);
    static clap_process_status CLAP_ABI
    plugin_process(const struct clap_plugin* plugin,
                   const clap_process_t* process);
    static const void* CLAP_ABI
    plugin_get_extension(const struct clap_plugin* plugin, const char* id);
    static void CLAP_ABI
    plugin_on_main_thread(const struct clap_plugin* plugin);

    static uint32_t CLAP_ABI ext_audio_ports_count(const clap_plugin_t* plugin,
                                                   bool is_input);
    static bool CLAP_ABI ext_audio_ports_get(const clap_plugin_t* plugin,
                                             uint32_t index,
                                             bool is_input,
                                             clap_audio_port_info_t* info);

    static bool CLAP_ABI ext_gui_is_api_supported(const clap_plugin_t* plugin,
                                                  const char* api,
                                                  bool is_floating);
    static bool CLAP_ABI ext_gui_get_preferred_api(const clap_plugin_t* plugin,
                                                   const char** api,
                                                   bool* is_floating);
    static bool CLAP_ABI ext_gui_create(const clap_plugin_t* plugin,
                                        const char* api,
                                        bool is_floating);
    static void CLAP_ABI ext_gui_destroy(const clap_plugin_t* plugin);
    static bool CLAP_ABI ext_gui_set_scale(const clap_plugin_t* plugin,
                                           double scale);
    static bool CLAP_ABI ext_gui_get_size(const clap_plugin_t* plugin,
                                          uint32_t* width,
                                          uint32_t* height);
    static bool CLAP_ABI ext_gui_can_resize(const clap_plugin_t* plugin);
    static bool CLAP_ABI
    ext_gui_get_resize_hints(const clap_plugin_t* plugin,
                             clap_gui_resize_hints_t* hints);
    static bool CLAP_ABI ext_gui_adjust_size(const clap_plugin_t* plugin,
                                             uint32_t* width,
                                             uint32_t* height);
    static bool CLAP_ABI ext_gui_set_size(const clap_plugin_t* plugin,
                                          uint32_t width,
                                          uint32_t height);
    static bool CLAP_ABI ext_gui_set_parent(const clap_plugin_t* plugin,
                                            const clap_window_t* window);
    static bool CLAP_ABI ext_gui_set_transient(const clap_plugin_t* plugin,
                                               const clap_window_t* window);
    static void CLAP_ABI ext_gui_suggest_title(const clap_plugin_t* plugin,
                                               const char* title);
    static bool CLAP_ABI ext_gui_show(const clap_plugin_t* plugin);
    static bool CLAP_ABI ext_gui_hide(const clap_plugin_t* plugin);

    static uint32_t CLAP_ABI ext_latency_get(const clap_plugin_t* plugin);

    static uint32_t CLAP_ABI ext_note_ports_count(const clap_plugin_t* plugin,
                                                  bool is_input);
    static bool CLAP_ABI ext_note_ports_get(const clap_plugin_t* plugin,
                                            uint32_t index,
                                            bool is_input,
                                            clap_note_port_info_t* info);

    static uint32_t CLAP_ABI ext_params_count(const clap_plugin_t* plugin);
    static bool CLAP_ABI ext_params_get_info(const clap_plugin_t* plugin,
                                             uint32_t param_index,
                                             clap_param_info_t* param_info);
    static bool CLAP_ABI ext_params_get_value(const clap_plugin_t* plugin,
                                              clap_id param_id,
                                              double* value);
    static bool CLAP_ABI ext_params_value_to_text(const clap_plugin_t* plugin,
                                                  clap_id param_id,
                                                  double value,
                                                  char* display,
                                                  uint32_t size);
    static bool CLAP_ABI ext_params_text_to_value(const clap_plugin_t* plugin,
                                                  clap_id param_id,
                                                  const char* display,
                                                  double* value);
    static void CLAP_ABI ext_params_flush(const clap_plugin_t* plugin,
                                          const clap_input_events_t* in,
                                          const clap_output_events_t* out);

    static bool CLAP_ABI ext_state_save(const clap_plugin_t* plugin,
                                        const clap_ostream_t* stream);
    static bool CLAP_ABI ext_state_load(const clap_plugin_t* plugin,
                                        const clap_istream_t* stream);

    static uint32_t CLAP_ABI ext_tail_get(const clap_plugin_t* plugin);

   private:
    ClapPluginBridge& bridge_;
    size_t instance_id_;
    clap::plugin::Descriptor descriptor_;

    /**
     * We'll periodically synchronize the Wine host's audio thread priority with
     * that of the host. Since the overhead from doing so does add up, we'll
     * only do this every once in a while.
     */
    time_t last_audio_thread_priority_synchronization_ = 0;

    /**
     * A shared memory object to share audio buffers between the native plugin
     * and the Wine plugin host. Copying audio is the most significant source of
     * bridging overhead during audio processing, and this way we can reduce the
     * amount of copies required to only once for the input audio, and one more
     * copy when copying the results back to the host.
     *
     * This will be set up during `clap_plugin::activate()`.
     */
    std::optional<AudioShmBuffer> process_buffers_;

    /**
     * We'll reuse the request objects for the process call so we can keep the
     * process data object (which contains vectors and other heap allocated data
     * structure) alive. We'll then just fill this object with new data every
     * processing cycle to prevent allocations. Then, we pass a
     * `MessageReference<clap::plugin::Process>` to our sockets. This together
     * with `bitisery::ext::MessageReference` will let us serialize from and to
     * existing objects without having to copy or reallocate them.
     *
     * To reduce the amount of copying during audio processing we'll write the
     * audio data to a shared memory object stored in `process_buffers_` first.
     */
    clap::plugin::Process process_request_;

    /**
     * The response object we'll get in return when we send the
     * `process_request_` object above to the Wine plugin host. This object also
     * contains heap data, so we also want to reuse this. This is initialized to
     * contain the `process_request_`'s response object so the response can be
     * deserialized in place.
     */
    clap::plugin::ProcessResponse process_response_;

    /**
     * The vtable for `clap_plugin`, requires that this object is never moved or
     * copied. We'll use the host data pointer instead of placing this vtable at
     * the start of the struct and directly casting the `clap_plugin_t*`.
     */
    const clap_plugin_t plugin_vtable_;

    // Extensions also have vtables. Whether or not we expose these to the host
    // depends on whether the plugin supported this extension when we called
    // `clap_plugin::init()`.
    const clap_plugin_audio_ports_t ext_audio_ports_vtable;
    const clap_plugin_gui_t ext_gui_vtable;
    const clap_plugin_latency_t ext_latency_vtable;
    const clap_plugin_note_ports_t ext_note_ports_vtable;
    const clap_plugin_params_t ext_params_vtable;
    const clap_plugin_state_t ext_state_vtable;
    const clap_plugin_tail_t ext_tail_vtable;

    /**
     * The extensions supported by the bridged plugin. Set after a successful
     * `clap_plugin::init()` call. We'll allow the host to query these same
     * extensions from our plugin proxy.
     */
    clap::plugin::SupportedPluginExtensions supported_extensions_;

    /**
     * Pending callbacks that must be sent to the host on the main thread. If a
     * socket needs to make a main thread function call, it will
     */
    rigtorp::MPMCQueue<HostCallback> pending_callbacks_;
};