Implement YaComponentPluginImpl destructor

When the object gets dropped through the reference counting system, the
object should also be dropped in the Wine plugin host.

src/common/logging/vst3.cpp

@@ -30,6 +30,14 @@ void Vst3Logger::log_request(bool is_host_vst, const YaComponent::Create&) {
     });
 }
 
+void Vst3Logger::log_request(bool is_host_vst,
+                             const YaComponent::Destroy& request) {
+    log_request_base(is_host_vst, [&](auto& message) {
+        message << "<IPluginFactory* #" << request.instance_id
+                << ">::~IPluginFactory()";
+    });
+}
+
 void Vst3Logger::log_request(bool is_host_vst, const WantsConfiguration&) {
     log_request_base(is_host_vst, [](auto& message) {
         message << "Requesting <Configuration>";
@@ -42,6 +50,10 @@ void Vst3Logger::log_request(bool is_host_vst, const WantsPluginFactory&) {
     });
 }
 
+void Vst3Logger::log_response(bool is_host_vst, const Ack&) {
+    log_response_base(is_host_vst, [&](auto& message) { message << "ACK"; });
+}
+
 void Vst3Logger::log_response(
     bool is_host_vst,
     const std::optional<YaComponent::CreateArgs>& args) {

src/common/logging/vst3.h

@@ -48,9 +48,11 @@ class Vst3Logger {
     // (what we'll call a control message).
 
     void log_request(bool is_host_vst, const YaComponent::Create&);
+    void log_request(bool is_host_vst, const YaComponent::Destroy&);
     void log_request(bool is_host_vst, const WantsConfiguration&);
     void log_request(bool is_host_vst, const WantsPluginFactory&);
 
+    void log_response(bool is_host_vst, const Ack&);
     void log_response(bool is_host_vst,
                       const std::optional<YaComponent::CreateArgs>&);
     void log_response(bool is_host_vst, const Configuration&);

src/common/serialization/vst3.h

@@ -68,7 +68,8 @@ struct WantsPluginFactory {
  * encodes the information we request or the operation we want to perform. A
  * request of type `ControlRequest(T)` should send back a `T::Response`.
  */
-using ControlRequest = std::variant<YaComponent::Create, WantsPluginFactory>;
+using ControlRequest =
+    std::variant<YaComponent::Create, YaComponent::Destroy, WantsPluginFactory>;
 
 template <typename S>
 void serialize(S& s, ControlRequest& payload) {

src/common/serialization/vst3/base.h

@@ -34,3 +34,12 @@ using Steinberg::TBool, Steinberg::int8, Steinberg::int32, Steinberg::tresult;
 using ArrayUID = std::array<
     std::remove_reference_t<decltype(std::declval<Steinberg::TUID>()[0])>,
     std::extent_v<Steinberg::TUID>>;
+
+/**
+ * Empty struct for when we have send a response to some operation without any
+ * result values.
+ */
+struct Ack {
+    template <typename S>
+    void serialize(S&) {}
+};

src/common/serialization/vst3/component.h

@@ -93,6 +93,22 @@ class YaComponent : public Steinberg::Vst::IComponent {
         }
     };
 
+    /**
+     * Message to request the Wine plugin host to destroy the IComponent
+     * instance with the given instance ID. Sent from the destructor of
+     * `YaComponentPluginImpl`.
+     */
+    struct Destroy {
+        using Response = Ack;
+
+        native_size_t instance_id;
+
+        template <typename S>
+        void serialize(S& s) {
+            s.value8b(instance_id);
+        }
+    };
+
     /**
      * Instantiate this instance with arguments read from another interface
      * implementation.
@@ -136,11 +152,8 @@ class YaComponent : public Steinberg::Vst::IComponent {
     virtual tresult PLUGIN_API
     getState(Steinberg::IBStream* state) override = 0;
 
-   private:
+   protected:
     CreateArgs arguments;
-
-    // TODO: As explained in a few other places, `YaComponent` objects should be
-    //       assigned a unique ID for identification
 };
 
 template <typename S>

src/plugin/bridges/vst3-impls/component.cpp

@@ -21,7 +21,8 @@ YaComponentPluginImpl::YaComponentPluginImpl(Vst3PluginBridge& bridge,
     : YaComponent(std::move(args)), bridge(bridge) {}
 
 YaComponentPluginImpl::~YaComponentPluginImpl() {
-    // TODO: Send a control message to destroy the instance on the Wine side
+    bridge.send_message(
+        YaComponent::Destroy{.instance_id = arguments.instance_id});
 }
 
 tresult PLUGIN_API

src/wine-host/bridges/vst3.cpp

@@ -70,6 +70,13 @@ void Vst3Bridge::run() {
                     return std::nullopt;
                 }
             },
+            [&](const YaComponent::Destroy& request)
+                -> YaComponent::Destroy::Response {
+                std::lock_guard lock(component_instances_mutex);
+                component_instances.erase(request.instance_id);
+
+                return Ack{};
+            },
             [&](const WantsPluginFactory&) -> WantsPluginFactory::Response {
                 return *plugin_factory;
             }});