Unify handling for *::{get,set}State

Since these functions are exactly the same, and for whatever reason they
didn't just add them to the `IPluginBase` both `IComponent` and
`IEditController`. inherit from

src/common/serialization/vst3.h

@@ -59,6 +59,8 @@ struct WantsConfiguration {
  */
 using ControlRequest = std::variant<Vst3PluginProxy::Construct,
                                     Vst3PluginProxy::Destruct,
+                                    Vst3PluginProxy::SetState,
+                                    Vst3PluginProxy::GetState,
                                     YaAudioProcessor::SetBusArrangements,
                                     YaAudioProcessor::GetBusArrangement,
                                     YaAudioProcessor::CanProcessSampleSize,
@@ -73,8 +75,6 @@ using ControlRequest = std::variant<Vst3PluginProxy::Construct,
                                     YaComponent::GetRoutingInfo,
                                     YaComponent::ActivateBus,
                                     YaComponent::SetActive,
-                                    YaComponent::SetState,
-                                    YaComponent::GetState,
                                     YaPluginBase::Initialize,
                                     YaPluginBase::Terminate,
                                     YaPluginFactory::Construct,

src/common/serialization/vst3/plugin-proxy.h

@@ -150,6 +150,58 @@ class Vst3PluginProxy : public YaAudioProcessor,
 
     DECLARE_FUNKNOWN_METHODS
 
+    // We'll define messages for functions that have identical definitions in
+    // multiple interfaces below. When the Wine plugin host process handles
+    // these it should check which of the interfaces is supported on the host.
+
+    /**
+     * Message to pass through a call to
+     * `{IComponent,IEditController}::setState(state)` to the Wine plugin host.
+     */
+    struct SetState {
+        using Response = UniversalTResult;
+
+        native_size_t instance_id;
+
+        VectorStream state;
+
+        template <typename S>
+        void serialize(S& s) {
+            s.value8b(instance_id);
+            s.object(state);
+        }
+    };
+
+    /**
+     * The response code and written state for a call to
+     * `{IComponent,IEditController}::getState(state)`.
+     */
+    struct GetStateResponse {
+        UniversalTResult result;
+        VectorStream updated_state;
+
+        template <typename S>
+        void serialize(S& s) {
+            s.object(result);
+            s.object(updated_state);
+        }
+    };
+
+    /**
+     * Message to pass through a call to
+     * `{IComponent,IEditController}::getState(state)` to the Wine plugin host.
+     */
+    struct GetState {
+        using Response = GetStateResponse;
+
+        native_size_t instance_id;
+
+        template <typename S>
+        void serialize(S& s) {
+            s.value8b(instance_id);
+        }
+    };
+
    protected:
     ConstructArgs arguments;
 };

src/common/serialization/vst3/plugin/component.h

@@ -255,57 +255,12 @@ class YaComponent : public Steinberg::Vst::IComponent {
 
     virtual tresult PLUGIN_API setActive(TBool state) override = 0;
 
-    /**
-     * Message to pass through a call to `IComponent::setState(state)` to the
-     * Wine plugin host.
-     */
-    struct SetState {
-        using Response = UniversalTResult;
-
-        native_size_t instance_id;
-
-        VectorStream state;
-
-        template <typename S>
-        void serialize(S& s) {
-            s.value8b(instance_id);
-            s.object(state);
-        }
-    };
-
+    // `setState()` and `getState()` are defiend in both `IComponent` and
+    // `IEditController`. Since an object can only ever implement one or the
+    // other, the messages for calling either are defined directly on
+    // `Vst3PluginProxy`.
     virtual tresult PLUGIN_API
     setState(Steinberg::IBStream* state) override = 0;
-
-    /**
-     * The response code and written state for a call to
-     * `IComponent::getState(state)`.
-     */
-    struct GetStateResponse {
-        UniversalTResult result;
-        VectorStream updated_state;
-
-        template <typename S>
-        void serialize(S& s) {
-            s.object(result);
-            s.object(updated_state);
-        }
-    };
-
-    /**
-     * Message to pass through a call to `IComponent::getState(state)` to the
-     * Wine plugin host.
-     */
-    struct GetState {
-        using Response = GetStateResponse;
-
-        native_size_t instance_id;
-
-        template <typename S>
-        void serialize(S& s) {
-            s.value8b(instance_id);
-        }
-    };
-
     virtual tresult PLUGIN_API
     getState(Steinberg::IBStream* state) override = 0;
 

src/common/serialization/vst3/plugin/edit-controller.h

@@ -80,10 +80,16 @@ class YaEditController2 : public Steinberg::Vst::IEditController,
 
     virtual tresult PLUGIN_API
     setComponentState(Steinberg::IBStream* state) override = 0;
+
+    // `setState()` and `getState()` are defiend in both `IComponent` and
+    // `IEditController`. Since an object can only ever implement one or the
+    // other, the messages for calling either are defined directly on
+    // `Vst3PluginProxy`.
     virtual tresult PLUGIN_API
     setState(Steinberg::IBStream* state) override = 0;
     virtual tresult PLUGIN_API
     getState(Steinberg::IBStream* state) override = 0;
+
     virtual int32 PLUGIN_API getParameterCount() override = 0;
     virtual tresult PLUGIN_API
     getParameterInfo(int32 paramIndex,