Implement IPlugView::isPLatformTypeSupported()

This of course requires us to substitute the relevant Linux platform
type for the Win32 one.

src/common/logging/vst3.cpp

@@ -432,6 +432,21 @@ bool Vst3Logger::log_request(bool is_host_vst,
     });
 }
 
+bool Vst3Logger::log_request(
+    bool is_host_vst,
+    const YaPlugView::IsPlatformTypeSupported& request) {
+    return log_request_base(is_host_vst, [&](auto& message) {
+        message << request.owner_instance_id
+                << ": IPlugView::isPLatformTypeSupported(type = \""
+                << request.type;
+        if (request.type == Steinberg::kPlatformTypeX11EmbedWindowID) {
+            message << "\" (will be translated to \""
+                    << Steinberg::kPlatformTypeHWND << "\")";
+        }
+        message << ")";
+    });
+}
+
 bool Vst3Logger::log_request(bool is_host_vst,
                              const YaPluginBase::Initialize& request) {
     return log_request_base(is_host_vst, [&](auto& message) {

src/common/logging/vst3.h

@@ -108,6 +108,8 @@ class Vst3Logger {
     bool log_request(bool is_host_vst,
                      const YaEditController::SetComponentHandler&);
     bool log_request(bool is_host_vst, const YaEditController::CreateView&);
+    bool log_request(bool is_host_vst,
+                     const YaPlugView::IsPlatformTypeSupported&);
     bool log_request(bool is_host_vst, const YaPluginBase::Initialize&);
     bool log_request(bool is_host_vst, const YaPluginBase::Terminate&);
     bool log_request(bool is_host_vst, const YaPluginFactory::Construct&);

src/common/serialization/vst3.h

@@ -92,6 +92,7 @@ using ControlRequest = std::variant<Vst3PlugViewProxy::Destruct,
                                     YaEditController::SetParamNormalized,
                                     YaEditController::SetComponentHandler,
                                     YaEditController::CreateView,
+                                    YaPlugView::IsPlatformTypeSupported,
                                     YaPluginBase::Initialize,
                                     YaPluginBase::Terminate,
                                     YaPluginFactory::Construct,

src/common/serialization/vst3/plug-view/plug-view.h

@@ -61,6 +61,27 @@ class YaPlugView : public Steinberg::IPlugView {
 
     inline bool supported() const { return arguments.supported; }
 
+    /**
+     * Message to pass through a call to
+     * `IPlugView::isPlatformTypeSupported(type)` to the Wine plugin host. We
+     * will of course change `kPlatformStringLinux` for `kPlatformStringWin`,
+     * because why would a Windows VST3 plugin have X11 support? (and how would
+     * that even work)
+     */
+    struct IsPlatformTypeSupported {
+        using Response = UniversalTResult;
+
+        native_size_t owner_instance_id;
+
+        std::string type;
+
+        template <typename S>
+        void serialize(S& s) {
+            s.value8b(owner_instance_id);
+            s.text1b(type, 128);
+        }
+    };
+
     virtual tresult PLUGIN_API
     isPlatformTypeSupported(Steinberg::FIDString type) override = 0;
     virtual tresult PLUGIN_API attached(void* parent,