Handle mutual recursion in context menus

REAPER will call `getState()` while the context menu is open, and that
also has to be handled from the GUI thread.

CHANGELOG.md

@@ -71,6 +71,8 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 - Fixed _FabFilter_ VST3 plugins freezing in **Ardour** and **Mixbus** when
   trying to duplicate existing instances of the plugin while the GUI editor is
   open.
+- Fixed a regression where REAPER would freeze when opening a VST3 plugin
+  context menu.
 - _PSPaudioware InifniStrip_ would fail to initialize because the plugin expects
   the host to always be using Microsoft COM and it won't initialize it by
   itself. InfiniStrip loads as expected now.

src/wine-host/bridges/vst3-impls/context-menu-proxy.cpp

@@ -114,7 +114,10 @@ tresult PLUGIN_API Vst3ContextMenuProxyImpl::removeItem(
 
 tresult PLUGIN_API Vst3ContextMenuProxyImpl::popup(Steinberg::UCoord x,
                                                    Steinberg::UCoord y) {
-    return bridge.send_message(
+    // NOTE: This requires mutual recursion, because REAPER will call
+    //       `getState()` whle the context menu is open, and `getState()` also
+    //       has to be handled from the GUi thread
+    return bridge.send_mutually_recursive_message(
         YaContextMenu::Popup{.owner_instance_id = owner_instance_id(),
                              .context_menu_id = context_menu_id(),
                              .x = x,

src/wine-host/bridges/vst3.cpp

@@ -253,22 +253,21 @@ void Vst3Bridge::run() {
                 -> Vst3PluginProxy::GetState::Response {
                 // NOTE: The VST3 version of Algonaut Atlas doesn't restore
                 //       state unless this function is run from the GUI thread
+                // NOTE: This also requires mutual recursion because REAPER will
+                //       call `getState()` while opening a popup menu
                 const tresult result =
-                    main_context
-                        .run_in_context<tresult>([&]() {
-                            // This same function is defined in both
-                            // `IComponent` and `IEditController`, so the host
-                            // is calling one or the other
-                            if (object_instances[request.instance_id]
-                                    .component) {
-                                return object_instances[request.instance_id]
-                                    .component->getState(&request.state);
-                            } else {
-                                return object_instances[request.instance_id]
-                                    .edit_controller->getState(&request.state);
-                            }
-                        })
-                        .get();
+                    do_mutual_recursion_on_gui_thread<tresult>([&]() {
+                        // This same function is defined in both `IComponent`
+                        // and `IEditController`, so the host is calling one or
+                        // the other
+                        if (object_instances[request.instance_id].component) {
+                            return object_instances[request.instance_id]
+                                .component->getState(&request.state);
+                        } else {
+                            return object_instances[request.instance_id]
+                                .edit_controller->getState(&request.state);
+                        }
+                    });
 
                 return Vst3PluginProxy::GetStateResponse{
                     .result = result, .state = std::move(request.state)};