Also use mutual recursion for program list changes

The VST3 version of Voxengo TEOTE would deadlock in Ardour when Ardour
calls `IEditController::setState()`, the plugin calls
`IUnitHandler::notifyProgramListChange()` in response, and then when
Ardour calls `IUnitInfo::getProgramName()` while handling that callback.
All of these functions have to be called from the same thread in Voxengo
plugins.

CHANGELOG.md

@@ -93,6 +93,8 @@ Versioning](https://semver.org/spec/v2.0.0.html).
   open.
 - Fixed VST3 plugins freezing in **Ardour** and **Mixbus** when the plugin tries
   to automate a parameter while loading a preset.
+- Fixed _Voxengo_ VST3 plugins freezing in **Ardour** and **Mixbus** when
+  loading a project or when duplicating the plugin instances.
 - Fixed potential X11 errors resulting in assertion failures and crashes in
   **Ardour** and **Mixbus** by ignoring X11 events after those hosts hides the
   editor window.

src/wine-host/bridges/vst3-impls/component-handler-proxy.cpp

@@ -175,10 +175,14 @@ tresult PLUGIN_API Vst3ComponentHandlerProxyImpl::notifyUnitSelection(
 tresult PLUGIN_API Vst3ComponentHandlerProxyImpl::notifyProgramListChange(
     Steinberg::Vst::ProgramListID listId,
     int32 programIndex) {
-    return bridge.send_message(YaUnitHandler::NotifyProgramListChange{
-        .owner_instance_id = owner_instance_id(),
-        .list_id = listId,
-        .program_index = programIndex});
+    // NOTE: When a plugin calls this, Ardour will fetch the new program names
+    //       with `IUnitInfo::getProgramName()`. TEOTE requires this to be
+    //       called from the same thread.
+    return bridge.send_mutually_recursive_message(
+        YaUnitHandler::NotifyProgramListChange{
+            .owner_instance_id = owner_instance_id(),
+            .list_id = listId,
+            .program_index = programIndex});
 }
 
 tresult PLUGIN_API Vst3ComponentHandlerProxyImpl::notifyUnitByBusChange() {

src/wine-host/bridges/vst3.cpp

@@ -1037,10 +1037,16 @@ void Vst3Bridge::run() {
             [&](const YaUnitInfo::GetProgramName& request)
                 -> YaUnitInfo::GetProgramName::Response {
                 Steinberg::Vst::String128 name{0};
+                // NOTE: This will likely be requested in response to
+                //       `IUnitHandler::notifyProgramListChange`, but some
+                //       plugins (like TEOTE) require this to be called from the
+                //       same thread when that happens.
                 const tresult result =
-                    object_instances[request.instance_id]
-                        .unit_info->getProgramName(request.list_id,
-                                                   request.program_index, name);
+                    do_mutual_recursion_on_off_thread<tresult>([&]() {
+                        return object_instances[request.instance_id]
+                            .unit_info->getProgramName(
+                                request.list_id, request.program_index, name);
+                    });
 
                 return YaUnitInfo::GetProgramNameResponse{
                     .result = result, .name = tchar_pointer_to_u16string(name)};