Allow null pointers in IEditController::setComponentHandler

src/common/logging/vst3.cpp

@@ -306,8 +306,13 @@ bool Vst3Logger::log_request(
     const YaEditController::SetComponentHandler& request) {
     return log_request_base(is_host_vst, [&](auto& message) {
         message << request.instance_id
-                << ": IEditController::setComponentHandler(handler = "
+                << ": IEditController::setComponentHandler(handler = ";
-                   "<IComponentHandler*>)";
+        if (request.component_handler_proxy_args) {
+            message << "<IComponentHandler*>";
+        } else {
+            message << "<nullptr>";
+        }
+        message << ")";
     });
 }
 

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

@@ -344,12 +344,19 @@ class YaEditController : public Steinberg::Vst::IEditController {
 
         native_size_t instance_id;
 
-        Vst3ComponentHandlerProxy::ConstructArgs component_handler_proxy_args;
+        /**
+         * Some hosts will pass a null pointer to explicitly free the component
+         * handler passed before releasing the object instance. This also
+         * happens in the SDK, so this seems like valid behaviour we should
+         * support.
+         */
+        std::optional<Vst3ComponentHandlerProxy::ConstructArgs>
+            component_handler_proxy_args;
 
         template <typename S>
         void serialize(S& s) {
             s.value8b(instance_id);
-            s.object(component_handler_proxy_args);
+            s.ext(component_handler_proxy_args, bitsery::ext::StdOptional{});
         }
     };
 

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

@@ -452,7 +452,8 @@ Vst3PluginProxyImpl::setParamNormalized(Steinberg::Vst::ParamID id,
 
 tresult PLUGIN_API Vst3PluginProxyImpl::setComponentHandler(
     Steinberg::Vst::IComponentHandler* handler) {
-    // TODO: Null pointers are valid here, should we pass them through?
+    // Null pointers are valid here going from the reference implementations in
+    // the SDK
     if (handler) {
         // We'll store the pointer for when the plugin later makes a callback to
         // this component handler
@@ -473,10 +474,18 @@ tresult PLUGIN_API Vst3PluginProxyImpl::setComponentHandler(
                 Vst3ComponentHandlerProxy::ConstructArgs(component_handler,
                                                          instance_id())});
     } else {
-        bridge.logger.log(
+        component_handler = nullptr;
-            "WARNING: Null pointer passed to "
+
-            "'IEditController::setComponentHandler()'");
+        component_handler_2 = nullptr;
-        return Steinberg::kInvalidArgument;
+        component_handler_3 = nullptr;
+        component_handler_bus_activation = nullptr;
+        progress = nullptr;
+        unit_handler = nullptr;
+        unit_handler_2 = nullptr;
+
+        return bridge.send_message(YaEditController::SetComponentHandler{
+            .instance_id = instance_id(),
+            .component_handler_proxy_args = std::nullopt});
     }
 }
 

src/wine-host/bridges/vst3.cpp

@@ -364,14 +364,18 @@ void Vst3Bridge::run() {
             },
             [&](YaEditController::SetComponentHandler& request)
                 -> YaEditController::SetComponentHandler::Response {
-                // We'll create a proxy object for the component handler and
+                // If the host passed a valid component handler, then we'll
-                // pass that to the initialize function. The lifetime of this
+                // create a proxy object for the component handler and pass that
-                // object is tied to that of the actual plugin object we're
+                // to the initialize function. The lifetime of this object is
-                // proxying for.
+                // tied to that of the actual plugin object we're proxying for.
+                // Otherwise we'll also pass a null pointer. This often happens
+                // just before the host terminates the plugin.
                 object_instances[request.instance_id].component_handler_proxy =
-                    Steinberg::owned(new Vst3ComponentHandlerProxyImpl(
+                    request.component_handler_proxy_args
-                        *this,
+                        ? Steinberg::owned(new Vst3ComponentHandlerProxyImpl(
-                        std::move(request.component_handler_proxy_args)));
+                              *this,
+                              std::move(*request.component_handler_proxy_args)))
+                        : nullptr;
 
                 return object_instances[request.instance_id]
                     .edit_controller->setComponentHandler(