Add manual reference counting to GetPluginFactory

Since even though we're passign raw pointers, it's expected that they
are actually `IPtr<T>`s.

src/plugin/bridges/vst3-impls.cpp

@@ -24,11 +24,14 @@ YaPluginFactoryPluginImpl::createInstance(Steinberg::FIDString /*cid*/,
                                           Steinberg::FIDString /*_iid*/,
                                           void** /*obj*/) {
     // TODO: Send a control message
-    return 0;
+    return Steinberg::kNotImplemented;
 }
 
 tresult PLUGIN_API
 YaPluginFactoryPluginImpl::setHostContext(Steinberg::FUnknown* /*context*/) {
-    // TODO: Send a control message
-    return 0;
+    // TODO: The docs don't clearly specify what this should be doing, but from
+    //       what I've seen this is only used to pass a `IHostApplication`
+    //       instance. That's used to allow the plugin to create objects in the
+    //       host.
+    return Steinberg::kNotImplemented;
 }

src/plugin/bridges/vst3.cpp

@@ -81,13 +81,24 @@ Vst3PluginBridge::Vst3PluginBridge()
             overload{[&](const WantsConfiguration&)
                          -> WantsConfiguration::Response { return config; }});
     });
-
-    // Set up the plugin factory, since this is the first thing the host will
-    // request after loading the module. Host callback handlers should have
-    // started before this since the Wine plugin host will request a copy of the
-    // configuration during its initialization.
-    plugin_factory = std::make_unique<YaPluginFactoryPluginImpl>(*this);
-    sockets.host_vst_control.receive_into(
-        WantsPluginFactory{}, *plugin_factory,
-        std::pair<Vst3Logger&, bool>(logger, true));
+}
+
+Steinberg::IPluginFactory* Vst3PluginBridge::get_plugin_factory() {
+    // Even though we're working with raw pointers here, we should pretend that
+    // we're `IPtr<Steinberg::IPluginFactory>` and do the reference counting
+    // ourselves because you can't always safely pass those around
+    if (plugin_factory) {
+        plugin_factory->addRef();
+    } else {
+        // Set up the plugin factory, since this is the first thing the host
+        // will request after loading the module. Host callback handlers should
+        // have started before this since the Wine plugin host will request a
+        // copy of the configuration during its initialization.
+        plugin_factory = std::make_unique<YaPluginFactoryPluginImpl>(*this);
+        sockets.host_vst_control.receive_into(
+            WantsPluginFactory{}, *plugin_factory,
+            std::pair<Vst3Logger&, bool>(logger, true));
+    }
+
+    return plugin_factory.get();
 }

src/plugin/bridges/vst3.h

@@ -52,6 +52,17 @@ class Vst3PluginBridge : PluginBridge<Vst3Sockets<std::jthread>> {
      */
     Vst3PluginBridge();
 
+    /**
+     * When the host loads the module it will call `GetPluginFactory()` which
+     * will in turn call this function. The idea is that we return an
+     * `IPluginFactory*` while doing all the reference counting that `IPtr<T>`
+     * would normally do for us ourselves. This means that when the host frees
+     * its last instance of this factory, `plugin_factory` will also be cleared.
+     *
+     * @see plugin_factory
+     */
+    Steinberg::IPluginFactory* get_plugin_factory();
+
    private:
     /**
      * Handles callbacks from the plugin to the host over the
@@ -65,16 +76,16 @@ class Vst3PluginBridge : PluginBridge<Vst3Sockets<std::jthread>> {
      */
     Vst3Logger logger;
 
-   public:
     /**
-     * Our plugin factory. This will be set up directly after initialization.
-     * All information about the plugin and its supported classes are copied
-     * directly from the Windows VST3 plugin's factory on the Wine side, and
-     * we'll provide an implementation that can send control messages to the
-     * Wine plugin host.
+     * Our plugin factory. All information about the plugin and its supported
+     * classes are copied directly from the Windows VST3 plugin's factory on the
+     * Wine side, and we'll provide an implementation that can send control
+     * messages to the Wine plugin host. Even though we're passign plain
+     * pointers around, we should pretend that they're wrapped in the VST3 SDK's
+     * reference counting p pointers so we should do the reference counting
+     * ourselves.
      *
-     * A pointer to this implementation will be returned to the host in
-     * GetPluginFactory().
+     * @related get_plugin_factory
      */
     std::unique_ptr<YaPluginFactory> plugin_factory;
 };

src/plugin/vst3-plugin.cpp

@@ -69,21 +69,5 @@ SMTG_EXPORT_SYMBOL Steinberg::IPluginFactory* PLUGIN_API GetPluginFactory() {
     // The host should have called `InitModule()` first
     assert(bridge);
 
-    // TODO: I think there is a flag that indicates that the class configuration
-    //       may change, but I don't remember if it's at runtime or every time
-    //       the module is loaded. If it's the former then this will take some
-    //       special handling.
-    return bridge->plugin_factory.get();
-
-    // TODO: In the normal implementation of this function they manually call
-    //       part of the reference counting mechanism. Is this something we also
-    //       have to? And how does the `delete self` in the `removeRef()` play
-    //       with our `std::unique_ptr` (aka, should we also use IPtr here)? The
-    //       normal implementation looks like this:
-    // if (!gPluginFactory) {
-    //     // Instantiate the factory
-    // } else {
-    //     gPluginFactory->addRef();
-    // }
-    // return gPluginFactory;
+    return bridge->get_plugin_factory();
 }