Allow creating plugins instances

src/plugin/bridges/clap-impls/plugin-factory-proxy.cpp

@@ -56,6 +56,43 @@ clap_plugin_factory_proxy::plugin_factory_create_plugin(
     const struct clap_plugin_factory* factory,
     const clap_host_t* host,
     const char* plugin_id) {
-    // TODO: Implement
-    return nullptr;
+    assert(factory && host && plugin_id);
+    auto self = reinterpret_cast<const clap_plugin_factory_proxy*>(factory);
+
+    // We'll need to store another copy of this descriptor in the plugin
+    // instance
+    const auto descriptor =
+        std::find_if(self->descriptors_.begin(), self->descriptors_.end(),
+                     [plugin_id](const auto& descriptor) {
+                         return descriptor.id == plugin_id;
+                     });
+    if (descriptor == self->descriptors_.end()) {
+        self->bridge_.logger_.log_trace([&]() {
+            return "The host tried to create an instance for ID \"" +
+                   std::string(plugin_id) +
+                   "\", but we don't have a descriptor for this plugin.";
+        });
+
+        return nullptr;
+    }
+
+    const clap::plugin_factory::CreateResponse response =
+        self->bridge_.send_main_thread_message(clap::plugin_factory::Create{
+            .host = *host, .plugin_id = plugin_id});
+    if (response.instance_id) {
+        // This plugin proxy is tied to the instance ID created on the Wine
+        // side. That way we can link function calls from the host to the
+        // correct plugin instance, and callbacks made from the plugin to the
+        // correct host instance.
+        self->bridge_.register_plugin_proxy(std::make_unique<clap_plugin_proxy>(
+            self->bridge_, *response.instance_id, *descriptor));
+
+        const auto& [plugin_proxy, _] =
+            self->bridge_.get_proxy(*response.instance_id);
+
+        return plugin_proxy.plugin_vtable();
+    } else {
+        // The plugin couldn't be created, for whatever reason that might be
+        return nullptr;
+    }
 }