output/Control: add method Configure()

src/output/Control.cxx

@@ -44,6 +44,12 @@ AudioOutputControl::AudioOutputControl(AudioOutput *_output)
 {
 }
 
+void
+AudioOutputControl::Configure(const ConfigBlock &block)
+{
+	(void)block;
+}
+
 const char *
 AudioOutputControl::GetName() const
 {

src/output/Control.hxx

@@ -38,6 +38,7 @@
 enum class ReplayGainMode : uint8_t;
 struct AudioOutput;
 struct MusicChunk;
+struct ConfigBlock;
 class MusicPipe;
 class Mutex;
 class Mixer;
@@ -158,6 +159,11 @@ public:
 	AudioOutputControl(const AudioOutputControl &) = delete;
 	AudioOutputControl &operator=(const AudioOutputControl &) = delete;
 
+	/**
+	 * Throws #std::runtime_error on error.
+	 */
+	void Configure(const ConfigBlock &block);
+
 	gcc_pure
 	const char *GetName() const;
 

src/output/MultipleOutputs.cxx

@@ -75,7 +75,18 @@ LoadOutputControl(EventLoop &event_loop,
 	auto *output = LoadOutput(event_loop, replay_gain_config,
 				  mixer_listener,
 				  client, block);
-	return new AudioOutputControl(output);
+	auto *control = new AudioOutputControl(output);
+
+	try {
+		control->Configure(block);
+	} catch (...) {
+		control->BeginDestroy();
+		control->FinishDestroy();
+		delete control;
+		throw;
+	}
+
+	return control;
 }
 
 void