output/Command: flush the mixer cache when enabling/disabling output

NEWS

@@ -5,6 +5,8 @@ ver 0.19.11 (not yet released)
   - ffmpeg: fix crash due to wrong avio_alloc_context() call
 * encoder
   - flac: fix crash with 32 bit playback
+* mixer
+  - fix mixer lag after enabling/disabling output
 
 ver 0.19.10 (2015/06/21)
 * input

src/output/OutputCommand.cxx

@@ -30,6 +30,7 @@
 #include "Internal.hxx"
 #include "PlayerControl.hxx"
 #include "mixer/MixerControl.hxx"
+#include "mixer/Volume.hxx"
 #include "Idle.hxx"
 
 extern unsigned audio_output_state_version;
@@ -47,6 +48,11 @@ audio_output_enable_index(MultipleOutputs &outputs, unsigned idx)
 	ao.enabled = true;
 	idle_add(IDLE_OUTPUT);
 
+	if (ao.mixer != nullptr) {
+		InvalidateHardwareVolume();
+		idle_add(IDLE_MIXER);
+	}
+
 	ao.player_control->UpdateAudio();
 
 	++audio_output_state_version;
@@ -70,6 +76,7 @@ audio_output_disable_index(MultipleOutputs &outputs, unsigned idx)
 	Mixer *mixer = ao.mixer;
 	if (mixer != nullptr) {
 		mixer_close(mixer);
+		InvalidateHardwareVolume();
 		idle_add(IDLE_MIXER);
 	}
 
@@ -94,6 +101,7 @@ audio_output_toggle_index(MultipleOutputs &outputs, unsigned idx)
 		Mixer *mixer = ao.mixer;
 		if (mixer != nullptr) {
 			mixer_close(mixer);
+			InvalidateHardwareVolume();
 			idle_add(IDLE_MIXER);
 		}
 	}