Use volume command for relative volume changes instead of setvol

src/actions.cpp

@@ -623,14 +623,12 @@ void SlaveScreen::run()
 
 void VolumeUp::run()
 {
-	int volume = std::min(Status::State::volume()+Config.volume_change_step, 100u);
-	Mpd.SetVolume(volume);
+	Mpd.ChangeVolume(static_cast<int>(Config.volume_change_step));
 }
 
 void VolumeDown::run()
 {
-	int volume = std::max(int(Status::State::volume()-Config.volume_change_step), 0);
-	Mpd.SetVolume(volume);
+	Mpd.ChangeVolume(-static_cast<int>(Config.volume_change_step));
 }
 
 bool AddItemToPlaylist::canBeRun()

src/mpdpp.cpp

@@ -472,6 +472,14 @@ void Connection::SetVolume(unsigned vol)
 	checkErrors();
 }
 
+void Connection::ChangeVolume(int change)
+{
+	prechecksNoCommandsList();
+	mpd_run_change_volume(m_connection.get(), change);
+	checkErrors();
+}
+
+
 std::string Connection::GetReplayGainMode()
 {
 	prechecksNoCommandsList();

src/mpdpp.h

@@ -536,7 +536,8 @@ struct Connection
 	void SetConsume(bool);
 	void SetCrossfade(unsigned);
 	void SetVolume(unsigned int vol);
-	
+	void ChangeVolume(int change);
+
 	std::string GetReplayGainMode();
 	void SetReplayGainMode(ReplayGainMode);