settings: add volume_change_step configuration option

doc/config

@@ -301,6 +301,8 @@
 #
 #seek_time = "1"
 #
+#volume_change_step = "1"
+#
 #autocenter_mode = "no"
 #
 #centered_cursor = "no"

doc/ncmpcpp.1

@@ -108,6 +108,9 @@ If you use encoding other than utf8, set it in order to handle utf8 encoded stri
 .B seek_time = SECONDS
 Base seek time to begin with.
 .TP 
+.B volume_change_step = NUMBER
+Number of percents volume has to be increased/decreased by in volume_up/volume_down.
+.TP 
 .B playlist_disable_highlight_delay = SECONDS
 Delay for highlighting playlist since the last key was pressed. If set to 0, highlighting never fades away.
 .TP 

src/actions.cpp

@@ -615,12 +615,14 @@ void SlaveScreen::run()
 
 void VolumeUp::run()
 {
-	Mpd.SetVolume(Mpd.GetVolume()+1);
+	int volume = std::min(Mpd.GetVolume()+Config.volume_change_step, 100);
+	Mpd.SetVolume(volume);
 }
 
 void VolumeDown::run()
 {
-	Mpd.SetVolume(Mpd.GetVolume()-1);
+	int volume = std::max(Mpd.GetVolume()-Config.volume_change_step, 0);
+	Mpd.SetVolume(volume);
 }
 
 bool DeletePlaylistItems::canBeRun() const

src/settings.cpp

@@ -224,6 +224,7 @@ void Configuration::SetDefaults()
 	mpd_connection_timeout = 15;
 	crossfade_time = 5;
 	seek_time = 1;
+	volume_change_step = 1;
 	playlist_disable_highlight_delay = 5;
 	message_delay_time = 4;
 	lyrics_db = 0;
@@ -367,6 +368,11 @@ void Configuration::Read()
 				if (boost::lexical_cast<int>(v) > 0)
 					seek_time = boost::lexical_cast<int>(v);
 			}
+			else if (name == "volume_change_step")
+			{
+				if (boost::lexical_cast<int>(v) > 0)
+					volume_change_step = boost::lexical_cast<int>(v);
+			}
 			else if (name == "playlist_disable_highlight_delay")
 			{
 				if (boost::lexical_cast<int>(v) >= 0)

src/settings.h

@@ -189,6 +189,7 @@ struct Configuration
 	int mpd_connection_timeout;
 	int crossfade_time;
 	int seek_time;
+	int volume_change_step;
 	int playlist_disable_highlight_delay;
 	int message_delay_time;
 	int lyrics_db;