Add a checkbox for the "stop music in background" preference

data/gui/window/preferences/04_sound.cfg

@@ -61,6 +61,40 @@
 	[/grid]
 #enddef
 
+#define _GUI_AUTO_MUTE_MUSIC_CHECKBOX
+	[row]
+		[column]
+			horizontal_grow = true
+			[grid]
+				[row]
+					[column]
+						{_GUI_PREFERENCES_CHECKBOX_ALIGN_SPACER}
+					[/column]
+
+					[column]
+						grow_factor = 0
+						border = "all"
+						border_size = 5
+						horizontal_grow = true
+
+						[toggle_button]
+							id = sound_toggle_stop_music_in_background
+							label = _ "Pause music on focus loss"
+							tooltip = _ "Pause the music when you switch to any other window"
+						[/toggle_button]
+					[/column]
+
+					[column]
+						grow_factor = 1
+						[spacer]
+						[/spacer]
+					[/column]
+				[/row]
+			[/grid]
+		[/column]
+	[/row]
+#enddef
+
 #define _GUI_PREFERENCES_SOUND_GRID
 	[row]
 		[column]
@@ -84,6 +118,8 @@
 		[/column]
 	[/row]
 
+	{_GUI_AUTO_MUTE_MUSIC_CHECKBOX}
+
 	[row]
 		[column]
 			horizontal_grow = true
@@ -121,4 +157,5 @@
 [/layer]
 
 #undef _GUI_PREFERENCES_SOUND_GRID
+#under _GUI_AUTO_MUTE_MUSIC_CHECKBOX
 #undef _GUI_SOUND_SLIDER_CONTROL

src/gui/dialogs/preferences_dialog.cpp

@@ -622,6 +622,11 @@ void tpreferences::initialize_members(twindow& window)
 		music_on(), music_volume(),
 		bind_void(set_music, _1), set_music_volume, window);
 
+	setup_single_toggle("sound_toggle_stop_music_in_background",
+		stop_music_in_background(),
+		set_stop_music_in_background,
+		window);
+
 	/* TURN BELL */
 	setup_toggle_slider_pair("sound_toggle_bell", "sound_volume_bell",
 		turn_bell(), bell_volume(),