Feature #6090: Change music set during gameplay

src/settings_gui.h

@@ -13,6 +13,7 @@
 #define SETTING_GUI_H
 
 #include "gfx_type.h"
+#include "widgets/dropdown_type.h"
 
 /** Width of setting buttons */
 #define SETTING_BUTTON_WIDTH  ((int)NWidgetScrollbar::GetHorizontalDimension().width * 2)
@@ -23,5 +24,10 @@ void DrawArrowButtons(int x, int y, Colours button_colour, byte state, bool clic
 void DrawDropDownButton(int x, int y, Colours button_colour, bool state, bool clickable);
 void DrawBoolButton(int x, int y, bool state, bool clickable);
 
+DropDownList *BuildMusicSetDropDownList(int *selected_index);
+
+/* Actually implemented in music_gui.cpp */
+void ChangeMusicSet(int index);
+
 #endif /* SETTING_GUI_H */