Add mouse wheel support to UI list boxes

Allows scrolling server browser list and some other lists.

code/q3_ui/ui_qmenu.c

@@ -1034,6 +1034,50 @@ sfxHandle_t ScrollList_Key( menulist_s *l, int key )
 			}
 			return (menu_buzz_sound);
 
+		case K_MWHEELUP:
+			if( l->columns > 1 ) {
+				return menu_null_sound;
+			}
+
+			if (l->top > 0)
+			{
+				// if scrolling 3 lines would replace over half of the
+				// displayed items, only scroll 1 item at a time.
+				int scroll = l->height < 6 ? 1 : 3;
+				l->top -= scroll;
+				if (l->top < 0)
+					l->top = 0;
+
+				if (l->generic.callback)
+					l->generic.callback( l, QM_GOTFOCUS );
+
+				// make scrolling silent
+				return (menu_null_sound);
+			}
+			return (menu_buzz_sound);
+
+		case K_MWHEELDOWN:
+			if( l->columns > 1 ) {
+				return menu_null_sound;
+			}
+
+			if (l->top < l->numitems-l->height)
+			{
+				// if scrolling 3 items would replace over half of the
+				// displayed items, only scroll 1 item at a time.
+				int scroll = l->height < 6 ? 1 : 3;
+				l->top += scroll;
+				if (l->top > l->numitems-l->height)
+					l->top = l->numitems-l->height;
+
+				if (l->generic.callback)
+					l->generic.callback( l, QM_GOTFOCUS );
+
+				// make scrolling silent
+				return (menu_null_sound);
+			}
+			return (menu_buzz_sound);
+
 		case K_KP_UPARROW:
 		case K_UPARROW:
 			if( l->curvalue == 0 ) {

code/ui/ui_shared.c

@@ -1828,6 +1828,27 @@ qboolean Item_ListBox_HandleKey(itemDef_t *item, int key, qboolean down, qboolea
 				return qtrue;
 			}
 		}
+
+		// Use mouse wheel in vertical and horizontal menus.
+		// If scrolling 3 items would replace over half of the
+		// displayed items, only scroll 1 item at a time.
+		if ( key == K_MWHEELUP ) {
+			int scroll = viewmax < 6 ? 1 : 3;
+			listPtr->startPos -= scroll;
+			if (listPtr->startPos < 0) {
+				listPtr->startPos = 0;
+			}
+			return qtrue;
+		}
+		if ( key == K_MWHEELDOWN ) {
+			int scroll = viewmax < 6 ? 1 : 3;
+			listPtr->startPos += scroll;
+			if (listPtr->startPos > max) {
+				listPtr->startPos = max;
+			}
+			return qtrue;
+		}
+
 		// mouse hit
 		if (key == K_MOUSE1 || key == K_MOUSE2) {
 			if (item->window.flags & WINDOW_LB_LEFTARROW) {