Fix #22553: dragging number buttons would run update functions more often than

necessary due to the more accurate mouse move events that are useful for
sculpting and painting (at least on Linux/X11, not sure about other platforms).
If the update function takes a while to run, this in turn causes more mouse
move events to be accumulated, making things even slower, .. going into a spiral
of slower and slower redraws.

As a solution I've added a INBETWEEN_MOUSEMOVE event next to MOUSEMOVE. A
MOUSEMOVE event is automatically changed to INBETWEEN_MOUSEMOVE when a
MOUSEMOVE event is added after it. This new event type is only handled by
painting/sculpting operators, everything else can happily ignore it.

source/blender/editors/gpencil/gpencil_paint.c

@@ -1481,6 +1481,7 @@ static int gpencil_draw_modal (bContext *C, wmOperator *op, wmEvent *event)
 		
 		/* moving mouse - assumed that mouse button is down if in painting status */
 		case MOUSEMOVE:
+		case INBETWEEN_MOUSEMOVE:
 			/* check if we're currently painting */
 			if (p->status == GP_STATUS_PAINTING) {
 				/* handle drawing event */

source/blender/editors/sculpt_paint/paint_image.c

@@ -4872,6 +4872,7 @@ static int paint_modal(bContext *C, wmOperator *op, wmEvent *event)
 			paint_exit(C, op);
 			return OPERATOR_FINISHED;
 		case MOUSEMOVE:
+		case INBETWEEN_MOUSEMOVE:
 			paint_apply_event(C, op, event);
 			break;
 		case TIMER:

source/blender/editors/sculpt_paint/paint_stroke.c

@@ -275,7 +275,7 @@ int paint_stroke_modal(bContext *C, wmOperator *op, wmEvent *event)
 		MEM_freeN(stroke);
 		return OPERATOR_FINISHED;
 	}
-	else if(first || event->type == MOUSEMOVE || (event->type == TIMER && (event->customdata == stroke->timer))) {
+	else if(first || ELEM(event->type, MOUSEMOVE, INBETWEEN_MOUSEMOVE) || (event->type == TIMER && (event->customdata == stroke->timer))) {
 		if(stroke->stroke_started) {
 			if(paint_smooth_stroke(stroke, mouse, event)) {
 				if(paint_space_stroke_enabled(stroke->brush)) {

source/blender/makesrna/intern/rna_wm.c

@@ -114,6 +114,7 @@ EnumPropertyItem event_type_items[] = {
 	{SELECTMOUSE, "SELECTMOUSE", 0, "Select Mouse", ""},
 	{0, "", 0, NULL, NULL},
 	{MOUSEMOVE, "MOUSEMOVE", 0, "Mouse Move", ""},
+	{INBETWEEN_MOUSEMOVE, "INBETWEEN_MOUSEMOVE", 0, "Inbetween Move", ""},
 	{MOUSEPAN, "TRACKPADPAN", 0, "Mouse/Trackpad Pan", ""},
 	{MOUSEZOOM, "TRACKPADZOOM", 0, "Mouse/Trackpad Zoom", ""},
 	{MOUSEROTATE, "MOUSEROTATE", 0, "Mouse/Trackpad Rotate", ""},

source/blender/windowmanager/intern/wm_event_system.c

@@ -1614,7 +1614,7 @@ void wm_event_do_handlers(bContext *C)
 		while( (event= win->queue.first) ) {
 			int action = WM_HANDLER_CONTINUE;
 
-			if((G.f & G_DEBUG) && event && event->type!=MOUSEMOVE)
+			if((G.f & G_DEBUG) && event && !ELEM(event->type, MOUSEMOVE, INBETWEEN_MOUSEMOVE))
 				printf("pass on evt %d val %d\n", event->type, event->val); 
 			
 			wm_eventemulation(event);
@@ -2138,6 +2138,7 @@ void wm_event_add_ghostevent(wmWindowManager *wm, wmWindow *win, int type, int t
 		case GHOST_kEventCursorMove: {
 			if(win->active) {
 				GHOST_TEventCursorData *cd= customdata;
+				wmEvent *lastevent= win->queue.last;
 				
 #if defined(__APPLE__) && defined(GHOST_COCOA)
 				//Cocoa already uses coordinates with y=0 at bottom, and returns inwindow coordinates on mouse moved event
@@ -2156,6 +2157,12 @@ void wm_event_add_ghostevent(wmWindowManager *wm, wmWindow *win, int type, int t
 
 				event.type= MOUSEMOVE;
 
+				/* some painting operators want accurate mouse events, they can
+				   handle inbetween mouse move moves, others can happily ignore
+				   them for better performance */
+				if(lastevent && lastevent->type == MOUSEMOVE)
+					lastevent->type = INBETWEEN_MOUSEMOVE;
+
 				update_tablet_data(win, &event);
 				wm_event_add(win, &event);
 				

source/blender/windowmanager/wm_event_types.h

@@ -70,6 +70,7 @@
 		/* mapped with userdef */
 #define WHEELINMOUSE	0x00c
 #define WHEELOUTMOUSE	0x00d
+#define INBETWEEN_MOUSEMOVE	0x011
 
 
 /* SYSTEM : 0x01xx */