Forgot to add to log of previous commit:

The purpose was to set a wait-cursor draw on 3d windows. I tried for
but it keeps failing... inside threads you can't do UI stuff. Needs
further thinking, probably something via jobs system.

source/blender/editors/render/render_internal.c

@@ -642,6 +642,7 @@ static int render_breakjob(void *rjv)
 static void render_drawlock(void *UNUSED(rjv), int lock)
 {
 	BKE_spacedata_draw_locks(lock);
+	
 }
 
 /* catch esc */