Bugfix #25422

In some cases the User Preferences UI was "vibrating" on redraws.
Could only be redone by some, but this fix is confirmed to work.

source/blender/editors/space_userpref/space_userpref.c

@@ -49,6 +49,8 @@
 #include "WM_api.h"
 #include "WM_types.h"
 
+#include "UI_view2d.h"
+
 #include "userpref_intern.h"	// own include
 
 /* ******************** default callbacks for userpref space ***************** */
@@ -110,6 +112,9 @@ static void userpref_main_area_init(wmWindowManager *wm, ARegion *ar)
 
 static void userpref_main_area_draw(const bContext *C, ARegion *ar)
 {
+	/* this solves "vibrating UI" bug #25422 */
+	UI_view2d_region_reinit(&ar->v2d, V2D_COMMONVIEW_PANELS_UI, ar->winx, ar->winy);
+	
 	ED_region_panels(C, ar, 1, NULL, -1);
 }