Rotate UIWidget does not update display

[hesoul]

I have a issue,when I rotate widget around the axis(1,1,0) or (-1,-1,0),the widget does not update display.
I found the function [UIWidget.UpdateTransform] only determine whether the bottom-left and upper-right corner to move,
so if you rotate widget around the axis which through those two points,will not update display.
how to fix it? determine three or four point?

[ArenMook]

MarkAsChanged() on the widget forces its flag.