Arabic text is clipped in QLabel, and QGroupBox, and QTabWidget

when writing arabic text in QLabel and setting Horizontal Size policy to Maximum ( or use a horizontal spacer besides the control) the text is clipped !

as far as I have checked, it usually happen when a text ending with "ص" or "ل" or "ف" .

sometimes that happens with English text as well, but I can't remember how.

Attacked screen shots of the problem, and the sample code I wrote to demonstrate the problem.

Edit 1:
I tried to trace the problem, looks like QFontMetrics.width(), and boundingRect() returns wrong width for the given arabic text. the values are less than the values returned from those methods back in Qt 5.2 and lower versions.