Arabic/Persian text is trimmed on almost all widgets

Almost all texts on QLabel, QCheckBox, QRadiobox and QTabWidget are trimmed in both sides. There must be something wrong with the code that calculates width of text for Arabic chars given a specific font.

I tried several fonts; same result. I seems that longer the text is, more characters are trimmed.

Currently I'm adding one or two spaces before and after each title on every widget in my app as a temporary workaround which is very annoying.

I made a simple example to demonstrate the difference.