Incorrect drawing QTextDocument with negative rigthBearing

Hello!
There is a problem with rendering QTextDocument in our project.
We develop CAD system, which is used very widely in the Russia "GOST type A" font. And with him have problems when rendering using QTextDocument.

I prepared a test application and examples of his work:

• gost.png - correctly drawing one char without italic style.
• gost_italic.png - incorrect drawing one char with italic style.
• arial.png - same behaviour as gost_italic but with more popular "Arial" font.

Based on analysis of these data, I concluded that the incorrect behavior begins when rightBearing of char have a negative value.

As I understand, QTextEdit use same drawing engine and it is also affected by this problem (see attachment qtextedit.png).

Can you make some investigation and confirm this bug?