passing a QPainter object to widgets

[mcosta]

So the problem is probably because you create a copy that QPainter.

Qt Official Documentation says

QPainter::QPainter ( QPaintDevice * pd )
Constructs a painter that begins painting the paint device pd immediately.
This constructor is convenient for short-lived painters, e.g. in a paint event and should be used only once.

The constructor calls begin() for you and the QPainter destructor automatically calls end().

So, you must use QPainter pointer.

[vratojr]

You were right, I resolved doing that way.

Thank you very much boys!