scale painter to fit my widget

[jesse_mark]

by looking into setWindow and setViewPort,

I understood that by setWindow i can tell the painter the rect i want it to draw in it.
so i did this :

QRect widgetRect = this->rect();
QRect windowRect; 
 
windowRect.setHeight(widgetRect.height()-50);
windowRect.setWidth(widgetRect.width()-50);
windowRect.setX(widgetRect.x()-50);
windowRect.setY(widgetRect.y()-50); 
 
 painter.setWindow(windowRect); 
painter.drawRect(myRect);

QRect widgetRect = this->rect();
QRect windowRect; 

windowRect.setHeight(widgetRect.height()-50);
windowRect.setWidth(widgetRect.width()-50);
windowRect.setX(widgetRect.x()-50);
windowRect.setY(widgetRect.y()-50); 

 painter.setWindow(windowRect); 
painter.drawRect(myRect);

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expecting that when i draw using the painter it will draw inside this windowRect.

but it does not, it will draw out of the border in the invisable area for the user.

I dont know what exactlly i should set it.