QPainter save() and restore()

[babu198649]

hi
i am doing only one operation inside paintEvent(QPainter::drawPixmap()) ,is it necessary to use save() and restore() .

[wysota]

No, of course not, Qt guards the painter state itself before calling your code, so all the changes to the painter will be restored after the paint event of yours is left.

[babu198649]

If i do a series of operations inside a paintEvent(pixmap painting,draw lines,e.t.c),then is it necessary to use save() and restore().

[salmanmanekia]

If you perform one operation at a time and require the same operation sometime later then save it and restore it later ...:)

[jpn]

You will instantiate a different QPainter object on the stack during every paintEvent() anyway so saving and restoring doesn't make sense unless you really need to get back to some earlier state. Drawing a line doesn't change the state of a QPainter object, but for example setting a pen before drawing the line does. QPainter docs contain a list of settings (http://doc.trolltech.com/4.4/qpainter.html#settings) what are saved and restored.