The difference between QPinter and QPaintEvent

Hi!
When I use QPainter. Should I use the QPaintEvent with QPainter?
thanks.

Quote:

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When I use QPainter

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When you want to paint something on a paint device:

Code:

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QImage image("picture.jpg");
QPainter painter(&image);
painter.drawLine(0,0,image.width(),image.height());
// draw a diagonal line on an image

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QPainter can be used on images, printers and widgets (and few other things derived from QPaintDevice).
QPaintEvent is an event - it is sent to a widget that needs to update itself. It contains some parameters related to the area being repainted;
Typically you reimplement a "paintEvent" protected method in a class derived from QWidget:

Code:

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class MyWidget : public QWidget{
Q_OBJECT
protected:
    void paintEvent(QPaintEvent * event){
        QPainter painter(this);
        //... now you can draw something on current widget
    }
};

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When it comes to QWidgets, QPainter can be used only inside of paintEvent() method.

Quote:

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The difference between QPinter and QPaintEvent

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QPainter is an object used to draw stuff on various paint devices (not necessarily widgets), whereas QPaintEvent is an event related to rendering on QWidgets and Qt event system.