QPainter not active



  • Hello,

    I am making a simple program in Python with PyQT 5 for GUI, which is supposed to draw a square onto the screen.

    However, I am quite confused as to how I am supposed to set up my QPainter.

    I have the following code:

    from PyQt5 import QtWidgets, QtGui, QtCore
    import sys
    
    def paintEvent(self, x, y, color, event = None):
        global qp
        qp = QtGui.QPainter(self);
        qp.begin(self)
        qp.setPen(QtGui.QColor(int(color, 16)))
        qp.setBrush(QtGui.QColor(int(color, 16)))
        qp.drawRect(x, y, 25, 25)
        qp.end()
    
    def window(title, width, height):
        app = QtWidgets.QApplication(sys.argv)
        w = QtWidgets.QWidget()
        w.setFixedSize(width, height)
        w.setWindowTitle(title)
        paintEvent(w, 0, 0, 'ffffff')
        w.show()
        sys.exit(app.exec_())
    
    window('test', 120, 120)
    

    But this gives me:

    QWidget::paintEngine: Should no longer be called
    QPainter::begin: Paint device returned engine == 0, type: 1
    QWidget::paintEngine: Should no longer be called
    QPainter::begin: Paint device returned engine == 0, type: 1
    QPainter::setPen: Painter not active
    QPainter::setBrush: Painter not active
    QPainter::drawRects: Painter not active
    QPainter::end: Painter not active, aborted
    

    Can someone point me in the right direction?

    Thanks,
    Matt

    P.S First post. new to Qt - don't be harsh ;)


  • Lifetime Qt Champion

    Hi and welcome to devnet,

    If you want to do custom painting, you have to create a custom QWidget subclass and reimplement the paintEvent method of that class. You can't just freely paint from anywhere at any time.



  • I don't quite know how to do that, could you expand on that, please?


  • Lifetime Qt Champion

    A quick google search returns this article which covers most aspects of this subject.


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