[FIXED] Pyside program locks up in response to a checkbox click

Issue

I am having a very strange problem. Whenever the QCheckBox is checked it calls drawall as expected. However when drawall is finished it completely hangs. I have tried directly calling drawall (Version 2) when clicked but with no luck the result is the same.

scene = QGraphicsScene(0, 0, 500, 500)

class SurrogateBeat(QGraphicsItem):
    def __init__(self,beat,top):
        super(SurrogateBeat, self).__init__()
        print "Init"

class Test(QWidget):
    def __init__(self):
        self.drawAll = QCheckBox("Draw all frames on screen",self)
        self.drawAll.stateChanged.connect(self.onDrawAllClicked)

    def onDrawAllClicked(self):                #Version 1
        QTimer.singleShot(0, self.drawall)

    def onDrawAllClicked(self):                #Version 2 (neither work)
        self.drawall()

    def drawall(self):
        if self.drawAll.checkState() ==  Qt.CheckState.Checked: 
            self.surrogates=[]
            for b in range(0,len(self.item.beats)):
                print "Loop"
                surrogate = SurrogateBeat(b, self.item)
                scene.addItem(surrogate)
                self.surrogates.append(surrogate)
            scene.update()
            print "Update"

Loop prints out 16 times, the init for SurrogateBeat prints out so it is being called, but after "Update" prints out, the program is hung.

Solution

QGraphicsItem is an abstract base class.

As a minimum, your SurrogateBeat subclass will need to reimplement the boundingRect and paint functions.

Answered By - ekhumoro