Question

My problem is I want to keep rotating the scene if the checkbox is checked, and stop this rotation immediately once it is unchecked. However, “keep rotating” means an infinite loop…

So after entering the loop, the program gets kind of freezed and no longer react to my “uncheck” signal. Is there a way to interrupt this loop? The following is skeleton of related code.
Thanks!

class Draw(QGLWidget):    
    def __init__(...):
        ...
        self.rotate=0
        self.auto=False

    def paintGL(self):
        glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
        glLoadIdentity()

        glRotatef(self.rotate,0.0,0.0,1.0)
        draw stuff...

        glFlush()

    def autoRotate(self,auto): # auto is an integer and used here as true/false 
        self.auto=auto
        while self.auto:
            self.rotate+=0.5
            if self.rotate>360:
                self.rotate-=360
            self.updateGL()
            if auto==False:
                break


class SpiralWidgetDemo(QtGui.QMainWindow):
    def __init__(self):
       ...
       auto=QtGui.QCheckBox("Auto")
       self.connect(auto,QtCore.SIGNAL("stateChanged(int)"),widget.autoRotate)

Answer 1

You must not implement this as a loop. This is defined to break the interaction of the program, as it prevents the “main loop” of the Qt application from running.

Put your drawing code into an event handler (like redraw event), and use a timer to generate events at regular intervals (e.g. 10/s).