[PyQt] Drawing on a QFrame

[Phil]

On 28/06/13 18:56, Phil Thompson wrote:
> On Fri, 28 Jun 2013 15:35:20 +1000, Phil <phil_lor at bigpond.com> wrote:
>> Thank you for reading this.
>>
>> I'd like to draw on a QFrame.
>>
>> The following does draw a line but not on the frame, instead the line is
>
>> drawn on the main window.
>>
>> I've done this years ago with Qt and C++ but I don't remember how I did
> it.
>>
>> class DrawTest(QtGui.QMainWindow):
>>       def __init__(self, parent=None):
>>           super(DrawTest, self).__init__(parent)
>>           self.ui = Ui_MainWindow()
>>           self.ui.setupUi(self)
>>           frame = QtGui.QFrame()
>>
>>       def paintEvent(frame, event):
>>           qp = QtGui.QPainter()
>>           qp.begin(frame)
>>           pen = QtGui.QPen(QtCore.Qt.yellow, 4)
>>           qp.setPen(pen)
>>           frame.drawLine(event, qp)
>>           qp.end()
>>
>>       def drawLine(frame, event, qp):
>>           qp.drawLine(10, 10, 30, 30)
>
> Sub-class the frame and reimplement its paintEvent(). Also make sure the
> frame isn't being garbage collected (like it is above) and add it to the
> GUI somewhere.
>

Thank you Rob and Phil,

It's still not totally clear to me. Say for example, that I want to 
display a frame on the main window and draw a red line on the frame and, 
through another function, draw a yellow line on the main window.

I've added the extra class as Rob has suggested but I'm not getting the 
result that I expect. The Frame class would be a separate module but 
I've put the two classes in the same module for this example.

class DrawTest(QtGui.QMainWindow):
     def __init__(self, parent=None):
         super(DrawTest, self).__init__(parent)

If I comment out the following two lines then I get a red line on the 
frame but only the frame is displayed without the main window.

	self.ui = Ui_MainWindow()
         self.ui.setupUi(self)

If I comment out the following two lines then, of course, I'm back to 
where I started with a yellow line on the main window and the empty 
frame is displayed.

         self.frame = Frame(self)
         self.setCentralWidget(self.frame)

     def buttonClicked(self):
         print("clicked")

     def paintEvent(self, event):
         qp = QtGui.QPainter()
         qp.begin(self)
         pen = QtGui.QPen(QtCore.Qt.yellow, 4)
         qp.setPen(pen)
         self.drawLine(event, qp)
         qp.end()

     def drawLine(self, event, qp):
         qp.drawLine(10, 10, 30, 30)

class Frame(QtGui.QFrame):
     def paintEvent(self, event):
         qp = QtGui.QPainter(self)
         qp.setPen(QtGui.QPen(QtCore.Qt.red, 4))
         qp.drawLine(10,10,30,30)

if __name__ == "__main__":
     app = QtGui.QApplication(sys.argv)
     mySW = DrawTest()
     mySW.show()
     sys.exit(app.exec_())


-- 
Regards,
Phil