Canvas problems

[Tommytrojan]

Hi,

I'm having problems with an application that uses the QCanvasView. My canvas items get distorted if another window covers them and then SLOWLY uncovers the items. This is especially pronounced when the view is zoomed. I created a minimal application that exhibits the problem (I'm using PyQt but you should be able to reproduce it with C++). I have also attached a screen shot of what I get when I move another window across my application. I have a feeling this is related to rounding errors of the world matrix transformation. Although I occasionally see these kind of problem when there is no transformation matrix involved.
Maybe this has been fixed in a later version. I'm using Qt 3.3.1 on a Windows XP box.
Please let me know if you can't reproduce this effect with a newer version.

Thanks,
Thomas

import sys
import qt
import qtcanvas
 
class TMainWindow(qtcanvas.QCanvasView):
  def __init__(self, *args):
    qtcanvas.QCanvasView.__init__(self, *args)
 
    oMatrix = qt.QWMatrix()
    oMatrix.scale(2, 2)
    self.setWorldMatrix(oMatrix)
    oRect = qtcanvas.QCanvasRectangle(20, 50, 100, 100, self.canvas())
    oRect.setBrush(qt.QBrush(qt.QColor('red')))
    oRect.show()
 
  def closeEvent(self, e):
    oApp.quit()
 
oApp = qt.QApplication(sys.argv)
canvas = qtcanvas.QCanvas(2000, 2000)
oMainWindow = TMainWindow(canvas, None, 'Main Window')
oMainWindow.show()
oApp.exec_loop()

import sys
import qt
import qtcanvas

class TMainWindow(qtcanvas.QCanvasView):
  def __init__(self, *args):
    qtcanvas.QCanvasView.__init__(self, *args)

    oMatrix = qt.QWMatrix()
    oMatrix.scale(2, 2)
    self.setWorldMatrix(oMatrix)
    oRect = qtcanvas.QCanvasRectangle(20, 50, 100, 100, self.canvas())
    oRect.setBrush(qt.QBrush(qt.QColor('red')))
    oRect.show()
    
  def closeEvent(self, e):
    oApp.quit()
    
oApp = qt.QApplication(sys.argv)
canvas = qtcanvas.QCanvas(2000, 2000)
oMainWindow = TMainWindow(canvas, None, 'Main Window')
oMainWindow.show()
oApp.exec_loop()

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