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  1. Qt
  2. QTBUG-16932

Rendering errors on QGraphicsView with OpenVG paint engine (at least on Symbian)



    • Type: Bug
    • Status: Closed
    • Priority: P1: Critical
    • Resolution: Done
    • Affects Version/s: 4.6.3, 4.7.1
    • Fix Version/s: 4.7.2
    • Labels:
    • Environment:
      Symbian^3 - tested on N8
    • Commits:


      Multiple (small rotated)* items that start in the same location and move apart cause a horrible visual effect (spreading trail of black bounding boxes).

      Root cause uncertain but seems to be related to the items initially overlapping?

      Small test app to reproduce this attached. Setting the paint engine to "raster" resolves this (although with some occasional flickering black boxes - probably due to lack of sync on the updates) although of course is not a viable workaround!

      Oddly, starting the app from the IDE with the screensaver running makes the issue much better, although not entirely fixed (some bits of the objects get left behind), when you then exit the screensaver while it's running. Suggests some problem with the state of the hardware accelerator? (I have the "Big Clock" screensaver active - not experimented with others).

      I have experimented with item cache modes without any success.

      The example uses QGraphicsRectItems but the same occurs with QGraphicsPixmapItems.

      Please, please resolve this for the final 4.7 release for Symbian - it makes a bunch of 2D games effects on graphics view completely unusable!

      • According to my experiments neither of these factors is relevant but that's what the test app does because I've just pulled an explosion effect out of the game I'm porting.

      N.B. The test app runs in a loop and has no exit button - you have to kill it from the IDE or the task manager on the device.


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            jhautaka Jani Hautakangas
            m_p_wilcox Mark Wilcox
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