[Qgis-developer] Patch for screen updates during long rendering operations

Marco Hugentobler marco.hugentobler at karto.baug.ethz.ch
Sat Dec 22 06:06:42 EST 2007

The problem on Mac seems to be the flag Qt::excludeUserInputEvents. Obviously, 
the resize event is a user input event on Mac, but not on Win and Linux :-)

Please test this new patch, it works for me also on Mac. As 
QApplication->processEvents() is used now instead 
QApplication->processEvents(Qt::excludeUserInputEvents), some queries have 
been added to prevent users from adding layers, removing layers, zooming, 
etc. while the drawing is in progress.


On Sunday 16 December 2007 06:48:02 Tom Elwertowski wrote:
> Hi Marco,
> The WMS resize optimization doesn't work on a Mac. When I resize a WMS
> layer, the image is repeatedly fetched and the window slowly grows by
> one pixel increments. The problem doesn't happen on Ubuntu. When I
> resize the same layer there, the intermediate redraws are skipped.
> One improvement is that newer redraws no longer interrupt the draw in
> progress so the screen corruption during resizing is gone.
> I will look for the cause of the extra redraws sometime in the next few
> days.
> Another difference is that if I maximize the window on a Mac with
> incremental update enabled, the window resize does not happen until
> after the redraw. First the map view grows and the maximized map is
> incrementally rendered while the full view is not visible. Only at the
> end does the window expand and the map becomes fully visible without
> additional redrawing. On Ubuntu, it works more as expected. The window
> expands first and then the map is incrementally rendered into the
> enlarged and fully visible view.
> Tom

Dr. Marco Hugentobler
Institute of Cartography
ETH Zurich
Technical Advisor QGIS Project Steering Committee
marco.hugentobler at karto.baug.ethz.ch
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