[Qgis-developer] Incremental rendering update

Hugentobler Marco marco.hugentobler at karto.baug.ethz.ch
Wed Oct 17 06:51:23 EDT 2007

Hi Tim,

That would be great!


-----Ursprüngliche Nachricht-----
Von: Tim Sutton [mailto:tim at linfiniti.com]
Gesendet: Mi 17.10.2007 12:24
An: Martin Dobias
Cc: Hugentobler  Marco; qgis-developer at lists.qgis.org
Betreff: Re: [Qgis-developer] Incremental rendering update

Ill test the patch on mac and see if it presents any issues with
processEvents() calls.



2007/10/16, Martin Dobias <wonder.sk at gmail.com>:
> On 10/16/07, Hugentobler  Marco <marco.hugentobler at karto.baug.ethz.ch> wrote:
> > Hi Martin,
> >
> > Here it is:
> >
> > http://karlinapp.ethz.ch/qgis_incremental_update.diff
> Hi Marco,
> I've took a look at the code and tested a bit, here are my notes:
> - I remember that after Qt4 port Tom disabled processEvents() calls
> during the rendering due because they were producing UI problems and
> even crashes... now it seems that it works again (Qt4.2.3 here) - or
> did you have to do something special to avoid those troubles?
> - I've noticed you've disabled usage of QPixmap in QgsMapCanvasMap ...
> was there any particular reason for that or just because of being a
> proof of concept?
> - the usual purpose of layer's repaintRequested signal is different -
> it's emitted when the layer thinks it should be re-rendered, while you
> use it to signal that there is some progress in drawing...
> - if I understand it correctly, QgsMapCanvas::refresh() has changed
> its semantics from being trigger of rendering to just being updater of
> the drawn map. Some of the refresh() calls have been changed to
> drawIncrementally() and some not, which produces some bugs when
> working with the map canvas. (wouldn't it be better to preserve
> original meaning of refresh() function?)
> - raster layers could also do some updates during rendering...
> - an important thing what's missing so far is lack of mechanism which
> would stop rendering - e.g. when you hit escape key or when you move
> the map it should stop   and start rendering again
> But after all I'm happy to see that we can allow some level of
> concurrency while rendering even without the need to use threading...
> Nice work!
> Martin
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Tim Sutton
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