[Qgis-developer] WMS Design Problem and Mac Crash
tim at linfiniti.com
Mon Feb 12 13:46:19 EST 2007
2007/2/12, Marco Hugentobler <marco.hugentobler at karto.baug.ethz.ch>:
> And this composition manager could render a scene in QGIS in tiles such that
> the progress is better visible for users. If the system is idle, it could
> render the tiles around the visible area such that pan actions in the future
> are very fast (also see google & co. for an example).
Yes..of course there will be a couple of gotchas like making sure that
labelling behaves well when rendered across tile boundaries etc...
> Am Sonntag, 11. Februar 2007 12:30 schrieb Tim Sutton:
> > Hi
> > I support this idea. In fact it might work well with and idea I had
> > some time ago for creating a caching and composition manager for QGIS.
> > The idea being that when a scene is rendered and the extents havent
> > changed (e.g. one layers visibility was toggled) the compoistion
> > manager renders the layers directly from the cached copy rather then
> > redrawing every aspect of the scene. In addition to that we can gain
> > on performance by not rendering part of the scene that were rendered
> > in the last draw event. For example if the user pans, we can just
> > fetch the new area of the scene and stitch it onto the still visible
> > parts of the last scene. For things like WMS I think this could
> > provide an especially good performance benefit. Also for network
> > intensive layers like PostGIS it should provide some benifit. Letting
> > the user allocate a certain amount of memory (or disk space like
> > google earth does), we could in fact store numerous previously
> > rendered layers scenes and pull them straight from disk. If course we
> > would need to flush the cache for a layer if its symbology changes
> > etc.
> > So adding loadImage() to the mapLayer interface would be a good first
> > step in that direction.
> > Regards
> > Tim
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