[Qgis-developer] WMS Design Problem and Mac Crash

[Marco Hugentobler]

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).

cheers,
Marco 

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