[Qgis-developer] Rendering cache and labeling

Martin Dobias wonder.sk at gmail.com
Fri Dec 19 00:42:01 PST 2014


On Fri, Dec 19, 2014 at 3:32 PM, Hugo Mercier <hugo.mercier at oslandia.com>
wrote:
>
>
> Suppose I have an uncached layer with labeling switched on.
> During the first rendering, everything is drawn, including labels.
> During the second rendering (same extent), the cache could be reused and
> it would include labels previously drawn during the first rendering. No ?
>

No... the labeling is not cached anywhere. Therefore in every rendering job
it is necessary to register all features that may have labels again in
order to be considered in the labeling.

Also think about this case: there is one layer with labeling, it gets
cached. Then user adds another layer with labels - it is necessary to
recalculate the labeling again as the new layer may require some existing
labels to be hidden or moved to a different position to fit labels from the
new layer. Hopefully that makes sense :-)

Cheers
Martin
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