[Qgis-developer] Rendering cache and labeling

Hugo Mercier hugo.mercier at oslandia.com
Fri Dec 19 00:32:38 PST 2014

Hi Martin,

Le 19/12/2014 09:26, Martin Dobias a écrit :
> Hi Hugo
> On Wed, Dec 17, 2014 at 10:28 PM, Hugo Mercier
> <hugo.mercier at oslandia.com <mailto:hugo.mercier at oslandia.com>> wrote:
>     Hi,
>     When labeling is enabled on a layer, then the rendering cache is made
>     invalid and everything is computed for rendering.
>     I may be missing something obvious, but I don't understand why.
>     Is it because of a particular use case or because of some limitations in
>     the caching process ?
> If we used cached layer image, the features for labeling from that layer
> would not be registered and therefore they would not appear. A smarter
> solution would be to keep the layer cached and just iterate over layer's
> features to register them (if they would get rendered).

Thanks for your answer.

But, I'm not sure to follow :)

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 ?

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