AW: AW: [Qgis-developer] Addition to QgsRenderContext

Hugentobler Marco marco.hugentobler at
Wed Aug 5 01:22:22 EDT 2009

Hi Magnus

>1) Set alpha channel dynamically, or
>2) Cache in QgsVectorLayer

What do you mean with 'set alpha channel dynamically'?

Adding an extra parameter to the interfaces, as you suggested, sounds reasonable to me. Keep attention to add default values for it in the function signatures (to not break API compatibility for plugins and third party applications).


-----Ursprüngliche Nachricht-----
Von: qgis-developer-bounces at im Auftrag von Magnus Homann
Gesendet: Di 04.08.2009 21:22
An: qgis-developer
Betreff: Re: AW: [Qgis-developer] Addition to QgsRenderContext
Hugentobler Marco skrev:
> Hi Magnus
> How would you add the transparency to the render context?
> The rendercontext is meant to contain information about the rendering procedure as a whole (so not information that is layer or even symbol specific).

Thanks, I probably misunderstood the purpose of the render context.

Yes, the cache stores transparency, but to send the wanted transprancey down from QgsVectorLayer through QgsRenderer to QgsSymbol requiers an extra parameter in the interfaces. Maybe that's the best way?

Well, if we want to keep it within Qgsvectorlayer, we could:
1) Set alpha channel dynamically, or
2) Cache in QgsVectorLayer

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