[Qgis-developer] highlighting features

[Vincent Mora]

Hi,

I'm working on issue 4819 and noticed that when a feature is selected,
the pan is fast even with complex polygons whereas the pan slows down a
lot when features are highlighted.

My best guesses for the difference is:
1) pan operation use cached image for rendering in rendereV2
2) rendering style and/or pipeline is sufficiently different to cause
delays (this would explain why refresh after pan drag/drop takes 4sec
with highlighted feature, while cached image refresh takes only 2sec
otherwise)

The fix I can think about for this are either:
1) to introduce caching in QgsHighlight (therefore adding substantial
complexity to this class).
2) to add the parameter "highlighted" (along with "selected") to
QgsFeatureRendererV2::renderFeature and get rid of QgsHighlight
altogether (or at least deprecate it).

What is the best option: caching in QgsHighlight, modifying
renderFeature, or something I did not think about ?
 
Thanks,

V.