[Qgis-developer] How to change layer without redrawing the whole map

[Kanwar, Jonny]

Dear all,

We would like to write a Qgis plugin (either C++ or python, doesn't
matter) that allows us to visualize movements of vehicles over time.
Suppose the plugin provides coordinates for each second and vehicle. Our
fear is that for each frame to be rendered the whole map is redrawn. Do
you see a way to enable Qgis to only update the animated layer and not
all layers at once?

We know there is the time manager plugin that provides capabilities
similar to our requests. However, at our tests, this plugin suffered of
poor performance.

To get a bit more technical: As far as I understand the QgsMapCanvas has
to be redrawn as soon as a single element of one of the layers changes.
Is there a way to add some overlay that is just merged with the other
(already rendered) image?

Thanks for your support.

Jonny Kanwar


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