[QGIS-Developer] [PyQGIS] Unexpected crash using: QgsFeatureRenderer.symbolForFeature()

[Benjamin Jakimow]

Hi Janvier,

maybee you need to use it within a startRender and stopRender section:

renderContext = QgsRenderContext()
renderContext.setExtent(layer.extent())
renderer = layer.renderer().clone()
renderer.startRender(renderContext, layer.fields())
features = layer.getFeatures(fids)
for i, featurein enumerate(features):
     symbol = renderer.symbolForFeature(feature, renderContext)
     # ... renderer.stopRender(renderContext)

Greetings, Benjamin

Am 04/03/2021 um 11:46 schrieb Janvier Thomas:
>
> Hi,
>
>
> I got an issue with SIP python bindings…
> I’m looking to loop over QgsVectorLayer features to convert geometries 
> to mesh primitives (cells) …
>
> I had a first problem with the non-const (unexpected crash about SIP 
> methods)
> |for part in feature.geometry().parts():|
> that I solved using the const one
> |for p in f.geometry().constParts():|
>
> ||
>
> But now I’m facing a similar crash when trying to identify the 
> symbol/category/legendKey of each feature
> (the aim is to add the legendKey as a cell attribute to link color/LUT 
> between the mesh and vectorlayer)
>
> I do it this way:
> layer.renderer().symbolForFeature(feature, context)
>
> But ends up with a :
>
> Crash ID: cb1c4f2b11cbd392a38c522a5ed1e194e060e4a0
>
> Stack Trace
>
> QgsExpression::evaluate :
>
> QgsCategorizedSymbolRenderer::valueForFeature :
>
> QgsCategorizedSymbolRenderer::originalSymbolForFeature :
>
> PyInit__core :
>
> PyMethodDef_RawFastCallKeywords :
>
> PyMethodDef_RawFastCallKeywords :
>
> PyEval_EvalFrameDefault :
>
> PyEval_EvalCodeWithName :
>
> I opened an Issue here (not sure this is relevant):
> Unexpected crash using: QgsFeatureRenderer.symbolForFeature() · Issue 
> #68 · qgis/pyqgis (github.com) <https://github.com/qgis/pyqgis/issues/68>
>
> Thanks a lot
>
>
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-- 
Benjamin Jakimow, Doctoral Researcher
Earth Observation Lab | Geography Department | Humboldt-Universität zu Berlin

e-mail: benjamin.jakimow at geo.hu-berlin.de

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