[QGIS-Developer] QGIS3: Python QgsFeatureRenderer subclass problem

[Chris Crook]

Continued: Ok, understand a bit more now.  Still not sure where the clone should be created but if the same renderer is called from more than one thread, as the first time startRender is called it sets the thread id for the rendererer, and thereafter cannot be called with a different thread id.  So issue could either be if startRender does not invoke super.startRender (to set thread id) or if called from two threads.
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From: QGIS-Developer [qgis-developer-bounces at lists.osgeo.org] on behalf of Chris Crook
Sent: 08 February 2018 08:45
To: qgis-developer at lists.osgeo.org
Subject: [QGIS-Developer] QGIS3: Python QgsFeatureRenderer subclass problem

I am converting a python  plugin the implements a subclass of QgsFeatureRenderer.  At the moment the plugin is dying on the startRender function with the message (from the base class)

"ASSERT failure in QgsFeatureRenderer::renderFeature: \"renderFeature called in a different thread - use a cloned renderer instead\"

I can't see where I should be creating the cloned renderer for the rendering.  I had a look at the QgsSingleSymbolRenderer C++ code and I can't see anything there, so I'm wondering if the python implementation in some way corrupts the multiprocessing implementation.  Can anyone offer any suggestions

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