Use a minimal expression context in symbol layer tree preview icons

Allows the preview icon to correctly show linked project colors (cherry picked from commit 3c0c253)
qgis · Jan 17, 2019 · 387334d · 387334d
1 parent 4d54a1f
commit 387334d
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/src/core/symbology/qgssymbollayerutils.cpp b/src/core/symbology/qgssymbollayerutils.cpp
@@ -730,6 +730,11 @@ QIcon QgsSymbolLayerUtils::symbolLayerPreviewIcon( QgsSymbolLayer *layer, QgsUni
   painter.begin( &pixmap );
   painter.setRenderHint( QPainter::Antialiasing );
   QgsRenderContext renderContext = QgsRenderContext::fromQPainter( &painter );
+  // build a minimal expression context
+  QgsExpressionContext expContext;
+  expContext.appendScopes( QgsExpressionContextUtils::globalProjectLayerScopes( nullptr ) );
+  renderContext.setExpressionContext( expContext );
+
   QgsSymbolRenderContext symbolContext( renderContext, u, 1.0, false, nullptr, nullptr, QgsFields(), scale );
   layer->drawPreviewIcon( symbolContext, size );
   painter.end();