QgsRendererRasterPropertiesWidget's syncToLayer takes care of not

overwriting existing QgsRasterRenderers with a default renderer modified test_qgsrendererrasterpropertieswidget.py to check if an existing band-number > 1 is used to update the render widget fixes #34602
qgis · Oct 29, 2021 · 289f540 · 289f540
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Showing 2 changed files with 17 additions and 12 deletions.
diff --git a/src/gui/raster/qgsrendererrasterpropertieswidget.cpp b/src/gui/raster/qgsrendererrasterpropertieswidget.cpp
@@ -296,16 +296,21 @@ void QgsRendererRasterPropertiesWidget::setRendererWidget( const QString &render
       const QgsRectangle myExtent = mMapCanvas->mapSettings().outputExtentToLayerExtent( mRasterLayer, mMapCanvas->extent() );
       if ( oldWidget )
       {
-        if ( rendererName == QLatin1String( "singlebandgray" ) )
-        {
-          whileBlocking( mRasterLayer )->setRenderer( QgsApplication::rasterRendererRegistry()->defaultRendererForDrawingStyle( QgsRaster::SingleBandGray, mRasterLayer->dataProvider() ) );
-          whileBlocking( mRasterLayer )->setDefaultContrastEnhancement();
-        }
-        else if ( rendererName == QLatin1String( "multibandcolor" ) )
+        QgsRasterRenderer *oldRenderer = oldWidget->renderer();
+        if (!oldRenderer || oldRenderer->type() != rendererName)
         {
-          whileBlocking( mRasterLayer )->setRenderer( QgsApplication::rasterRendererRegistry()->defaultRendererForDrawingStyle( QgsRaster::MultiBandColor, mRasterLayer->dataProvider() ) );
-          whileBlocking( mRasterLayer )->setDefaultContrastEnhancement();
+            if ( rendererName == QLatin1String( "singlebandgray" ) )
+            {
+              whileBlocking( mRasterLayer )->setRenderer( QgsApplication::rasterRendererRegistry()->defaultRendererForDrawingStyle( QgsRaster::SingleBandGray, mRasterLayer->dataProvider() ) );
+              whileBlocking( mRasterLayer )->setDefaultContrastEnhancement();
+            }
+            else if ( rendererName == QLatin1String( "multibandcolor" ) )
+            {
+              whileBlocking( mRasterLayer )->setRenderer( QgsApplication::rasterRendererRegistry()->defaultRendererForDrawingStyle( QgsRaster::MultiBandColor, mRasterLayer->dataProvider() ) );
+              whileBlocking( mRasterLayer )->setDefaultContrastEnhancement();
+            }
         }
+        delete oldRenderer;
       }
       mRasterLayer->renderer()->setAlphaBand( alphaBand );
       mRasterLayer->renderer()->setOpacity( opacity );

diff --git a/tests/src/python/test_qgsrendererrasterpropertieswidget.py b/tests/src/python/test_qgsrendererrasterpropertieswidget.py
@@ -30,14 +30,14 @@ def multibandRasterLayer(self) -> QgsRasterLayer:
     def test_syncToLayer_SingleBandGray(self):
 
         lyr = self.multibandRasterLayer()
-        lyr.setRenderer(QgsSingleBandGrayRenderer(lyr.dataProvider(), 1))
+        lyr.setRenderer(QgsSingleBandGrayRenderer(lyr.dataProvider(), 2))
         c = QgsMapCanvas()
         w = QgsRendererRasterPropertiesWidget(lyr, c)
         assert isinstance(w.currentRenderWidget().renderer(), QgsSingleBandGrayRenderer)
-        assert w.currentRenderWidget().renderer().grayBand() == 1
-        lyr.renderer().setGrayBand(2)
-        w.syncToLayer(lyr)
         assert w.currentRenderWidget().renderer().grayBand() == 2
+        lyr.renderer().setGrayBand(1)
+        w.syncToLayer(lyr)
+        assert w.currentRenderWidget().renderer().grayBand() == 1
 
     def test_syncToLayer_MultiBand(self):