Raster renderer GUI: fix switching between renderers, and potential infinite signal notifications.

Fixes #3871 (comment), ie switching between
renderers in the raster layer properties dialog or in the style dock result in non optimal
parameters, so better switch to default parameters that would be the ones used when
adding a layer of the new renderer type to the canvas. This issue already existed in 2.18

Also fixes a potential infinite notification cycle when having both the style dock and
layer properties dialog opened, and applying changes in the layer properties dialog.
(related to #3871).

Author: rouault

src/app/qgsrasterlayerproperties.cpp

@@ -549,6 +549,19 @@ void QgsRasterLayerProperties::setRendererWidget( const QString& rendererName )
       QgsDebugMsg( "renderer has widgetCreateFunction" );
       // Current canvas extent (used to calc min/max) in layer CRS
       QgsRectangle myExtent = mMapCanvas->mapSettings().outputExtentToLayerExtent( mRasterLayer, mMapCanvas->extent() );
+      if ( oldWidget )
+      {
+        if ( rendererName == "singlebandgray" )
+        {
+          whileBlocking( mRasterLayer )->setRenderer( QgsRasterRendererRegistry::instance()->defaultRendererForDrawingStyle( QgsRaster::SingleBandGray, mRasterLayer->dataProvider() ) );
+          whileBlocking( mRasterLayer )->setDefaultContrastEnhancement();
+        }
+        else if ( rendererName == "multibandcolor" )
+        {
+          whileBlocking( mRasterLayer )->setRenderer( QgsRasterRendererRegistry::instance()->defaultRendererForDrawingStyle( QgsRaster::MultiBandColor, mRasterLayer->dataProvider() ) );
+          whileBlocking( mRasterLayer )->setDefaultContrastEnhancement();
+        }
+      }
       mRendererWidget = rendererEntry.widgetCreateFunction( mRasterLayer, myExtent );
       mRendererWidget->setMapCanvas( mMapCanvas );
       mRendererStackedWidget->addWidget( mRendererWidget );

src/gui/raster/qgsmultibandcolorrendererwidget.cpp

@@ -81,13 +81,6 @@ QgsMultiBandColorRendererWidget::QgsMultiBandColorRendererWidget( QgsRasterLayer
     onBandChanged( 0 ); // reset mMinMaxWidget bands
 
     connect( mContrastEnhancementAlgorithmComboBox, SIGNAL( currentIndexChanged( int ) ), this, SIGNAL( widgetChanged() ) );
-    connect( mRedMinLineEdit, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
-    connect( mRedMaxLineEdit, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
-    connect( mGreenMaxLineEdit, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
-    connect( mGreenMinLineEdit, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
-    connect( mBlueMaxLineEdit, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
-    connect( mBlueMinLineEdit, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
-
   }
 }
 
@@ -267,6 +260,7 @@ void QgsMultiBandColorRendererWidget::minMaxModified()
         mContrastEnhancementAlgorithmComboBox->findData(( int ) QgsContrastEnhancement::StretchToMinimumMaximum ) );
     }
     mMinMaxWidget->userHasSetManualMinMaxValues();
+    emit widgetChanged();
   }
 }
 

src/gui/raster/qgsrendererrasterpropertieswidget.cpp

@@ -333,6 +333,19 @@ void QgsRendererRasterPropertiesWidget::setRendererWidget( const QString &render
       QgsDebugMsg( "renderer has widgetCreateFunction" );
       // Current canvas extent (used to calc min/max) in layer CRS
       QgsRectangle myExtent = mMapCanvas->mapSettings().outputExtentToLayerExtent( mRasterLayer, mMapCanvas->extent() );
+      if ( oldWidget )
+      {
+        if ( rendererName == "singlebandgray" )
+        {
+          whileBlocking( mRasterLayer )->setRenderer( QgsRasterRendererRegistry::instance()->defaultRendererForDrawingStyle( QgsRaster::SingleBandGray, mRasterLayer->dataProvider() ) );
+          whileBlocking( mRasterLayer )->setDefaultContrastEnhancement();
+        }
+        else if ( rendererName == "multibandcolor" )
+        {
+          whileBlocking( mRasterLayer )->setRenderer( QgsRasterRendererRegistry::instance()->defaultRendererForDrawingStyle( QgsRaster::MultiBandColor, mRasterLayer->dataProvider() ) );
+          whileBlocking( mRasterLayer )->setDefaultContrastEnhancement();
+        }
+      }
       mRendererWidget = rendererEntry.widgetCreateFunction( mRasterLayer, myExtent );
       mRendererWidget->setMapCanvas( mMapCanvas );
       connect( mRendererWidget, SIGNAL( widgetChanged() ), this, SIGNAL( widgetChanged() ) );

src/gui/raster/qgssinglebandgrayrendererwidget.cpp

@@ -74,8 +74,6 @@ QgsSingleBandGrayRendererWidget::QgsSingleBandGrayRendererWidget( QgsRasterLayer
 
     connect( mGradientComboBox, SIGNAL( currentIndexChanged( int ) ), this, SIGNAL( widgetChanged() ) );
     connect( mContrastEnhancementComboBox, SIGNAL( currentIndexChanged( int ) ), this, SIGNAL( widgetChanged() ) );
-    connect( mMaxLineEdit, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
-    connect( mMinLineEdit, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
   }
 }
 
@@ -142,6 +140,7 @@ void QgsSingleBandGrayRendererWidget::minMaxModified()
         mContrastEnhancementComboBox->findData(( int ) QgsContrastEnhancement::StretchToMinimumMaximum ) );
     }
     mMinMaxWidget->userHasSetManualMinMaxValues();
+    emit widgetChanged();
   }
 }