Allow vector rendering cancelation to also cancel feature iteration f…

…or that request

Connect the cancel rendering signal to the iteration cancelation.
This allows providers (e.g. WFS, AFS) to abort slow network requests
when they have been triggered by a render request and that request
is no longer required.

Allows much faster quit, render cancelation when using WFS/AFS layers.

(cherry picked from commit 6fa3bf8)

src/core/qgsvectorlayerrenderer.cpp

@@ -42,7 +42,7 @@
 QgsVectorLayerRenderer::QgsVectorLayerRenderer( QgsVectorLayer *layer, QgsRenderContext &context )
   : QgsMapLayerRenderer( layer->id() )
   , mContext( context )
-  , mInterruptionChecker( context )
+  , mInterruptionChecker( qgis::make_unique< QgsVectorLayerRendererInterruptionChecker >( context ) )
   , mLayer( layer )
   , mFields( layer->fields() )
   , mLabeling( false )
@@ -106,6 +106,10 @@ QgsVectorLayerRenderer::~QgsVectorLayerRenderer()
   delete mSource;
 }
 
+QgsFeedback *QgsVectorLayerRenderer::feedback() const
+{
+  return mInterruptionChecker.get();
+}
 
 bool QgsVectorLayerRenderer::render()
 {
@@ -239,7 +243,7 @@ bool QgsVectorLayerRenderer::render()
   // slow fetchFeature() implementations, such as in the WFS provider, can
   // check it, instead of relying on just the mContext.renderingStopped() check
   // in drawRenderer()
-  fit.setInterruptionChecker( &mInterruptionChecker );
+  fit.setInterruptionChecker( mInterruptionChecker.get() );
 
   if ( ( mRenderer->capabilities() & QgsFeatureRenderer::SymbolLevels ) && mRenderer->usingSymbolLevels() )
     drawRendererLevels( fit );

src/core/qgsvectorlayerrenderer.h

@@ -76,6 +76,7 @@ class QgsVectorLayerRenderer : public QgsMapLayerRenderer
   public:
     QgsVectorLayerRenderer( QgsVectorLayer *layer, QgsRenderContext &context );
     ~QgsVectorLayerRenderer() override;
+    QgsFeedback *feedback() const override;
 
     bool render() override;
 
@@ -107,7 +108,7 @@ class QgsVectorLayerRenderer : public QgsMapLayerRenderer
 
     QgsRenderContext &mContext;
 
-    QgsVectorLayerRendererInterruptionChecker mInterruptionChecker;
+    std::unique_ptr< QgsVectorLayerRendererInterruptionChecker > mInterruptionChecker;
 
     //! The rendered layer
     QgsVectorLayer *mLayer = nullptr;