Avoid possible crash in rendering loop

As soon as QgsMapLayer::setCacheImage is called while rendering is active, a crash occurs. Due to the fact, that processEvents is called from the main rendering loop, such situations cannot always be foreseen.
qgis · Apr 3, 2013 · 45cd49d · 45cd49d
1 parent 80f7b5a
commit 45cd49d
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Showing 6 changed files with 35 additions and 5 deletions.
diff --git a/src/app/qgsfieldsproperties.cpp b/src/app/qgsfieldsproperties.cpp
@@ -103,6 +103,7 @@ void QgsAttributesTree::dragMoveEvent( QDragMoveEvent *event )
 
 bool QgsAttributesTree::dropMimeData( QTreeWidgetItem * parent, int index, const QMimeData * data, Qt::DropAction action )
 {
+  Q_UNUSED( index )
   bool bDropSuccessful = false;
 
   if ( action == Qt::IgnoreAction )

diff --git a/src/core/qgsmaplayer.cpp b/src/core/qgsmaplayer.cpp
@@ -1249,6 +1249,7 @@ void QgsMapLayer::setCacheImage( QImage * thepImage )
 
   if ( mpCacheImage )
   {
+    onCacheImageDelete();
     delete mpCacheImage;
   }
   mpCacheImage = thepImage;

diff --git a/src/core/qgsmaplayer.h b/src/core/qgsmaplayer.h
@@ -331,6 +331,12 @@ class CORE_EXPORT QgsMapLayer : public QObject
      * @note This method was added in QGIS 1.4 **/
     void setCacheImage( QImage * thepImage );
 
+    /**
+     * @brief Is called when the cache image is being deleted. Overwrite and use to clean up.
+     * @note added in 2.0
+     */
+    virtual void onCacheImageDelete() {};
+
   public slots:
 
     /** Event handler for when a coordinate transform fails due to bad vertex error */

diff --git a/src/core/qgsmaprenderer.cpp b/src/core/qgsmaprenderer.cpp
@@ -544,7 +544,8 @@ void QgsMapRenderer::render( QPainter* painter, double* forceWidthScale )
           delete mRenderContext.painter();
           mRenderContext.setPainter( mypContextPainter );
           //draw from cached image that we created further up
-          mypContextPainter->drawImage( 0, 0, *( ml->cacheImage() ) );
+          if ( ml->cacheImage() )
+            mypContextPainter->drawImage( 0, 0, *( ml->cacheImage() ) );
         }
       }
       disconnect( ml, SIGNAL( drawingProgress( int, int ) ), this, SLOT( onDrawingProgress( int, int ) ) );

diff --git a/src/core/qgsvectorlayer.cpp b/src/core/qgsvectorlayer.cpp
@@ -107,6 +107,8 @@ QgsVectorLayer::QgsVectorLayer( QString vectorLayerPath,
     , mDiagramLayerSettings( 0 )
     , mValidExtent( false )
     , mSymbolFeatureCounted( false )
+    , mCurrentRendererContext( 0 )
+
 {
   mActions = new QgsAttributeAction( this );
 
@@ -718,6 +720,8 @@ void QgsVectorLayer::drawRendererV2( QgsFeatureIterator &fit, QgsRenderContext&
   if ( !hasGeometryType() )
     return;
 
+  mCurrentRendererContext = &rendererContext;
+
   QSettings settings;
   bool vertexMarkerOnlyForSelection = settings.value( "/qgis/digitizing/marker_only_for_selected", false ).toBool();
 
@@ -735,10 +739,6 @@ void QgsVectorLayer::drawRendererV2( QgsFeatureIterator &fit, QgsRenderContext&
       if ( !fet.geometry() )
         continue; // skip features without geometry
 
-      if ( rendererContext.renderingStopped() )
-      {
-        break;
-      }
 #ifndef Q_WS_MAC //MH: disable this on Mac for now to avoid problems with resizing
 #ifdef Q_WS_X11
       if ( !mEnableBackbuffer ) // do not handle events, as we're already inside a paint event
@@ -760,6 +760,11 @@ void QgsVectorLayer::drawRendererV2( QgsFeatureIterator &fit, QgsRenderContext&
 #endif // Q_WS_X11
 #endif // Q_WS_MAC
 
+      if ( rendererContext.renderingStopped() )
+      {
+        break;
+      }
+
       bool sel = mSelectedFeatureIds.contains( fet.id() );
       bool drawMarker = ( mEditBuffer && ( !vertexMarkerOnlyForSelection || sel ) );
 
@@ -798,6 +803,8 @@ void QgsVectorLayer::drawRendererV2( QgsFeatureIterator &fit, QgsRenderContext&
 
   stopRendererV2( rendererContext, NULL );
 
+  mCurrentRendererContext = NULL;
+
 #ifndef Q_WS_MAC
   QgsDebugMsg( QString( "Total features processed %1" ).arg( featureCount ) );
 #endif
@@ -4386,6 +4393,12 @@ QString QgsVectorLayer::metadata()
   return myMetadata;
 }
 
+void QgsVectorLayer::onCacheImageDelete()
+{
+  if ( mCurrentRendererContext )
+    mCurrentRendererContext->setRenderingStopped( true );
+}
+
 QgsVectorLayer::ValueRelationData &QgsVectorLayer::valueRelation( int idx )
 {
   const QgsFields &fields = pendingFields();

diff --git a/src/core/qgsvectorlayer.h b/src/core/qgsvectorlayer.h
@@ -879,6 +879,12 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
 
     inline QgsGeometryCache* cache() { return mCache; }
 
+    /**
+     * @brief Is called when the cache image is being deleted. Overwrite and use to clean up.
+     * @note added in 2.0
+     */
+    virtual void onCacheImageDelete();
+
   signals:
 
     /** This signal is emited when selection was changed */
@@ -1108,6 +1114,8 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
     // Feature counts for each renderer symbol
     QMap<QgsSymbolV2*, long> mSymbolFeatureCountMap;
 
+    QgsRenderContext* mCurrentRendererContext;
+
     friend class QgsVectorLayerFeatureIterator;
 };