better method to check if a canvas redraw is necessary after a drag in the legend

git-svn-id: http://svn.osgeo.org/qgis/trunk@4934 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: mhugent

src/legend/qgslegend.cpp

@@ -242,7 +242,6 @@ void QgsLegend::mouseMoveEvent(QMouseEvent * e)
 	    }
 	}     
     }
-    //QTreeWidget::mouseMoveEvent(e);
 }
 
 void QgsLegend::mouseReleaseEvent(QMouseEvent * e)
@@ -325,7 +324,13 @@ void QgsLegend::mouseReleaseEvent(QMouseEvent * e)
 		origLayer->setLegend((QgsLegend*)(dynamic_cast<QgsLegendItem*>(dest->parent())->nextSibling()));
 	      }
 	  }
-	emit zOrderChanged(this);
+	
+	std::deque<QString> layersAfterRelease = layerIDs(); //test if canvas redraw is really necessary
+	if(layersAfterRelease != mLayersPriorToMove)
+	  {
+	    emit zOrderChanged(this);
+	  }
+
       }
   }
   mMousePressedFlag = false;
@@ -989,6 +994,7 @@ void QgsLegend::storeInitialPosition(QTreeWidgetItem* li)
       mRestoreInformation = YOUNGER_SIBLING;
       mRestoreItem = ((QgsLegendItem*)(li))->findYoungerSibling();
     }
+  mLayersPriorToMove = layerIDs();
 }
 
 void QgsLegend::resetToInitialPosition(QTreeWidgetItem* li)

src/legend/qgslegend.h

@@ -222,6 +222,7 @@ this item may be moved back to the original position with resetToInitialPosition
   /**Returns the legend layer to which a map layer gelongs*/
   QgsLegendLayer* findLegendLayer(const QString& layerKey);
 
+
   private slots:
 
   /**Calls 'handleRightClickEvent' on the item*/
@@ -294,6 +295,10 @@ this item may be moved back to the original position with resetToInitialPosition
 
   bool mShowLegendLayerFiles;
 
+  /**Stores the layer ordering before a mouse Move. After the move, this is used to
+   decide if the mapcanvas really has to be refreshed*/
+  std::deque<QString> mLayersPriorToMove;
+
   /*!
    * A fuction sed to determin how far down in the list an item is (starting with one for the first Item.
    *If the item is not in the legend, -1 is returned