Fix for #707. When there were no features in provider, calculation started

with extent with null coordinates and extended it - that's reason of wrong extent


git-svn-id: http://svn.osgeo.org/qgis/trunk@7128 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: wonder

src/core/qgsvectorlayer.cpp

@@ -1131,23 +1131,25 @@ long QgsVectorLayer::updateFeatureCount() const
 
 void QgsVectorLayer::updateExtents()
 {
+  mLayerExtent.setMinimal();
+  
   if(mDataProvider)
   {
     if(mDeletedFeatureIds.isEmpty())
     {
       // get the extent of the layer from the provider
-      QgsRect r = mDataProvider->extent();
-      mLayerExtent.setXmin(r.xMin());
-      mLayerExtent.setYmin(r.yMin());
-      mLayerExtent.setXmax(r.xMax());
-      mLayerExtent.setYmax(r.yMax());
+      // but only when there are some features already
+      if (mDataProvider->featureCount() != 0)
+      {
+        QgsRect r = mDataProvider->extent();
+        mLayerExtent.combineExtentWith(&r);
+      }
     }
     else
     {
       QgsFeature fet;
       QgsRect bb;
 
-      mLayerExtent.setMinimal();
       mDataProvider->select();
       while (mDataProvider->getNextFeature(fet))
       {
@@ -1173,6 +1175,12 @@ void QgsVectorLayer::updateExtents()
     QgsRect bb = iter->geometry()->boundingBox();
     mLayerExtent.combineExtentWith(&bb);
   }
+  
+  if (mLayerExtent.xMin() > mLayerExtent.xMax() && mLayerExtent.yMin() > mLayerExtent.yMax())
+  {
+    // special case when there are no features in provider nor any added
+    mLayerExtent = QgsRect(); // use rectangle with zero coordinates
+  }
 
   // Send this (hopefully) up the chain to the map canvas
   emit recalculateExtents();
@@ -1201,12 +1209,6 @@ void QgsVectorLayer::setSubsetString(QString subset)
   mDataSource = mDataProvider->dataSourceUri();
   updateExtents();
 
-  //trigger a recalculate extents request to any attached canvases
-  QgsDebugMsg("Subset query changed, emitting recalculateExtents() signal");
-  
-  // emit the signal  to inform any listeners that the extent of this
-  // layer has changed
-  emit recalculateExtents();
 }