Fix new map canvas CRS is not accessible to QgsMapCanvasItem subclasses

in QgsMapCanvasItem::updatePosition() when this function is called as a result of map canvas CRS changes
qgis · Jan 18, 2021 · dc740eb · dc740eb
1 parent a9b89d3
commit dc740eb
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diff --git a/src/gui/qgsmapcanvas.cpp b/src/gui/qgsmapcanvas.cpp
@@ -417,11 +417,16 @@ void QgsMapCanvas::setDestinationCrs( const QgsCoordinateReferenceSystem &crs )
 
   if ( !rect.isEmpty() )
   {
+    // we will be manually calling updateCanvasItemPositions() later, AFTER setting the updating the mSettings destination CRS, and we don't
+    // want to do that twice!
+    mBlockItemPositionUpdates++;
     setExtent( rect );
+    mBlockItemPositionUpdates--;
   }
 
   mSettings.setDestinationCrs( crs );
   updateScale();
+  updateCanvasItemPositions();
 
   QgsDebugMsgLevel( QStringLiteral( "refreshing after destination CRS changed" ), 2 );
   refresh();
@@ -1996,6 +2001,9 @@ void QgsMapCanvas::paintEvent( QPaintEvent *e )
 
 void QgsMapCanvas::updateCanvasItemPositions()
 {
+  if ( mBlockItemPositionUpdates )
+    return;
+
   const QList<QGraphicsItem *> items = mScene->items();
   for ( QGraphicsItem *gi : items )
   {

diff --git a/src/gui/qgsmapcanvas.h b/src/gui/qgsmapcanvas.h
@@ -1304,6 +1304,8 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
 
     QList< QgsMapCanvasInteractionBlocker * > mInteractionBlockers;
 
+    int mBlockItemPositionUpdates = 0;
+
     /**
      * Returns the last cursor position on the canvas in geographical coordinates
      * \since QGIS 3.4