fix advanced digitizing panel display issue after panning

panning would cause the rubberbands of the adv. digit. panel to be invisible.
update the canvas item is now done after each extent changes

src/gui/qgsmapcanvas.cpp

@@ -183,6 +183,8 @@ QgsMapCanvas::QgsMapCanvas( QWidget *parent )
 
   connect( &mAutoRefreshTimer, &QTimer::timeout, this, &QgsMapCanvas::autoRefreshTriggered );
 
+  connect( this, &QgsMapCanvas::extentsChanged, this, &QgsMapCanvas::updateCanvasItemPositions );
+
   setInteractive( false );
 
   refresh();
@@ -790,9 +792,6 @@ void QgsMapCanvas::setExtent( const QgsRectangle &r, bool magnified )
   // update controls' enabled state
   emit zoomLastStatusChanged( mLastExtentIndex > 0 );
   emit zoomNextStatusChanged( mLastExtentIndex < mLastExtent.size() - 1 );
-  // notify canvas items of change
-  updateCanvasItemPositions();
-
 } // setExtent
 
 void QgsMapCanvas::setCenter( const QgsPointXY &center )
@@ -831,10 +830,6 @@ void QgsMapCanvas::setRotation( double degrees )
   mSettings.setRotation( degrees );
   emit rotationChanged( degrees );
   emit extentsChanged(); // visible extent changes with rotation
-
-  // notify canvas items of change (needed?)
-  updateCanvasItemPositions();
-
 } // setRotation
 
 
@@ -890,8 +885,6 @@ void QgsMapCanvas::zoomToNextExtent()
     // update controls' enabled state
     emit zoomLastStatusChanged( mLastExtentIndex > 0 );
     emit zoomNextStatusChanged( mLastExtentIndex < mLastExtent.size() - 1 );
-    // notify canvas items of change
-    updateCanvasItemPositions();
   }
 }// zoomToNextExtent