Make sure main canvas is always synced to project CRS (part 1)

Fix #16337

src/app/qgisapp.cpp

@@ -2840,9 +2840,14 @@ void QgisApp::setupConnections()
   connect( mMapCanvas, &QgsMapCanvas::keyPressed,
            this, &QgisApp::mapCanvas_keyPressed );
 
-  // connect renderer
-  connect( mMapCanvas, &QgsMapCanvas::destinationCrsChanged,
-           this, &QgisApp::destinationCrsChanged );
+  // project crs connections
+  connect( QgsProject::instance(), &QgsProject::crsChanged,
+           this, &QgisApp::updateCrsStatusBar );
+  connect( QgsProject::instance(), &QgsProject::crsChanged,
+           this, [ = ]
+  {
+    mMapCanvas->setDestinationCrs( QgsProject::instance()->crs() );
+  } );
 
   // connect legend signals
   connect( mLayerTreeView, SIGNAL( currentLayerChanged( QgsMapLayer * ) ),
@@ -4626,13 +4631,10 @@ void QgisApp::fileNew( bool promptToSaveFlag, bool forceBlank )
   // set project CRS
   QString defCrs = settings.value( QStringLiteral( "Projections/projectDefaultCrs" ), GEO_EPSG_CRS_AUTHID ).toString();
   QgsCoordinateReferenceSystem srs = QgsCoordinateReferenceSystem::fromOgcWmsCrs( defCrs );
-  mMapCanvas->setDestinationCrs( srs );
   // write the projections _proj string_ to project settings
   prj->setCrs( srs );
   prj->setDirty( false );
 
-  updateCrsStatusBar();
-
   /** New Empty Project Created
       (before attempting to load custom project templates/filepaths) */
 
@@ -8791,7 +8793,6 @@ void QgisApp::setProjectCrsFromLayer()
 
   QgsCoordinateReferenceSystem crs = mLayerTreeView->currentLayer()->crs();
   mMapCanvas->freeze();
-  mMapCanvas->setDestinationCrs( crs );
   QgsProject::instance()->setCrs( crs );
   mMapCanvas->freeze( false );
   mMapCanvas->refresh();
@@ -10316,11 +10317,6 @@ void QgisApp::updateCrsStatusBar()
   }
 }
 
-void QgisApp::destinationCrsChanged()
-{
-  updateCrsStatusBar();
-}
-
 // slot to update the progress bar in the status bar
 void QgisApp::showProgress( int progress, int totalSteps )
 {

src/app/qgisapp.h

@@ -1204,7 +1204,6 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
     void displayMessage( const QString &title, const QString &message, QgsMessageBar::MessageLevel level );
     void removeMapToolMessage();
     void updateMouseCoordinatePrecision();
-    void destinationCrsChanged();
     //    void debugHook();
     //! Add a Layer Definition file
     void addLayerDefinition();
@@ -1396,6 +1395,8 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
 
     void annotationCreated( QgsAnnotation *annotation );
 
+    void updateCrsStatusBar();
+
   signals:
 
     /** Emitted when a key is pressed and we want non widget sublasses to be able
@@ -1531,7 +1532,6 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
     void createOverview();
     void createCanvasTools();
     void createMapTips();
-    void updateCrsStatusBar();
     void createDecorations();
 
     //! Do histogram stretch for singleband gray / multiband color rasters

src/app/qgsprojectproperties.cpp

@@ -734,7 +734,6 @@ void QgsProjectProperties::apply()
   {
     QgsCoordinateReferenceSystem srs = projectionSelector->crs();
     QgsProject::instance()->setCrs( srs );
-    mMapCanvas->setDestinationCrs( srs );
     if ( srs.isValid() )
     {
       QgsDebugMsg( QString( "Selected CRS " ) + srs.description() );

src/gui/layertree/qgslayertreemapcanvasbridge.cpp

@@ -170,7 +170,6 @@ void QgsLayerTreeMapCanvasBridge::setCanvasLayers()
 
   if ( mFirstCRS.isValid() && firstLayers )
   {
-    mCanvas->setDestinationCrs( mFirstCRS );
     QgsProject::instance()->setCrs( mFirstCRS );
   }