Allow canvas extents to be synchronized

Author: nyalldawson

src/app/qgisapp.cpp

@@ -3126,6 +3126,7 @@ QgsMapCanvas *QgisApp::createNewMapCanvas( const QString &name, bool isFloating,
 
   QgsMapCanvasDockWidget *mapCanvasWidget = new QgsMapCanvasDockWidget( name, this );
   mapCanvasWidget->setAllowedAreas( Qt::AllDockWidgetAreas );
+  mapCanvasWidget->setMainCanvas( mMapCanvas );
 
   mapCanvasWidget->setFloating( isFloating );
   if ( dockGeometry.isEmpty() )

src/app/qgsmapcanvasdockwidget.cpp

@@ -37,6 +37,7 @@ QgsMapCanvasDockWidget::QgsMapCanvasDockWidget( const QString &name, QWidget *pa
   mMainWidget->layout()->addWidget( mMapCanvas );
 
   connect( mActionSetCrs, &QAction::triggered, this, &QgsMapCanvasDockWidget::setMapCrs );
+  connect( mActionSyncView, &QAction::toggled, this, &QgsMapCanvasDockWidget::syncView );
 }
 
 QgsMapCanvas *QgsMapCanvasDockWidget::mapCanvas()
@@ -75,3 +76,33 @@ void QgsMapCanvasDockWidget::setMapCrs()
     mMapCanvas->setDestinationCrs( dlg.crs() );
   }
 }
+
+void QgsMapCanvasDockWidget::syncView( bool enabled )
+{
+  if ( enabled )
+  {
+    connect( mMainCanvas, &QgsMapCanvas::extentsChanged, this, &QgsMapCanvasDockWidget::mapExtentChanged, Qt::UniqueConnection );
+    connect( mMapCanvas, &QgsMapCanvas::extentsChanged, this, &QgsMapCanvasDockWidget::mapExtentChanged, Qt::UniqueConnection );
+  }
+  else
+  {
+    disconnect( mMainCanvas, &QgsMapCanvas::extentsChanged, this, &QgsMapCanvasDockWidget::mapExtentChanged );
+    disconnect( mMapCanvas, &QgsMapCanvas::extentsChanged, this, &QgsMapCanvasDockWidget::mapExtentChanged );
+  }
+}
+
+void QgsMapCanvasDockWidget::mapExtentChanged()
+{
+  QgsMapCanvas *sourceCanvas = qobject_cast< QgsMapCanvas * >( sender() );
+  if ( !sourceCanvas )
+    return;
+
+  // avoid infinite recursion
+  syncView( false );
+
+  QgsMapCanvas *destCanvas = sourceCanvas == mMapCanvas ? mMainCanvas : mMapCanvas;
+  destCanvas->setExtent( sourceCanvas->extent() );
+  destCanvas->refresh();
+
+  syncView( true );
+}

src/app/qgsmapcanvasdockwidget.h

@@ -28,6 +28,11 @@ class APP_EXPORT QgsMapCanvasDockWidget : public QgsDockWidget, private Ui::QgsM
   public:
     explicit QgsMapCanvasDockWidget( const QString &name, QWidget *parent = nullptr );
 
+    /**
+     * Sets the main app map canvas.
+     */
+    void setMainCanvas( QgsMapCanvas *canvas ) { mMainCanvas = canvas; }
+
     /**
      * Returns the map canvas contained in the dock widget.
      */
@@ -45,10 +50,13 @@ class APP_EXPORT QgsMapCanvasDockWidget : public QgsDockWidget, private Ui::QgsM
   private slots:
 
     void setMapCrs();
+    void syncView( bool enabled );
+    void mapExtentChanged();
 
   private:
 
     QgsMapCanvas *mMapCanvas = nullptr;
+    QgsMapCanvas *mMainCanvas = nullptr;
     bool mShowCloseWarning = true;
 
 

src/ui/qgsmapcanvasdockwidgetbase.ui

@@ -42,6 +42,7 @@
        <bool>false</bool>
       </property>
       <addaction name="mActionSetCrs"/>
+      <addaction name="mActionSyncView"/>
      </widget>
     </item>
     <item>
@@ -79,6 +80,21 @@
     <string>Set Map CRS</string>
    </property>
   </action>
+  <action name="mActionSyncView">
+   <property name="checkable">
+    <bool>true</bool>
+   </property>
+   <property name="icon">
+    <iconset resource="../../images/images.qrc">
+     <normaloff>:/images/themes/default/sync_views.svg</normaloff>:/images/themes/default/sync_views.svg</iconset>
+   </property>
+   <property name="text">
+    <string>Synchronize view</string>
+   </property>
+   <property name="toolTip">
+    <string>Synchronize View with Main Map</string>
+   </property>
+  </action>
  </widget>
  <customwidgets>
   <customwidget>