Convenience auto setup features when adding new layers

On first layer: zoom to full extent, setup destination CRS and map units
On first layer with different CRS: enable OTF reprojection

This functionality is not triggered when opening an existing project.

src/app/qgisapp.cpp

@@ -2233,8 +2233,8 @@ void QgisApp::initLayerTreeView()
   mLayerTreeDock->setWidget( mLayerTreeView );
   addDockWidget( Qt::LeftDockWidgetArea, mLayerTreeDock );
 
-  QgsLayerTreeMapCanvasBridge* bridge = new QgsLayerTreeMapCanvasBridge( QgsProject::instance()->layerTreeRoot(), mMapCanvas );
-  bridge->setParent(this);
+  mLayerTreeCanvasBridge = new QgsLayerTreeMapCanvasBridge( QgsProject::instance()->layerTreeRoot(), mMapCanvas );
+  mLayerTreeCanvasBridge->setParent(this);
 }
 
 
@@ -9458,6 +9458,13 @@ void QgisApp::writeProject( QDomDocument &doc )
 void QgisApp::readProject( const QDomDocument &doc )
 {
   projectChanged( doc );
+
+  // force update of canvas, without automatic changes to extent and OTF projections
+  mLayerTreeCanvasBridge->setAutoEnableCrsTransform( false );
+  mLayerTreeCanvasBridge->setAutoSetupOnFirstLayer( false );
+  mLayerTreeCanvasBridge->setCanvasLayers();
+  mLayerTreeCanvasBridge->setAutoEnableCrsTransform( true );
+  mLayerTreeCanvasBridge->setAutoSetupOnFirstLayer( true );
 }
 
 void QgisApp::showLayerProperties( QgsMapLayer *ml )

src/app/qgisapp.h

@@ -46,6 +46,7 @@ class QgsComposerManager;
 class QgsContrastEnhancement;
 class QgsGeometry;
 class QgsFeature;
+class QgsLayerTreeMapCanvasBridge;
 class QgsLayerTreeView;
 class QgsLegend;
 class QgsLayerOrder;
@@ -1472,6 +1473,8 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
     QgsMapCanvas *mMapCanvas;
     //! Table of contents (legend) for the map
     QgsLayerTreeView* mLayerTreeView;
+    //! Helper class that connects layer tree with map canvas
+    QgsLayerTreeMapCanvasBridge* mLayerTreeCanvasBridge;
     //! Table of contents (legend) for the map
     QgsLegend *mMapLegend;
     //! Table of contents (legend) to order layers of the map

src/gui/layertree/qgslayertreemapcanvasbridge.cpp

@@ -9,6 +9,9 @@ QgsLayerTreeMapCanvasBridge::QgsLayerTreeMapCanvasBridge(QgsLayerTreeGroup *root
   , mCanvas(canvas)
   , mPendingCanvasUpdate(false)
   , mHasCustomLayerOrder(false)
+  , mAutoSetupOnFirstLayer(true)
+  , mAutoEnableCrsTransform(true)
+  , mLastLayerCount(root->findLayers().count())
 {
   connect(root, SIGNAL(addedChildren(QgsLayerTreeNode*,int,int)), this, SLOT(nodeAddedChildren(QgsLayerTreeNode*,int,int)));
   connect(root, SIGNAL(customPropertyChanged(QgsLayerTreeNode*,QString)), this, SLOT(nodeCustomPropertyChanged(QgsLayerTreeNode*,QString)));
@@ -87,6 +90,59 @@ void QgsLayerTreeMapCanvasBridge::setCanvasLayers()
 
   mCanvas->setLayerSet(layers);
 
+  QList<QgsLayerTreeLayer*> layerNodes = mRoot->findLayers();
+
+  int currentLayerCount = layerNodes.count();
+  if (mAutoSetupOnFirstLayer && mLastLayerCount == 0 && currentLayerCount != 0)
+  {
+    // if we are moving from zero to non-zero layers, let's zoom to those data
+    mCanvas->zoomToFullExtent();
+
+    // also setup destination CRS and map units if the OTF projections are not yet enabled
+    if (!mCanvas->mapSettings().hasCrsTransformEnabled())
+    {
+      foreach (QgsLayerTreeLayer* layerNode, layerNodes)
+      {
+        if (layerNode->layer())
+        {
+          mCanvas->setDestinationCrs( layerNode->layer()->crs() );
+          mCanvas->setMapUnits( layerNode->layer()->crs().mapUnits() );
+        }
+      }
+    }
+  }
+
+  if (!mFirstCRS.isValid())
+  {
+    // find out what is the first used CRS in case we may need to turn on OTF projections later
+    foreach (QgsLayerTreeLayer* layerNode, layerNodes)
+    {
+      if (layerNode->layer() && layerNode->layer()->crs().isValid())
+      {
+        mFirstCRS = layerNode->layer()->crs();
+        break;
+      }
+    }
+  }
+
+  if (mAutoEnableCrsTransform && mFirstCRS.isValid() && !mCanvas->mapSettings().hasCrsTransformEnabled())
+  {
+    // check whether all layers still have the same CRS
+    foreach (QgsLayerTreeLayer* layerNode, layerNodes)
+    {
+      if (layerNode->layer() && layerNode->layer()->crs().isValid() && layerNode->layer()->crs() != mFirstCRS)
+      {
+        mCanvas->setDestinationCrs( mFirstCRS );
+        mCanvas->setCrsTransformEnabled( true );
+        break;
+      }
+    }
+  }
+
+  mLastLayerCount = currentLayerCount;
+  if (currentLayerCount == 0)
+    mFirstCRS = QgsCoordinateReferenceSystem();
+
   mPendingCanvasUpdate = false;
 }
 

src/gui/layertree/qgslayertreemapcanvasbridge.h

@@ -4,6 +4,8 @@
 #include <QObject>
 #include <QStringList>
 
+#include "qgscoordinatereferencesystem.h"
+
 class QgsMapCanvas;
 class QgsMapCanvasLayer;
 class QgsLayerTreeGroup;
@@ -20,10 +22,23 @@ class GUI_EXPORT QgsLayerTreeMapCanvasBridge : public QObject
 
   QStringList defaultLayerOrder() const;
 
+  //! if enabled, will automatically set full canvas extent and destination CRS + map units
+  //! when first layer(s) are added
+  void setAutoSetupOnFirstLayer(bool enabled) { mAutoSetupOnFirstLayer = enabled; }
+  bool autoSetupOnFirstLayer() const { return mAutoSetupOnFirstLayer; }
+
+  //! if enabled, will automatically turn on on-the-fly reprojection of layers if a layer
+  //! with different source CRS is added
+  void setAutoEnableCrsTransform(bool enabled) { mAutoEnableCrsTransform = enabled; }
+  bool autoEnableCrsTransform() const { return mAutoEnableCrsTransform; }
+
 public slots:
   void setHasCustomLayerOrder(bool override);
   void setCustomLayerOrder(const QStringList& order);
 
+  //! force update of canvas layers from the layer tree. Normally this should not be needed to be called.
+  void setCanvasLayers();
+
 signals:
   void hasCustomLayerOrderChanged(bool);
   void customLayerOrderChanged(const QStringList& order);
@@ -42,8 +57,6 @@ protected slots:
   void nodeVisibilityChanged();
   void nodeCustomPropertyChanged(QgsLayerTreeNode* node, QString key);
 
-  void setCanvasLayers();
-
 protected:
   QgsLayerTreeGroup* mRoot;
   QgsMapCanvas* mCanvas;
@@ -52,6 +65,13 @@ protected slots:
 
   bool mHasCustomLayerOrder;
   QStringList mCustomLayerOrder;
+
+  bool mAutoSetupOnFirstLayer;
+  bool mAutoEnableCrsTransform;
+
+  bool mHasFirstLayer;
+  bool mLastLayerCount;
+  QgsCoordinateReferenceSystem mFirstCRS;
 };
 
 #endif // QGSLAYERTREEMAPCANVASBRIDGE_H