Browser: correct drag&drop for canvas and browser itself

wonder-sk · wonder-sk · commit 173c72db48f8 · 2011-08-12T23:38:47.000+02:00
diff --git a/src/app/qgsbrowserdockwidget.cpp b/src/app/qgsbrowserdockwidget.cpp
@@ -11,16 +11,45 @@
 #include "qgsrasterlayer.h"
 #include "qgsvectorlayer.h"
 
+#include <QDragEnterEvent>
+/**
+Utility class for correct drag&drop handling.
+
+We want to allow user to drag layers to qgis window. At the same time we do not
+accept drops of the items on our view - but if we ignore the drag enter action
+then qgis application consumes the drag events and it is possible to drop the
+items on the tree view although the drop is actually managed by qgis app.
+ */
+class QgsBrowserTreeView : public QTreeView
+{
+public:
+  QgsBrowserTreeView( QWidget* parent ) : QTreeView(parent)
+  {
+    setDragDropMode( QTreeView::DragDrop ); // sets also acceptDrops + dragEnabled
+    setSelectionMode( QAbstractItemView::ExtendedSelection );
+    setContextMenuPolicy( Qt::CustomContextMenu );
+  }
+
+  void dragEnterEvent(QDragEnterEvent* e)
+  {
+    // accept drag enter so that our widget will not get ignored
+    // and drag events will not get passed to QgisApp
+    e->accept();
+  }
+  void dragMoveEvent(QDragMoveEvent* e)
+  {
+    // ignore all possibilities where an item could be dropped
+    // because we want that user drops the item on canvas / legend / app
+    e->ignore();
+  }
+};
+
 QgsBrowserDockWidget::QgsBrowserDockWidget( QWidget * parent ) :
     QDockWidget( parent ), mModel( NULL )
 {
   setWindowTitle( tr( "Browser" ) );
 
-  mBrowserView = new QTreeView( this );
-  mBrowserView->setDragEnabled( true );
-  mBrowserView->setDragDropMode( QTreeView::DragOnly );
-  mBrowserView->setSelectionMode( QAbstractItemView::ExtendedSelection );
-  mBrowserView->setContextMenuPolicy( Qt::CustomContextMenu );
+  mBrowserView = new QgsBrowserTreeView( this );
   setWidget( mBrowserView );
 
   connect( mBrowserView, SIGNAL( customContextMenuRequested( const QPoint & ) ), this, SLOT( showContextMenu( const QPoint & ) ) );
diff --git a/src/gui/qgsmapcanvas.cpp b/src/gui/qgsmapcanvas.cpp
@@ -1499,3 +1499,11 @@ void QgsMapCanvas::selectionChangedSlot()
   emit selectionChanged( layer );
   refresh();
 }
+
+void QgsMapCanvas::dragEnterEvent( QDragEnterEvent * e )
+{
+  // By default graphics view delegates the drag events to graphics items.
+  // But we do not want that and by ignoring the drag enter we let the
+  // parent (e.g. QgisApp) to handle drops of map layers etc.
+  e->ignore();
+}
diff --git a/src/gui/qgsmapcanvas.h b/src/gui/qgsmapcanvas.h
@@ -376,6 +376,9 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
     //! Overridden paint event
     void paintEvent( QPaintEvent * e );
 
+    //! Overridden drag enter event
+    void dragEnterEvent( QDragEnterEvent * e );
+
     //! called when panning is in action, reset indicates end of panning
     void moveCanvasContents( bool reset = false );
 
