[FEATURE] Drag'n'drop layers from layer tree view to browser dock

Makes it easy to e.g. store your temporary layers in PostGIS

python/core/qgsmimedatautils.sip

@@ -40,4 +40,10 @@ class QgsMimeDataUtils
 
     static UriList decodeUriList( const QMimeData* data );
 
+    /**
+     * Returns encoded URI list from a list of layer tree nodes.
+     * @note added in QGIS 3.0
+     */
+    static QByteArray layerTreeNodesToUriList( const QList<QgsLayerTreeNode*>& nodes );
+
 };

src/app/qgisapp.cpp

@@ -1273,7 +1273,9 @@ void QgisApp::dragEnterEvent( QDragEnterEvent *event )
 {
   if ( event->mimeData()->hasUrls() || event->mimeData()->hasFormat( "application/x-vnd.qgis.qgis.uri" ) )
   {
-    event->acceptProposedAction();
+    // the mime data are coming from layer tree, so ignore that, do not import those layers again
+    if ( !event->mimeData()->hasFormat( "application/qgis.layertreemodeldata" ) )
+      event->acceptProposedAction();
   }
 }
 

src/app/qgsbrowserdockwidget.cpp

@@ -767,6 +767,12 @@ QgsDockBrowserTreeView::QgsDockBrowserTreeView( QWidget* parent ) : QgsBrowserTr
 
 void QgsDockBrowserTreeView::dragEnterEvent( QDragEnterEvent* e )
 {
+  // if this mime data come from layer tree, the proposed action will be MoveAction
+  // but for browser we really need CopyAction
+  if ( e->mimeData()->hasFormat( "application/qgis.layertreemodeldata" ) &&
+       e->mimeData()->hasFormat( "application/x-vnd.qgis.qgis.uri" ) )
+    e->setDropAction( Qt::CopyAction );
+
   // accept drag enter so that our widget will not get ignored
   // and drag events will not get passed to QgisApp
   e->accept();
@@ -782,6 +788,12 @@ void QgsDockBrowserTreeView::dragMoveEvent( QDragMoveEvent* e )
         return;
       }*/
 
+  // if this mime data come from layer tree, the proposed action will be MoveAction
+  // but for browser we really need CopyAction
+  if ( e->mimeData()->hasFormat( "application/qgis.layertreemodeldata" ) &&
+       e->mimeData()->hasFormat( "application/x-vnd.qgis.qgis.uri" ) )
+    e->setDropAction( Qt::CopyAction );
+
   QTreeView::dragMoveEvent( e );
 
   if ( !e->mimeData()->hasFormat( "application/x-vnd.qgis.qgis.uri" ) )
@@ -791,6 +803,17 @@ void QgsDockBrowserTreeView::dragMoveEvent( QDragMoveEvent* e )
   }
 }
 
+void QgsDockBrowserTreeView::dropEvent( QDropEvent *e )
+{
+  // if this mime data come from layer tree, the proposed action will be MoveAction
+  // but for browser we really need CopyAction
+  if ( e->mimeData()->hasFormat( "application/qgis.layertreemodeldata" ) &&
+       e->mimeData()->hasFormat( "application/x-vnd.qgis.qgis.uri" ) )
+    e->setDropAction( Qt::CopyAction );
+
+  QTreeView::dropEvent( e );
+}
+
 
 //
 // QgsBrowserTreeFilterProxyModel

src/app/qgsbrowserdockwidget.h

@@ -173,6 +173,7 @@ class QgsDockBrowserTreeView : public QgsBrowserTreeView
 
     void dragEnterEvent( QDragEnterEvent* e ) override;
     void dragMoveEvent( QDragMoveEvent* e ) override;
+    void dropEvent( QDropEvent* e ) override;
 };
 
 /**

src/core/layertree/qgslayertreemodel.cpp

@@ -1011,6 +1011,9 @@ QMimeData* QgsLayerTreeModel::mimeData( const QModelIndexList& indexes ) const
   QString txt = doc.toString();
 
   mimeData->setData( "application/qgis.layertreemodeldata", txt.toUtf8() );
+
+  mimeData->setData( "application/x-vnd.qgis.qgis.uri", QgsMimeDataUtils::layerTreeNodesToUriList( nodesFinal ) );
+
   return mimeData;
 }
 

src/core/qgsmimedatautils.cpp

@@ -17,7 +17,13 @@
 #include "qgsmimedatautils.h"
 
 #include "qgsdataitem.h"
+#include "qgslayertree.h"
 #include "qgslogger.h"
+#include "qgspluginlayer.h"
+#include "qgsrasterdataprovider.h"
+#include "qgsrasterlayer.h"
+#include "qgsvectordataprovider.h"
+#include "qgsvectorlayer.h"
 
 static const char* QGIS_URILIST_MIMETYPE = "application/x-vnd.qgis.qgis.uri";
 
@@ -70,15 +76,8 @@ bool QgsMimeDataUtils::isUriList( const QMimeData* data )
 QMimeData* QgsMimeDataUtils::encodeUriList( const QgsMimeDataUtils::UriList& layers )
 {
   QMimeData *mimeData = new QMimeData();
-  QByteArray encodedData;
 
-  QDataStream stream( &encodedData, QIODevice::WriteOnly );
-  Q_FOREACH ( const Uri& u, layers )
-  {
-    stream << u.data();
-  }
-
-  mimeData->setData( QGIS_URILIST_MIMETYPE, encodedData );
+  mimeData->setData( QGIS_URILIST_MIMETYPE, uriListToByteArray( layers ) );
   return mimeData;
 }
 
@@ -98,6 +97,52 @@ QgsMimeDataUtils::UriList QgsMimeDataUtils::decodeUriList( const QMimeData* data
   return list;
 }
 
+
+static void _addLayerTreeNodeToUriList( QgsLayerTreeNode* node, QgsMimeDataUtils::UriList& uris )
+{
+  if ( QgsLayerTree::isGroup( node ) )
+  {
+    Q_FOREACH ( QgsLayerTreeNode* child, QgsLayerTree::toGroup( node )->children() )
+      _addLayerTreeNodeToUriList( child, uris );
+  }
+  else if ( QgsLayerTree::isLayer( node ) )
+  {
+    QgsLayerTreeLayer* nodeLayer = QgsLayerTree::toLayer( node );
+    if ( !nodeLayer->layer() )
+      return;
+
+    QgsMimeDataUtils::Uri uri;
+    if ( QgsVectorLayer* vlayer = qobject_cast<QgsVectorLayer*>( nodeLayer->layer() ) )
+    {
+      uri.layerType = "vector";
+      uri.name = vlayer->name();
+      uri.providerKey = vlayer->dataProvider()->name();
+      uri.uri = vlayer->dataProvider()->dataSourceUri();
+    }
+    else if ( QgsRasterLayer* rlayer = qobject_cast<QgsRasterLayer*>( nodeLayer->layer() ) )
+    {
+      uri.layerType = "raster";
+      uri.name = rlayer->name();
+      uri.providerKey = rlayer->dataProvider()->name();
+      uri.uri = rlayer->dataProvider()->dataSourceUri();
+    }
+    else
+    {
+      // plugin layers do not have a standard way of storing their URI...
+      return;
+    }
+    uris << uri;
+  }
+}
+
+QByteArray QgsMimeDataUtils::layerTreeNodesToUriList( const QList<QgsLayerTreeNode *>& nodes )
+{
+  UriList uris;
+  Q_FOREACH ( QgsLayerTreeNode* node, nodes )
+    _addLayerTreeNodeToUriList( node, uris );
+  return uriListToByteArray( uris );
+}
+
 QString QgsMimeDataUtils::encode( const QStringList& items )
 {
   QString encoded;
@@ -141,3 +186,15 @@ QStringList QgsMimeDataUtils::decode( const QString& encoded )
   return items;
 }
 
+
+QByteArray QgsMimeDataUtils::uriListToByteArray( const QgsMimeDataUtils::UriList& layers )
+{
+  QByteArray encodedData;
+
+  QDataStream stream( &encodedData, QIODevice::WriteOnly );
+  Q_FOREACH ( const Uri& u, layers )
+  {
+    stream << u.data();
+  }
+  return encodedData;
+}

src/core/qgsmimedatautils.h

@@ -19,6 +19,7 @@
 #include <QStringList>
 
 class QgsLayerItem;
+class QgsLayerTreeNode;
 
 /** \ingroup core
  * \class QgsMimeDataUtils
@@ -62,9 +63,16 @@ class CORE_EXPORT QgsMimeDataUtils
 
     static UriList decodeUriList( const QMimeData* data );
 
+    /**
+     * Returns encoded URI list from a list of layer tree nodes.
+     * @note added in QGIS 3.0
+     */
+    static QByteArray layerTreeNodesToUriList( const QList<QgsLayerTreeNode*>& nodes );
+
   private:
     static QString encode( const QStringList& items );
     static QStringList decode( const QString& encoded );
+    static QByteArray uriListToByteArray( const UriList& layers );
 
 };