QListView subclass to provide drag-n-drop in the legend

git-svn-id: http://svn.osgeo.org/qgis/trunk@291 c8812cc2-4d05-0410-92ff-de0c093fc19c

src/qgslegendview.cpp

@@ -0,0 +1,84 @@
+//
+//
+// C++ Implementation: $MODULE$
+//
+// Description: Subclassed QListView that handles drag-n-drop for changing layer order
+//
+//
+// Author: Steve Halasz <stevehalasz at users.sourceforge.net>, (C) 2003
+//
+// Copyright: See COPYING file that comes with this distribution
+//
+//
+#include <qapplication.h>
+#include <qdragobject.h>
+#include <qlistview.h>
+#include <qpoint.h>
+
+#include "qgslegendview.h"
+
+QgsLegendView::QgsLegendView( QWidget *parent, const char *name ):QListView( parent, name ), mousePressed( FALSE )
+{
+	setAcceptDrops( TRUE );
+	viewport()->setAcceptDrops( TRUE );
+}
+
+void QgsLegendView::contentsDragEnterEvent( QDragEnterEvent* e )
+{
+	QString text;
+	if ( QTextDrag::decode(e, text) ) {
+		// verify text is 'legend-drag' to avoid
+		// handling regular text drops
+		if ( text.compare("legend-drag") == 0 ) {
+			e->accept( TRUE );
+		}
+	}
+}
+
+void QgsLegendView::contentsDropEvent(QDropEvent* e)
+{
+	QString text;
+	if ( QTextDrag::decode(e, text) ) {
+		// verify text is 'legend-drag' to avoid
+		// handling regular text drops
+		if ( text.compare("legend-drag") == 0 ) {
+			QListViewItem *item = itemAt( contentsToViewport(e->pos()) );
+			// insert item in motion after one it was dropped on
+			movingItem->moveItem( item );
+			emit zOrderChanged(this);
+		}
+	} else {
+		e->ignore();
+		return;
+	}
+}
+		
+void QgsLegendView::contentsMousePressEvent( QMouseEvent* e )
+{
+	QListView::contentsMousePressEvent( e );
+	QPoint p( contentsToViewport( e->pos() ) );
+	QListViewItem *i = itemAt( p );
+	if ( i ) {
+		presspos = e->pos();
+		mousePressed = TRUE;
+	}
+}
+
+void QgsLegendView::contentsMouseMoveEvent( QMouseEvent* e )
+{
+	if ( mousePressed && ( presspos - e->pos() ).manhattanLength() > QApplication::startDragDistance() ) {
+		mousePressed = FALSE;
+		QListViewItem *item = itemAt( contentsToViewport(presspos) );
+		if ( item ) {
+			movingItem = item;
+			// create drag object with some useless text
+			QDragObject *d = new QTextDrag( "legend-drag", this );
+			d->drag();
+		}
+	}
+}
+
+void QgsLegendView::contentsMouseReleaseEvent( QMouseEvent * )
+{
+	mousePressed = FALSE;
+}

src/qgslegendview.h

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+//
+//
+// C++ Interface: $MODULE$
+//
+// Description: Subclassed QListView that handles drag-n-drop for changing layer order
+//
+//
+// Author: Steve Halasz <stevehalasz at users.sourceforge.net>, (C) 2003
+//
+// Copyright: See COPYING file that comes with this distribution
+//
+//
+#include <qlistview.h>
+
+class QgsLegendView : public QListView
+{
+	Q_OBJECT
+	
+public:
+	QgsLegendView( QWidget *parent=0, const char *name=0 );
+	
+protected:
+	// override these to provide drag-n-drop
+	void contentsDragEnterEvent( QDragEnterEvent *e );
+	void contentsDropEvent( QDropEvent *e );
+	void contentsMouseMoveEvent( QMouseEvent *e );
+	void contentsMousePressEvent( QMouseEvent *e );
+	void contentsMouseReleaseEvent( QMouseEvent *e );
+	
+signals:
+	// broadcast that the stacking order has changed
+	// so the map canvas can be redrawn
+	void zOrderChanged( QgsLegendView *lv );
+	
+private:
+	// location of mouse press
+	QPoint presspos;
+	// keep track of if the mouse is pressed or not
+	bool mousePressed;
+	// keep track of the Item being dragged
+	QListViewItem *movingItem;
+};