Reorganise intervals by drag and drop

The interval view now allows the user to drag and drop intervals
up and down in the list.

We could extend the drag and drop of intervals to support analysis
of segments/intervals from multiple rides in the future too.

Fixes #405.

src/IntervalTreeView.cpp

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2012 Damien Grauser (Damien.Grauser@pev-geneve.ch)
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include "IntervalTreeView.h"
+#include "IntervalItem.h"
+#include "MainWindow.h"
+
+
+IntervalTreeView::IntervalTreeView(MainWindow *mainWindow) : mainWindow(mainWindow)
+{
+    setDragDropMode(QAbstractItemView::InternalMove);
+    setDragDropOverwriteMode(true);
+    setDropIndicatorShown(true);
+    invisibleRootItem()->setFlags(Qt::ItemIsSelectable | Qt::ItemIsEnabled);
+}
+
+void
+IntervalTreeView::dropEvent(QDropEvent* event)
+{
+    IntervalItem* item1 = (IntervalItem *)itemAt(event->pos());
+    QTreeWidget::dropEvent(event);
+    IntervalItem* item2 = (IntervalItem *)itemAt(event->pos());
+
+    if (item1==topLevelItem(0) || item1 != item2)
+        QTreeWidget::itemChanged(item2, 0);
+}