void StartDrag()
{
// prevent nested StartDrag calls
mode = SelectionMode.Drag;
// mouse capture and Drag'n'Drop doesn't mix
textArea.ReleaseMouseCapture();
DataObject dataObject = textArea.Selection.CreateDataObject(textArea);
DragDropEffects allowedEffects = DragDropEffects.All;
var deleteOnMove = textArea.Selection.Segments.Select(s => new AnchorSegment(textArea.Document, s)).ToList();
foreach (ISegment s in deleteOnMove)
{
ISegment[] result = textArea.GetDeletableSegments(s);
if (result.Length != 1 || result[0].Offset != s.Offset || result[0].EndOffset != s.EndOffset)
{
allowedEffects &= ~DragDropEffects.Move;
}
}
object dragDescriptor = new object();
this.currentDragDescriptor = dragDescriptor;
DragDropEffects resultEffect;
using (textArea.AllowCaretOutsideSelection()) {
var oldCaretPosition = textArea.Caret.Position;
try {
Debug.WriteLine("DoDragDrop with allowedEffects=" + allowedEffects);
resultEffect = DragDrop.DoDragDrop(textArea, dataObject, allowedEffects);
Debug.WriteLine("DoDragDrop done, resultEffect=" + resultEffect);
} catch (COMException ex) {
// ignore COM errors - don't crash on badly implemented drop targets
Debug.WriteLine("DoDragDrop failed: " + ex.ToString());
return;
}
if (resultEffect == DragDropEffects.None)
{
// reset caret if drag was aborted
textArea.Caret.Position = oldCaretPosition;
}
}
this.currentDragDescriptor = null;
if (deleteOnMove != null && resultEffect == DragDropEffects.Move && (allowedEffects & DragDropEffects.Move) == DragDropEffects.Move)
{
bool draggedInsideSingleDocument = (dragDescriptor == textArea.Document.UndoStack.LastGroupDescriptor);
if (draggedInsideSingleDocument)
{
textArea.Document.UndoStack.StartContinuedUndoGroup(null);
}
textArea.Document.BeginUpdate();
try {
foreach (ISegment s in deleteOnMove)
{
textArea.Document.Remove(s.Offset, s.Length);
}
} finally {
textArea.Document.EndUpdate();
if (draggedInsideSingleDocument)
{
textArea.Document.UndoStack.EndUndoGroup();
}
}
}
}