AllowCaretOutsideSelection() public method

Temporarily allows positioning the caret outside the selection. Dispose the returned IDisposable to revert the allowance.
The text area only forces the caret to be inside the selection when other events have finished running (using the dispatcher), so you don't have to use this method for temporarily positioning the caret in event handlers. This method is only necessary if you want to run the WPF dispatcher, e.g. if you perform a drag'n'drop operation.
public AllowCaretOutsideSelection ( ) : IDisposable
return IDisposable
TextArea Class Documentation
Example #1
0
        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();
                    }
                }
            }
        }