TextTreeUndo.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / System / Windows / Documents / TextTreeUndo.cs / 1 / TextTreeUndo.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// 
// Description: Helper class for TextContainer, handles all undo operations. 
//
// History: 
//  03/03/2004 : [....] - Created
//
//---------------------------------------------------------------------------
 
using MS.Internal.Documents;
 
namespace System.Windows.Documents 
{
    // This static class is logically an extension of TextContainer.  It contains 
    // TextContainer undo related helpers.
    internal static class TextTreeUndo
    {
        //----------------------------------------------------- 
        //
        //  Internal Methods 
        // 
        //-----------------------------------------------------
 
        #region Internal Methods

        // Adds a TextTreeInsertUndoUnit to the open parent undo unit, if any.
        // Called from TextContainer.InsertText and TextContainer.InsertEmbeddedObject. 
        internal static void CreateInsertUndoUnit(TextContainer tree, int symbolOffset, int symbolCount)
        { 
            UndoManager undoManager; 

            undoManager = GetOrClearUndoManager(tree); 
            if (undoManager == null)
                return;

            undoManager.Add(new TextTreeInsertUndoUnit(tree, symbolOffset, symbolCount)); 
        }
 
        // Adds a TextTreeInsertElementUndoUnit to the open parent undo unit, if any. 
        // Called from TextContainer.InsertElement.
        internal static void CreateInsertElementUndoUnit(TextContainer tree, int symbolOffset, bool deep) 
        {
            UndoManager undoManager;

            undoManager = GetOrClearUndoManager(tree); 
            if (undoManager == null)
                return; 
 
            undoManager.Add(new TextTreeInsertElementUndoUnit(tree, symbolOffset, deep));
        } 

        // Adds a TextTreePropertyUndoUnit to the open parent undo unit, if any.
        // Called by TextElement's property change listener.
        internal static void CreatePropertyUndoUnit(TextElement element, DependencyPropertyChangedEventArgs e) 
        {
            UndoManager undoManager; 
            PropertyRecord record; 
            TextContainer textContainer = element.TextContainer;
 
            undoManager = GetOrClearUndoManager(textContainer);
            if (undoManager == null)
                return;
 
            record = new PropertyRecord();
            record.Property = e.Property; 
            record.Value = e.OldValueSource == BaseValueSourceInternal.Local ? e.OldValue : DependencyProperty.UnsetValue; 

            undoManager.Add(new TextTreePropertyUndoUnit(textContainer, element.TextElementNode.GetSymbolOffset(textContainer.Generation) + 1, record)); 
        }

        // Adds a DeleteContentUndoUnit to the open parent undo unit, if any.
        // Called by TextContainer.DeleteContent. 
        internal static TextTreeDeleteContentUndoUnit CreateDeleteContentUndoUnit(TextContainer tree, TextPointer start, TextPointer end)
        { 
            UndoManager undoManager; 
            TextTreeDeleteContentUndoUnit undoUnit;
 
            if (start.CompareTo(end) == 0)
                return null;

            undoManager = GetOrClearUndoManager(tree); 
            if (undoManager == null)
                return null; 
 
            undoUnit = new TextTreeDeleteContentUndoUnit(tree, start, end);
 
            undoManager.Add(undoUnit);

            return undoUnit;
        } 

        // Adds a TextTreeExtractElementUndoUnit to the open parent undo unit, if any. 
        // Called by TextContainer.ExtractElement. 
        internal static TextTreeExtractElementUndoUnit CreateExtractElementUndoUnit(TextContainer tree, TextTreeTextElementNode elementNode)
        { 
            UndoManager undoManager;
            TextTreeExtractElementUndoUnit undoUnit;

            undoManager = GetOrClearUndoManager(tree); 
            if (undoManager == null)
                return null; 
 
            undoUnit = new TextTreeExtractElementUndoUnit(tree, elementNode);
 
            undoManager.Add(undoUnit);

            return undoUnit;
        } 

        // Returns the local UndoManager. 
        // Returns null if there is no undo service or if the service exists 
        // but is disabled or if there is no open parent undo unit.
        internal static UndoManager GetOrClearUndoManager(ITextContainer textContainer) 
        {
            UndoManager undoManager;

            undoManager = textContainer.UndoManager; 
            if (undoManager == null)
                return null; 
 
            if (!undoManager.IsEnabled)
                return null; 

            if (undoManager.OpenedUnit == null)
            {
                // There's no parent undo unit, so we can't open a child. 
                //
                // Clear the undo stack -- since we depend on symbol offsets 
                // matching the original document state when an undo unit is 
                // executed, any of our units currently in the stack will be
                // corrupted after we finished the operation in progress. 
                undoManager.Clear();
                return null;
            }
 
            return undoManager;
        } 
 
        #endregion Internal methods
    } 
}


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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