undostack.cs

c#精彩编程百例（源代码）

//  UndoStack.cs 
//  Copyright (c) 2000 Mike Krueger
//
//  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

using System;
using System.Diagnostics;
using System.Collections;
using SharpDevelop.Internal.Text;

namespace SharpDevelop.Internal.Undo {
	
	/// <summary>
	/// This class implements an undo stack
	/// </summary>
	public class UndoStack
	{
		Stack undostack = new Stack();
		Stack redostack = new Stack();
		
		public event EventHandler AfterUndo;
		public event EventHandler AfterRedo;
		
		/// <summary>
		/// This property is EXCLUSIVELY for the UndoQueue class, don't USE it
		/// </summary>
		internal Stack _UndoStack {
			get {
				return undostack;
			}
		}
		
		/// <summary>
		/// You call this method to pool the last x operations from the undo stack
		/// to make 1 operation from it.
		/// </summary>
		public void UndoLast(int x)
		{
			undostack.Push(new UndoQueue(this, x));
		}
		
		/// <summary>
		/// Call this method to undo the last operation on the stack
		/// </summary>
		public void Undo()
		{
			if (undostack.Count > 0) {
				UndoableOperation uedit = (UndoableOperation)undostack.Pop();
				redostack.Push(uedit);
				uedit.Undo();
				if (AfterUndo != null)
					AfterUndo(null, null);
			}
		}
		
		/// <summary>
		/// Call this method to redo the last undone operation
		/// </summary>
		public void Redo()
		{
			if (redostack.Count > 0) {
				UndoableOperation uedit = (UndoableOperation)redostack.Pop();
				undostack.Push(uedit);
				uedit.Redo();
				if (AfterRedo != null)
					AfterRedo(null, null);
			}
		}
		
		/// <summary>
		/// Call this method to push an UndoableOperation on the undostack, the redostack
		/// will be cleared, if you use this method.
		/// </summary>
		public void Push(UndoableOperation operation) 
		{
			if (operation == null)
				throw new ArgumentNullException("UndoStack.Push(UndoableOperation operation) : operation can't be null");
			
			undostack.Push(operation);
			ClearRedoStack();
		}
		
		/// <summary>
		/// Call this method, if you want to clear the redo stack
		/// </summary>
		public void ClearRedoStack()
		{
			redostack.Clear();
		}
	}
}