101 lines
2.6 KiB
C#
101 lines
2.6 KiB
C#
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using System.Collections.Generic;
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namespace Unity.PlasticSCM.Editor.UI.UndoRedo
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{
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internal class UndoRedoHelper
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{
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internal interface IUndoRedoHost
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{
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UndoRedoState UndoRedoState { get; set; }
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}
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internal bool CanUndo
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{
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get { return mCurrentNode != null && mCurrentNode.Previous != null; }
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}
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internal bool CanRedo
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{
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get { return mCurrentNode != null && mCurrentNode.Next != null; }
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}
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internal UndoRedoHelper(IUndoRedoHost host)
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{
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mHost = host;
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}
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internal bool TryGetLastState(out UndoRedoState state)
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{
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state = null;
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if (!IsInLastState)
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return false;
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state = mCurrentNode.Value;
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return true;
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}
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internal void UpdateLastState()
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{
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UpdateLastState(mHost.UndoRedoState);
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}
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internal void Undo()
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{
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if (mCurrentNode != null && mCurrentNode.Previous != null)
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{
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mCurrentNode = mCurrentNode.Previous;
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mHost.UndoRedoState = mCurrentNode.Value;
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}
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}
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internal void Redo()
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{
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if (mCurrentNode != null && mCurrentNode.Next != null)
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{
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mCurrentNode = mCurrentNode.Next;
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mHost.UndoRedoState = mCurrentNode.Value;
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}
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}
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internal void Snapshot()
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{
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UndoRedoState current = mHost.UndoRedoState;
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if (mCurrentNode == null || !mCurrentNode.Value.Equals(current))
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{
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if (mCurrentNode != null && mCurrentNode.Next != null)
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DiscardRedo();
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mStates.AddLast(current);
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mCurrentNode = mStates.Last;
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if (mStates.Count > UNDO_LIMIT)
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mStates.RemoveFirst();
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}
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}
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bool IsInLastState
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{
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get { return mCurrentNode != null && mCurrentNode.Next == null; }
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}
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void UpdateLastState(UndoRedoState state)
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{
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if (mStates.Last != null)
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mStates.Last.Value = state;
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}
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void DiscardRedo()
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{
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while (mCurrentNode != null && mCurrentNode.Next != null)
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mStates.Remove(mCurrentNode.Next);
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}
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LinkedListNode<UndoRedoState> mCurrentNode;
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readonly IUndoRedoHost mHost;
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readonly LinkedList<UndoRedoState> mStates = new LinkedList<UndoRedoState>();
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const int UNDO_LIMIT = 250;
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}
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}
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