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131 lines
4.1 KiB
C#
131 lines
4.1 KiB
C#
// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
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// See the LICENCE file in the repository root for full licence text.
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using System;
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using System.Collections.Generic;
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using System.IO;
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using System.Linq;
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using osu.Framework.Bindables;
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using osu.Framework.Extensions;
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namespace osu.Game.Screens.Edit
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{
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/// <summary>
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/// Tracks changes to the <see cref="Editor"/>.
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/// </summary>
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public abstract partial class EditorChangeHandler : TransactionalCommitComponent, IEditorChangeHandler
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{
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public readonly Bindable<bool> CanUndo = new Bindable<bool>();
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public readonly Bindable<bool> CanRedo = new Bindable<bool>();
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public event Action? OnStateChange;
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private readonly List<byte[]> savedStates = new List<byte[]>();
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private int currentState = -1;
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/// <summary>
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/// A SHA-2 hash representing the current visible editor state.
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/// </summary>
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public string CurrentStateHash
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{
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get
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{
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ensureStateSaved();
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using (var stream = new MemoryStream(savedStates[currentState]))
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return stream.ComputeSHA2Hash();
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}
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}
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private bool isRestoring;
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public const int MAX_SAVED_STATES = 50;
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public override void BeginChange()
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{
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ensureStateSaved();
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base.BeginChange();
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}
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private void ensureStateSaved()
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{
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if (savedStates.Count == 0)
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SaveState();
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}
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protected override void UpdateState()
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{
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if (isRestoring)
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return;
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using (var stream = new MemoryStream())
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{
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WriteCurrentStateToStream(stream);
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byte[] newState = stream.ToArray();
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// if the previous state is binary equal we don't need to push a new one, unless this is the initial state.
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if (savedStates.Count > 0 && newState.SequenceEqual(savedStates[currentState])) return;
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if (currentState < savedStates.Count - 1)
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savedStates.RemoveRange(currentState + 1, savedStates.Count - currentState - 1);
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if (savedStates.Count > MAX_SAVED_STATES)
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savedStates.RemoveAt(0);
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savedStates.Add(newState);
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currentState = savedStates.Count - 1;
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OnStateChange?.Invoke();
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updateBindables();
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}
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}
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public void RestoreState(int direction)
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{
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if (TransactionActive)
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return;
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if (savedStates.Count == 0)
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return;
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int newState = Math.Clamp(currentState + direction, 0, savedStates.Count - 1);
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if (currentState == newState)
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return;
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isRestoring = true;
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ApplyStateChange(savedStates[currentState], savedStates[newState]);
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currentState = newState;
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isRestoring = false;
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OnStateChange?.Invoke();
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updateBindables();
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}
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/// <summary>
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/// Write a serialised copy of the currently tracked state to the provided stream.
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/// This will be stored as a state which can be restored in the future.
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/// </summary>
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/// <param name="stream">The stream which the state should be written to.</param>
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protected abstract void WriteCurrentStateToStream(MemoryStream stream);
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/// <summary>
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/// Given a previous and new state, apply any changes required to bring the current state in line with the new state.
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/// </summary>
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/// <param name="previousState">The previous (current before this call) serialised state.</param>
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/// <param name="newState">The new state to be applied.</param>
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protected abstract void ApplyStateChange(byte[] previousState, byte[] newState);
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private void updateBindables()
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{
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CanUndo.Value = savedStates.Count > 0 && currentState > 0;
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CanRedo.Value = currentState < savedStates.Count - 1;
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}
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}
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}
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