Class UndoStack

An undo stack maintains a stack of commands that have been applied in your application.

New commands are pushed on the stack using Push(UndoCommand). Commands can be undone and redone using Undo() and Redo().

UndoStack keeps track of the current command. This is the command which will be executed by the next call to Redo(). The index of this command is returned by index. The state of the edited object can be rolled forward or back using index. If the top-most command on the stack has already been redone, index is equal to count.

UndoStack provides *command compression*, command *macros*, and supports the concept of a *clean state*.

Inheritance

object

UndoStack

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: Unity.AppUI.Undo

Assembly: Unity.AppUI.Undo.dll

Syntax

public class UndoStack

Constructors

UndoStack()

Default constructor.

Declaration

public UndoStack()

Properties

this[int]

Gets the command at the given index.

Declaration

public UndoCommand this[int idx] { get; }

Parameters

Type	Name	Description
int	idx	The index of the command.

Property Value

Type	Description
UndoCommand	The command at the given index, or null if the index is out of range.

canRedo

Weather the redo stack is empty.

Declaration

public bool canRedo { get; }

Property Value

Type	Description
bool

canUndo

Weather the undo stack is empty.

Declaration

public bool canUndo { get; }

Property Value

Type	Description
bool

cleanIndex

The index of the clean state. -1 if there is no clean state.

Declaration

public int cleanIndex { get; }

Property Value

Type	Description
int

commands

The whole commands list.

Declaration

public IEnumerable<UndoCommand> commands { get; }

Property Value

Type	Description
IEnumerable<UndoCommand>

count

The number of commands in the stack. Macros are counted as a single command.

Declaration

public int count { get; }

Property Value

Type	Description
int

index

The index of the last command in the undo stack.

Declaration

public int index { get; set; }

Property Value

Type	Description
int

isClean

Weather the undo stack is in a clean state. The clean state is useful when the application supports saving and restoring the state of an object.

Declaration

public bool isClean { get; }

Property Value

Type	Description
bool

lastCommand

The last command in the undo stack.

Declaration

public UndoCommand lastCommand { get; }

Property Value

Type	Description
UndoCommand

memorySize

The total memory size of the undo stack.

Declaration

public ulong memorySize { get; }

Property Value

Type	Description
ulong

undoLimit

The maximum number of memory units that can be stored in the undo stack.

Declaration

public ulong undoLimit { get; set; }

Property Value

Type	Description
ulong

Methods

BeginMacro(string)

Begins composition of a macro command with the given text description.

An empty command described by the specified text is pushed on the stack. Any subsequent commands pushed on the stack will be appended to the macro command's children until EndMacro() is called.

While a macro is being composed, the stack is disabled. This means that:
- Events are not emitted.
- canRedo and canUndo will always return false.
- Calling Undo() or Redo() has no effect.
The stack is re-enabled when the macro is ended.

Here is an example of how to use macros: undoStack.BeginMacro("Insert Red Text"); undoStack.Push(new InsertText(...)); undoStack.Push(new SetRedText(...)); undoStack.EndMacro(); This code is equivalent to: var insertRedText = new UndoCommand("Insert Text"); new InsertText(..., insertRedText); new SetRedText(..., insertRedText); undoStack.Push(insertRedText);

Declaration

public void BeginMacro(string name)

Parameters

Type	Name	Description
string	name	The name of the macro command.

Remarks

Nested calls to BeginMacro(string) are supported, but every call to BeginMacro(string) must have a corresponding call to EndMacro().

See Also

EndMacro()

Clear()

Clears the undo and redo stacks.

Declaration

public void Clear()

EndMacro()

Ends composition of a macro command.
If this is the outermost macro in a set nested macros, this function emits indexChanged once for the entire macro command.

Declaration

public void EndMacro()

Exceptions

Type	Condition
InvalidOperationException	Thrown if no macro is being composed.

See Also

BeginMacro(string)

Push(UndoCommand)

Pushes the given command on the undo stack.

Declaration

public void Push(UndoCommand command)

Parameters

Type	Name	Description
UndoCommand	command	The command to push.

Remarks

If the current command is a macro command, the pushed command is added to the macro.

Redo()

Calls Redo() on the last command in the redo stack.

Declaration

public void Redo()

ResetClean()

Sets the clean state to -1.

Declaration

public void ResetClean()

SetClean()

Sets the clean state to the last command in the undo stack.

Declaration

public void SetClean()

Undo()

Calls Undo() on the last command in the undo stack.

Declaration

public void Undo()

Events

cleanStateChanged

Emitted when the clean state changes.

Declaration

public event Action cleanStateChanged

Event Type

Type	Description
Action

indexChanged

Emitted the current Command index changes.

Declaration

public event Action<int> indexChanged

Event Type

Type	Description
Action<int>