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
Namespace: Unity.AppUI.Undo
Assembly: solution.dll
Syntax
public class UndoStack

Constructors

Name Description
UndoStack()

Default constructor.

Properties

Name Description
this[int]

Gets the command at the given index.
canRedo

Weather the redo stack is empty.
canUndo

Weather the undo stack is empty.
cleanIndex

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

The whole commands list.
count

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

The index of the last command in the undo stack.
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.
lastCommand

The last command in the undo stack.
memorySize

The total memory size of the undo stack.
undoLimit

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

Methods

Name Description
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);
Clear()

Clears the undo and redo stacks.
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.
Push(UndoCommand)

Pushes the given command on the undo stack.
Redo()

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

Sets the clean state to -1.
SetClean()

Sets the clean state to the last command in the undo stack.
Undo()

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

Events

Name Description
cleanStateChanged

Emitted when the clean state changes.
indexChanged

Emitted the current Command index changes.