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Undo and History

In this example, we will show you how to use the CreativeEditor SDK’s CreativeEngine to undo and redo steps in the editor API.

Functions

fun createHistory(): History
  • Brief: Create a history which consists of an undo/redo stack for editing operations.

There can be multiple. But only one can be active at a time.

  • Returns the handle to the created history.
fun destroyHistory(history: History)

Destroy the given history, returns an error if the handle doesn’t refer to a history.

  • history: the history to be destroyed.
fun setActiveHistory(history: History)

Mark the given history as active, returns an error if the handle doesn’t refer to a history.

All other histories get cleared from the active state. Undo/redo operations only apply to the active history.

  • history: the history to be marked as active.
fun getActiveHistory(): History

Get the handle to the currently active history. If there’s none it will be created.

  • Returns the handle to the active history.
fun addUndoStep()

Adds a new history state to the stack, if undoable changes were made.

fun undo()

Undo one step in the history if an undo step is available.

fun canUndo(): Boolean

If an undo step is available.

  • Returns true if an undo step is available.
fun redo()

Redo one step in the history if a redo step is available.

fun canRedo(): Boolean

If a redo step is available.

  • Returns true if a redo step is available.
fun onHistoryUpdated(): Flow<Unit>

Subscribe to changes to the undo/redo history.

  • Returns flow of history updates.

Full Code

Here’s the full code:

// Manage history stacks
val newHistory = engine.editor.createHistory()
val oldHistory = engine.editor.getActiveHistory()
engine.editor.setActiveHistory(newHistory)
engine.editor.destroyHistory(oldHistory)


engine.editor.onHistoryUpdated()
    .onEach { println("Editor history updated") }
    .launchIn(CoroutineScope(Dispatchers.Main))


// Push a new state to the undo stack
engine.editor.addUndoStep()


// Perform an undo, if possible.
if (engine.editor.canUndo()) {
    engine.editor.undo()
}


// Perform a redo, if possible.
if (engine.editor.canRedo()) {
    engine.editor.redo()
}