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As is the case with the clipboard, the implementation of Undo and Redo functionality can be quite a challenge. In order to avoid a confusing user experience, an Undo/Redo framework has the following properties:
- Undo/Redo is restricted to the layer I'm currently working on and
- it offers a preview of the actions being undone or redone.
Undo/Redo is restricted to a layer
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The action history thus could be cleared whenever a safe point is reached. Possible safe points are:
- a page is activated: the action history is reset prior to activation. The next undo will undo the activation, but no further undo operation is available
- changes are confirmed by explicitly creating a new version in page editing. All actions executed prior to this cannot be undone, but all previous page versions could be used to return to previous states.
Note, however, that such safe points must be rare. A safe point is typically only reached if:
- an action is executed, which can be interpreted as confirmation of all executed actions before (e.g. create new page version)
- an action is executed, which may be regarded as end of a chain of actions (e.g. activating a page or starting a work flow)
In particular, the following actions do not represent a safe point:
- changing to a different menu item in AdminCentral (e.g. leaving website for asset management)
- leaving one layer for another one e.g. leave AdminCentral for page editing: the action history of the first layer is still preserved and shall be available again when you quit page editing.
Possible conflicts
Note that having multiple layers leads conflicts between layers. If you e.g. add a page and start editing it, but then switch back to the layer you added the page in and delete the page, the page editing layer is taken the very foundation it works on. Currently, this leads to an exception and an error message indicating that the page was probably deleted, moved or renamed. Likewise, undoing an action in one layer could lead to problems in another layer (e.g. undoing the add page in the example above would also cause problems in page editing).
Possible conflict resolutions could be:
- showing an error message in the layer that detected the problem (the solution applied today)
- locking content a layer works on and preventing deleting, moving or renaming any such locked content. A warning message would be shown instead.
Using Undo/Redo
Please consult the usage summary for a full definition of mouse, touch and keyboard usage definitions.
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