Undo and Redo

The Undo and Redo functionality has been exposed to PML, so you can create your own set of undoable events.

There are several ways AVEVA E3D adds entries to the undo system:

• Using the MARKDB / ENDMARKDB commands. The syntax is as follows: MARKDB 'text', where text is an optional description to be included with the mark. This causes a mark to be made in the database and an entry made in the undo stack. You should make their database changes, and then use the command ENDMARKDB.

• By creating a PML undoable object and adding it to the undo stack. For a fuller description of this object, refer to the Software Customization Reference documentation. You should create an undoable object, set up the undo and redo execution strings, and then call the method add() to mark the database and add the undoable to the undo stack. Make the database changes, and then call the method endUndoable().

• Automatically whenever a model element is moved using graphical interaction techniques in Model Editor.

Additionally, you may register to be informed whenever an undo or redo operation has taken place, using the PML PostEvents object. For a fuller description of this object, refer to the Software Customization Reference documentation.

After an undoable has been removed from the stack and its state recovered, then your supplied method on the PostEvents object is called, and will be passed the description text that was associated with the undoable object.