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You can safely explore alternative ideas on a diagram because you can always revert to a prior state by undoing the changes. You can also redo those undone changes, so you're able to flip back and forth between older and more recent incarnations of a diagram without losing any information.
Every change you make in a diagram is recorded in the command history for easy undoing.
Note however that a diagram's command history is not retained between editing sessions : the command history will be empty when you load a diagram. It will also be empty when you create a new diagram.
You can view the contents of the command history in the 'History' window.
The command history records the various changes you've made to the diagram and enables you to undo and/or redo those changes :
To undo a change to the diagram you can either
- Select 'Undo' from the 'Edit' menu
- Press CTRL-Z
- Press the 'Undo' button in the 'History' window, if showing
To redo a previously undone change to the diagram, either
- Select 'Redo' from the 'Edit' menu
- Press CTRL-Y
- Press the 'Redo' button in the 'History' window, if showing
The command history is basically a chronologically ordered list of changes that were made to the diagram since it was created or loaded (whichever came last). With each position in that list corresponds a certain revision of the diagram. Likewise, the current state of the diagram corresponds to a position in the list (usually the last position, i.e. the revision with most recent change).
The following table lists how various actions influence the command history and the current position therein :
Action |
Effect on command history |
|---|---|
| undo | move current position in command history to previous entry, if any |
| redo | move current position in command history to next entry, if any |
| edit diagram | Each change to the diagram is recorded as a separate entry in the command history. When you make a change, first all changes from command history that are more recent than the one in the current position are removed. After that, the change appended to the history. |
| edit text | When you finish editing an element's text, first all changes from the command history that are more recent than the one in the current position are rmoved. Only then is the text change appended to the history. |
| new diagram | clear command history |
| load diagram | clear command history |