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Modeling Menus

Undo and Redo (commands)

Step back through what you have done, and forward again.

Menu: Edit > Undo, Edit > Redo | Shortcuts: Cmd-Z, Shift-Cmd-Z

Two commands, one history, and one thing about it that surprises people: there are two histories, one per window, and the command acts on whichever window you are working in.

Undo

Takes the design back one step. A hundred steps are kept, so you can walk a long way back.

The menu item names the step it is about to take back, which is worth reading before you press it. In the model window that name comes from the action itself: Undo Move, Undo Circle, Undo Auto Region. In the node window it is worked out by comparing the node graph before and after, which gives one of six: Add Node, Delete, Connect, Disconnect, Move, Edit.

When there is nothing left to take back, the item greys out.

Undoing clears the selection. Nothing is lost by that, but if you were working on a careful selection, expect to make it again.

Redo

Puts back what you just undid, up to the same hundred steps, and names the step the same way: Redo Connect.

Redo only survives while you keep stepping. Make any new change and the redo history is discarded, because from there the steps you had undone no longer follow on from what is now on screen.

Two windows, two histories

The model window and the node window each keep their own hundred steps, and Undo applies to the window you are in. Undoing in the model window does not take back a wire you connected in the node window, and undoing in the node window does not take back a circle you drew.

That is a feature rather than an oversight: the two windows hold different work, and a single shared history would mean an undo in one undoing something you cannot see. On the desktop the menu bar shows both histories, so you can always tell what each side is holding.

What counts as one step

A step is a finished action, not a movement of the mouse. Drawing a circle by clicking a center and then a rim point is one step, not two, and dragging a point is one step however far it travels.

A click that changed nothing costs no step at all. The history is only advanced when the construction actually came out different, so a stray click on empty space does not use up an undo.

The tidying that a tool does on your behalf is part of the same step as the thing it tidied. A tool that leaves construction points behind and hides them hides them inside the same step, so one undo puts the drawing back as it was rather than leaving a scatter of stray hidden points to clean up.

What clears the history

• Opening a document, including Revert to Saved, starts a fresh history. You cannot undo past a load, and you cannot undo the load itself.
• Entering or leaving a cluster in the node window resets the node history, because the graph you are looking at is a different graph.

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Related

• Revert to Saved: the other way back, and a much bigger one.
• Two-window mode: what each window is for, which is why each keeps its own history.
• Clusters: the node window's nested graphs, and why entering one starts a new history.