Undo

Click the Edit | Undo command, press CTRL+Z or click the button to reverse the last operation performed. If the last operation cannot be reversed, the Undo command is not available. After you close a file, the undo operations are cleared, so you cannot undo any operations performed before the file was closed. After you have undone an operation, the Edit | Redo command becomes highlighted, allowing you to reverse the just completed Undo command.

Undo Levels

Up to 100 undo levels can be set though Tools | Options | General. Enter a value between zero and 100 in the Undo Levels box.

Undo Limitations

Some actions cannot be reversed with the Undo command, including rotations, operations performed with a dragger, transparency changes, and Tools | Options commands. Undo is grayed after selecting these commands.

Using the Undo command with a Colormap is a special condition. When selecting Undo after altering a Colormap, all changes made in the Colormap are undone, reverting back to the original condition before the Colormap Editor dialog was opened.

Using the Undo command with the Auto Update box unchecked is a special condition. When selecting Undo with the Auto Update box unchecked, you still need to press the Update Now button or choose the Network | Update Network command to show the change made after selecting Undo.