Undo, redo, and the undo history

Sonar provides very powerful Undo and Redo commands that let you move forward or backward through any portion of an editing session. Every project has its own independent undo history. This means you can return to any open project and use the Undo and Redo commands, even if you’ve spent the last hour working on a different project. The undo history of a project is lost when you close the project.

Remembering everything that is necessary to undo the changes you have made can use a lot of memory. If a change you are about to make requires too much memory and cannot be undone, you will be advised that the operation is too big to undo later and asked if you want to go ahead anyway. If you do choose to perform the operation, you will not be able to undo it. Therefore, you may want to save your project first.

The Edit > History command displays a complete history of the commands and actions you can undo for the current project. The Undo History dialog box looks like this:

Figure 176. The Undo History dialog box.

A. Most recent change B. Click to clear the undo history C. Adjust the number of steps you can undo

The History command is grayed out until you make a change to the current project that can be undone.

The History list is updated every time you make a change to a project. For example, if you insert a new note into a project using the Piano Roll view, that action is added to the History list. This entry remains on the list—even if you undo the change—so that you can redo the change later on. If you delete the note, this change is added to the History list.

You can click the Clear button in the Undo History dialog box to erase the undo history for the current project and free up some memory. If Sonar is low on memory, it may offer to erase the History list. To revert to an earlier version of a project, highlight the entry in the History list that represents the point to which you’d like to return, and click OK. Sonar performs the necessary undo or redo actions to take you to that point. Once you edit the project (for example, by inserting a note), the History list is truncated at that point. Then, as you do further work, the History list grows again. Any events occurring before the event you highlighted remain on the list.

By default, Sonar keeps a history of up to 128 editing actions for each open project. Once that limit is reached, each new action pushes out the oldest item from the History list. You can raise or lower that number in the Undo History dialog box.