This sounds lame, but, despite what I said above, there are cases where undo/redo is just too complicated or impossible – real-time operating system scenarios, modifications to data that are subsequently acted upon, and so on.Ģ. There are three ways that developers handle undo/redo:ġ. Undo/redo is actually pretty darn easy to implement, particular in this case where a cell has a binary value (either it gets set or reset – there’s no ambiguity). It turns out that I mostly did well in the last post, but in order to accommodate the undo/redo in an elegant way, I needed to make minor changes to the ToggleCell() method as well as to the mouse event handlers. It particularly requires me to think hard about modular code, because I don’t know precisely what I’ll be writing in blogpost n + 1, and yet I have to show code in blogpost n and I don’t want there to have to be major changes in methods that I’ve already posted. (For example, the Euchre game that I blogged about was something I’d written a couple of years ago, so there were no surprises for me when writing the posts about it.) As such, for this series I’m spending a lot more time documenting what my thoughts are while coding than I normally do, and it’s very interesting have that all down in print. This is the first application that I’ve built specifically for this blog, where I’m actually writing the code while I’m writing the blog.
MPS moves the caret before each step of undo/redo, and then performs the Undo/Redo actions.(This is the second part in my series on creating a Paint-by-Numbers designer application.) When you undo or redo a complex operation, MPS requests for your confirmation. MPS expands the undo and redo mechanism to complex operations, such as reformatting or refactoring source code, creating or deleting files. The following events signal about the end of a logical step: MPS smartly defines the logical steps that can be undone and redone.
However, when you exit MPS, the undo history is lost. You can undo or redo your changes as many times as required. The Redo command discards the results of the last Undo command. The Undo command discards the last changes to the file in the editor.
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