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Undo / Redo

julieb
julieb asked
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Last Modified: 2013-11-20
I am implementing a graphical newtork editor in Visual C++ 5.0 running on the Windows NT 4.0 platform. This editor should support multiple undo / redo functionality.

I have looked in all available MFC / OLE / COM books and in the online help in DevStudio and the only information I have found has been the manual pages for:
      IOleUndoManager
      IOleUndoUnit
      IOleParentUndoUnit

In my opinion these man pages are very difficult to understand especially since no examples are included with them.

Is there anyone out there who can give me any information and perhaps examples on how undo / redo is best implemented using MFC.
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Commented:
Trap undo/redo keys and handle them yourself. For contained OLE objects, just pump the keyboard input to them.
Tommy HuiEngineer

Commented:
The concept of undo and redo was hard for me to understand until I read that the state of the application is captured by the undo and redo.

For example, let's say that you want to create a graphical editor that lets you draw lines and circles and such. So when a user draws a line, you catch the difference of the state of the application before and after drawing that line and store that within an object and store that object within a list (because you want to support more than one level of undo). Then if the user decides to undo that line, the object knows what was affected by that line and restores everything back. Of course, if the user wants to redo, the object is still in the list and knows how to put the line back.

If you want to read more about undo/redo objects, I recommend you pick up the book Design Patterns by Gamma et al. It is a really good book on designing applications with C++.

Author

Commented:
No pointers on how to implement Undo / Redo best in MFC

Commented:
Check http://web.ukonline.co.uk/Members/julian.smart/code.html. You can find sample code there called "Command/Undo"
Commented:
This one is on us!
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