ipad onscreen drawing undo issue

I'm developing an ipad on screen drawing application using openGL. I was able to program the drawing part but don't know how to create th开发者_开发技巧e undo action.

simply I want to undo one by one(painted parts) by clicking the undo button. I'm using EAGLContext to draw on the screen.

Please help me to solve the problem.

Thank you

Hassy.

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It's mostly up to you. You should use NSUndoManager to manage this, but you're free to set up your undo/redo actions as you wish.