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.

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.