How would I implement undo in an OpenGL ES painting application on the iPhone?

Question

I\'m using Apple\'s sample application GLPaint as a basis for an OpenGL ES painting application, but I can\'t figure out how to implement undo functionality within it.

Answer 1

Either you can use NSUndoManager, class provided by iOS

Or you can save current state of screen area by:

CGContextRef current = UIGraphicsGetCurrentContext();

You can have one array as stack with screen image objects and on undo action you can pop value from stack and on each change push value into the stack.