Hello,

My application includes a drawing feature and I would like the add the
ability to "undo". The undo feature currently in place simply loads
the bitmap from the last saved file, so no matter how many changes
they make to their drawing "undo" will revert it back to the way it
was before any changes were made.

What I want to do now is make it more like the "undo" feature we are
used to in modern applications, so that it does not go back to the way
the file was when we first opened it, rather it goes back in various
steps during our editing (which can be quite numerous).

My idea is to save the current bitmap in a linked list after every
occurrence of finger down, finger up. Thus every time the user lifts
their finger from the screen the bitmap will be added to the linked
list. Then of course when "undo" is selected the bitmap at the top of
the stack will be loaded. The only problem is if the user makes 20,
30, 40+ changes to their drawing that is a lot of bitmaps to keep
references to, am I right? I see out of memory errors coming. Any
ideas for alternatives?

Thank you!

Matt.

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