Here's a thought - at some point, we expect that there will be a recording mechanism for GIMP, and when that happens, perhaps some coupling between it and the undo mechanism would help reduce some memory requirements for the undo mechanism. If we know whether a user action is deterministic, the undo action could rewind to a prior checkpoint where the image had been kept intact, and the actions since that time could be reapplied to advance up to the previous action. When a nondeterministic action occurs, a checkpoint mechanism would still need cause the image (or a portion of it) to be kept, but that would not be necessary for each step. Since creating a new layer is deterministic, deleting the layer should be able to be undone replaying the creation of the empty layer, thus, the undo action doesn't need to keep the empty layer in memory. Exceptions: Actions that take input from external sources would need to be treated like nondeterministic actions, causing a checkpoint to occur. Actions that use random numbers could record the random number seed that is used and be treated as deterministic. Just a thought... _-T ________________________________________________________________ Juno Platinum $9.95. Juno SpeedBand $14.95. Sign up for Juno Today at http://www.juno.com! Look for special offers at Best Buy stores.
