From Preamble:
"Change Set: MouseMoveEvtStartPos-ar Date: 18 August 2003 Author: Eddie Cottongim
Fixes a bug where MouseMoveEvents would not report their startPosition correctly. Change by Andreas Raab."
To observe this bug, execute "HandMorph showEvents: true" and observe the starting point for mouse moves. Its usually wrong - most of the time, start point = end point. It makes much more sense after the patch.
The change makes sense to me. startPosition is now set to the hand's current position. Since the hand hasn't yet been moved in response to the event being formed, it makes sense that the hand's current position will the the starting point for the next mouse move event.
Someone should see if this helps/hurts Genie - Genie uses the start position for mouse moves. I'm suprised it would work at all given the old, broken behavior.
Thanks, Eddie