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Timing bug in C-V, M-V
- To: GLS at MIT-AI
- Subject: Timing bug in C-V, M-V
- From: Mike McMahon <MMCM at MIT-AI>
- Date: Mon ,7 Jul 80 16:45:00 EDT
- Cc: BUG-ZWEI at MIT-AI
Date: 7 JUL 1980 1531-EDT
From: GLS at MIT-AI (Guy L. Steele, Jr.)
The C-V (Next Screen) and M-V (Previous Screen) commands have a severe bug.
If you type them ahead, then they perform relative to the last screen display
rather than to what the screen would be after the preceding command.
I have fixed C-V and friends to call the correct (new) primitive for first making sure point is
on the screen the way redisplay would first.
I would surmise that ZWEI is checking for typeahead for immediate eecution
before updating its idea of what ought to be on the screen. This idea
of where the screen-window into the buffer is within the buffer should be
updated even though none of it has a chance to actually be put up on the
screen. That is, ZWEI needs two ideas of what is going on--what IS on
the screen, and what OUGHT to be (but is not necessarily)--and the second
should be updated with higher priority than processing typeahead if C-V
is to work properly without timing screws like this one.
Maintenance of that much information would be much too costly, and mostly useless. In this
case, all that is important is where the window starts.