randy@uw-june.UUCP (William Randy Day) (07/04/87)
I seem to have found an annoying screen update bug in GNU emacs.
The symptoms are: when the terminal's baud rate is 1200 or slower, and
an incremental search searches ahead to something off the screen,
the screen is messed up when it tries to update to the new
position.
Typically, emacs will display two status lines, one positioned
normally at the bottom of the screen, and the other positioned two lines
above. The line in between usually is where the cursor is positioned,
and it is usually the line with the search target or one line after the
search targe.
The bug occurs in versions 18.45, 18.32, and 17.63 with vt100,
z29, and kermit emulating h19 or vt100 terminals. Interestingly, there
is one exeception: a real vt100 terminal and version 17.63 work properly.
(At least for my test case.)
The problem seems to be emac's screen update algorithm. At 9600 baud
it decides it's faster to just redraw the screen. At 1200 baud it
tries to do some scrolling and line insertions, which are not
done correctly.
Randy Day.
Internet (ARPA): randy@dbnet.cs.washington.edu
CSNET: randy%washington@relay.cs.net
UUCP: {decvax|ihnp4}!uw-beaver!uw-june!randyrandy@uw-june.UUCP (William Randy Day) (07/04/87)
Opps... Forget the reported bug. I'm red in the face. Seems my preceived bug is really a feature. Randy