Please describe the problem:
After sending CSR so that the final line in the terminal is excluded from the
scroll region, glitches can occur when interspersing writes to the bottom line
with scrolls of the upper region.
Steps to reproduce:
I will attach a script (scr-fix-min) that produces the problem for me.
NOTE: This script expects LINES and COLUMNS to be exported and refer to the number of
lines and columns in your terminal. These must be accurate or the bug won't be
shown. If they are unset, you will get a ton of errors, rather than the
simulation. If one is running bash, then
$ export COLUMNS LINES
$ ./scr-fix-min
will probably work. Otherwise, COLUMNS and LINES may need to be set explicitly before running the script.
Actual results:
What I currently see: one or both of "foo" and "bar" are missing. Or, on at
least one system, the bar will be black/empty when it ought to be
reversed/have-text.
Actually, when I _should_ see "foo" and "bar", but don't, I will sometimes
actually see an effect such that it looks like the top one or two pixel-rows of
the bottom line update and switch back, but not the rest of the line. So a
masking problem or incorrect information about what portions of the display to
update seem likely.
Expected results:
What you ought to see: the bottom bar flash between "x", "foo", "x", and "bar".
Does this happen every time?
This reproduces reliably for me on gnome-terminal. xfce4-terminal sometimes
shows both "foo" and "bar" as it ought to, and sometimes doesn't (same app,
same instance, different runs of script).
Other information:
This behavior was discovered while I was using screen, which can use the final
line as a "status" line. I was playing with screen's "autoaka" feature, which
allows the current screen window's name to change based on the
currently-running command: I found that everything worked as it should until
the prompt reached the bottom, so that hitting enter caused scrolling. At that
point, the window title would stop updating.
See also the bugtracker for GNU Screen, where I discovered and analyzed the problem.
https:/