On Wed, May 13, 2026 at 09:42:12PM -0400, Frank Palazzolo wrote: > Hello, > > I discovered an issue with ncurses on Slackware, both version 6.3 used in > Slackware 15.0 and 6.6 used in Slackware-current. I was testing a real > serial terminal - a Tandy DT-1 set to emulate a tvi910.
tvi910|TeleVideo model 910,
am, msgr,
cols#80, it#8, lines#24, xmc#1,
^^^^^
bel=^G, cbt=\EI, clear=^Z, cr=\r, cub1=^H, cud1=\n, cuf1=^L,
cup=\E=%p1%' '%+%c%p2%' '%+%c, cuu1=^K, ed=\EY, el=\ET,
home=\E=^A^A, hpa=\E]%p1%' '%+%c, ht=^I,
if=/usr/local/ncurses/share/tabset/stdcrt, ind=\n,
invis@, kbs=^H, kcub1=^H, kcud1=\n, kcuf1=^L, kcuu1=^K,
kf0=^AI\r, kf1=^A@\r, kf2=^AA\r, kf3=^AB\r, kf4=^AC\r,
kf5=^AD\r, kf6=^AE\r, kf7=^AF\r, kf8=^AG\r, kf9=^AH\r,
khome=^^, rev=\EG4, rmso=\EG0, rmul=\EG0, sgr0=\EG0,
smso=\EG4, smul=\EG8, vpa=\E[%p1%' '%+%c,
>
> It turns out that, for all ncurses apps, with TERM=tvi910 I get a bunch of
> spaces being printed all the time, instead of optimized cursor movement. I
> tried the same configuration on Debian 13 (trixie) as well as arch, and
> these work fine. So I started to suspect the issue is something specific
> to the configure options used by Slackware. I tested some other terminal
> types, vt100 and adm3a, and they seem to be unaffected.
>
> I have written a trivial test program here:
> https://github.com/palazzol/ncurses_test
> And, I think I have narrowed it down to the configure option
> --enable-wmc-glitch option, which Slackware uses. It seems like this
--enable-xmc-glitch
Compile-in support experimental xmc (magic cookie) code.
^^^^^^^^^^^^
> causes the bad behavior with this terminal type. If I rebuild ncurses
> without that, everything works fine.
>
> Is this kind of dramatic failure expected when using that option? I see it
> is marked as "experimental". I'm honestly not sure if my trace has
> captured the root cause yet, but you can see that the test program
> generates <100 bytes when working properly, or >2K bytes when not.
I'd expect xmc-glitch to do "something" if there were video attributes,
and otherwise not much (and your example doesn't do that), so it sounds
like code rot which I can probably fix. It's been a long time since that
feature was changed - from trying to get some clone of hpterm to run :-(
--
Thomas E. Dickey <[email protected]>
https://invisible-island.net
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