Re: COLOR_PAIRS on Fedora 29

[Bryan Christ]

Ya.  After giving some more thought to it yesterday, I've decided to run with a long or a int32_t and casting where necessary.  Is it reasonable to say that down the road, the *opts arg will be the favored interface?

On Wed, Jan 16, 2019 at 7:42 PM Thomas Dickey <address@hidden> wrote:

On Wed, Jan 16, 2019 at 05:43:00PM -0600, Bryan Christ wrote:
> Timothy,
>
> Thanks for that explanation.  It sounds like the right thing to do is to
> switch over to an unsigned short and handle the nuances of values greater
> than 0x7FFF.

not quite - extended color pairs are an "int" (usually bigger than a "short").
(the same applies for extended color values)

> On Wed, Jan 16, 2019 at 5:18 PM Timothy Allen <address@hidden> wrote:
>
> > On Wed, 2019-01-16 at 10:20 -0600, Bryan Christ wrote:
> > > I'm debugging an issue on Fedora 29.  The terminfo value for pairs on
> > > xterm-256color is set to 0x10000 which is in the range of an unsigned
> > > short but not a short.  Isn't this problematic since most the ncurses
> > > APIs like wattr_set() expect a short?
> >
> > In the ncurses 5 ABI, the terminfo database file-format uses signed
> > shorts for everything, so values are clamped at 0x7FFF even if
> > logically they should be higher.
> >
> > In the ncurses 6 ABI, the terminfo database file-format has been
> > extended to allow larger numbers, so values generally do not need to be
> > clamped.
> >
> > For example, the new "xterm-direct" terminal description (xterm with
> > 24-bit colour) reports colors=0x1000000, although it still has
> > pairs=0x10000 because the actual number of possible pairs is a 49-bit
> > number, and ncurses *can't* allocate that many pairs just for memory-
> > allocation reasons.
> >
> > As for wattr_set(), the manpage says:
> >
> > > Each of the functions added by XSI Curses has a parameter opts,
> > > which X/Open Curses still  (after  more  than twenty  years)
> > > documents as reserved for future use, saying that it should be
> > > NULL.  This implementation uses that parameter in ABI 6 for the
> > > functions which have a color-pair parameter to support extended
> > > color pairs:
> > >
> > > •   For functions which modify the color, e.g., wattr_set, if opts
> > >     is set it is treated as a pointer to  int, and used to set the
> > >     color pair instead of the short pair parameter.
> >
> > > I could simply change my code to an unsigned short, but i'm not sure
> > > what that would do to ncurses.  Alternatively, I could simply
> > > redefine COLOR_PAIRS to 0x7FFF which is what Bionic Beaver uses.  As
> > > best I can tell, it looks like Fedora 29 made a poor decision.
> >
> > The current Debian Testing uses the ncurses 6 ABI, as does Ubuntu
> > Cosmic, so it's not just Fedora 29.
> >
> >
> > _______________________________________________
> > Bug-ncurses mailing list
> > address@hidden
> > https://lists.gnu.org/mailman/listinfo/bug-ncurses
> >
>
>
> --
> Bryan
> <><

--
Thomas E. Dickey <address@hidden>
https://invisible-island.net
ftp://ftp.invisible-island.net

--

Bryan
<><