Re: Help wanted with bkgd() rookie mistake

[Thomas Dickey]

On Sun, Jan 05, 2025 at 12:17:15PM -0600, G. Branden Robinson wrote:
> Hi Bill,
> 
> At 2025-01-05T13:06:31-0500, Bill Gray wrote:
> > On 1/5/25 11:23, G. Branden Robinson wrote:
> > > Hi folks,
> > > 
> > > I come once again to confess my confusion with basic curses operations.
> > > 
> > > Please find attached two C programs; I call them "bkgd" and "bkgrnd",
> > > because they correspond to curses functions of the same name.
> > > 
> > > bkgrnd, the wide-character program, works fine.
> > > 
> > > bkgd, which you'd think would be simpler, doesn't.
> > > 
> > > In both, I expect the background character to be set to an underlined @
> > > sign.
> > 
> >    I see the background as underlined @ signs with both programs.  I'm using
> > (default,  system-installed,  now getting to be elderly) ncurses
> > 6.2.20200212.  So perhaps a behavior change between then and now?
> 
> Hmm.  That may be.  I'm on the bleeding edge with 6.5.20250104.

Both programs look fine to me, but I don't replace the system (n)curses,
but rather use the test-packages whose build-scripts are in the
"packages" directory.

For those, I was testing with the wide-character library either way

bkgd:
        linux-vdso.so.1 (0x00007ffc5b99a000)
        libncursesw6.so.6 => /lib/x86_64-linux-gnu/libncursesw6.so.6 
(0x00007f43130c7000)
        libtinfow6.so.6 => /lib/x86_64-linux-gnu/libtinfow6.so.6 
(0x00007f431308c000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f4312eab000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f431313b000)
bkgrnd:
        linux-vdso.so.1 (0x00007fffd31d9000)
        libncursesw6.so.6 => /lib/x86_64-linux-gnu/libncursesw6.so.6 
(0x00007ff0cf47f000)
        libtinfow6.so.6 => /lib/x86_64-linux-gnu/libtinfow6.so.6 
(0x00007ff0cf444000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007ff0cf263000)
        /lib64/ld-linux-x86-64.so.2 (0x00007ff0cf4f3000)

and defining NCURSES_WIDECHAR when compiling.

(I have non-wide "ABI 5" libraries to verify things, but don't package those)
 
> I'll have to uninstall my ncurses and use my similarly geriatric system
> version...
> 
> ...nope, it still reproduces even after uninstalling, deleting "bkgd",
> and re-make(1)ing.
> 
> $ ldd ./bkgd
>         linux-vdso.so.1 (0x00007ffd6f0f9000)
>         libncurses.so.6 => /lib/x86_64-linux-gnu/libncurses.so.6 
> (0x00007f4be605d000)
>         libtinfo.so.6 => /lib/x86_64-linux-gnu/libtinfo.so.6 
> (0x00007f4be602e000)
>         libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f4be5e5a000)
>         libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f4be5e54000)
>         /lib64/ld-linux-x86-64.so.2 (0x00007f4be60b1000)
> $ dpkg -S /lib/x86_64-linux-gnu/libncurses.so.6
> libncurses6:amd64: /lib/x86_64-linux-gnu/libncurses.so.6
> $ dpkg -s libncurses6:amd64 | grep -i version
> Version: 6.2+20201114-2+deb11u2
> 
> The wide-character exhibit, "bkgrnd", continues to work fine, displaying
> both the "@" and an underline in every character cell.
> 
> >    However,  both PDCurses and PDCursesMod show @ with no underscore. I
> > agree that this seems wrong.
> > 
> >    (BTW,  why do you have tests for NCURSES_VERSION and NCURSES_OPAQUE?  It
> > looks to me as if you aren't using anything ncurses-specific and that your
> > code doesn't rely on opaqueness.  FWIW,  PDCursesMod has opaque window and
> > screen structures;  PDCurses doesn't.)
> 
> Sorry for the red herrings.  You're right; those preprocessor tests are
> irrelevant to this program.  It's boilerplate that I've copied among a
> bunch of little C programs I write to teach myself the library (and help
> myself to tell the truth in the man pages).

I have seen comments that ncurses-examples aren't simple...

-- 
Thomas E. Dickey <dickey@invisible-island.net>
https://invisible-island.net

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