Re: Issue using more than 255 color pairs

[Bill Gray]

On 7/16/23 04:35, Thomas Dickey wrote:

> Rather than using the SVr4-compatible "attron", if you were using a terminal
> description with more than 256 colors (such as xterm-direct), then the X/Open
> interfaces using cchar_t rather than chtype would help:
>
>         int attr_get(attr_t *attrs, short *pair, void *opts);
>         int wattr_get(WINDOW *win, attr_t *attrs, short *pair, void *opts);
>         int attr_set(attr_t attrs, short pair, void *opts);
>         int wattr_set(WINDOW *win, attr_t attrs, short pair, void *opts);

   And it's documented.  From :

https://invisible-island.net/ncurses/man/curs_attr.3x.html

"Color pair values can only be OR'd with attributes if the pair number 
is less than 256.  The alternate functions such as color_set can pass a 
color pair value directly."

   Looking a few lines above that paragraph reminded me of some things 
I've occasionally wondered about but never got around to asking.  From 
the same URL:

   "The XSI standard extended conformance level adds new highlights 
A_HORIZONTAL,  A_LEFT,  A_LOW,  A_RIGHT, A_TOP, A_VERTICAL (and 
corresponding WA_ macros for each).  As of August 2013, no known 
terminal provides these highlights."

   Does that mean "some terminal(s) once did provide these highlights, 
but they're all obsolete/missing as of August 2013"?  Or "Somebody might 
someday provide them,  but they haven't been yet"?

   Is there any difference intended between A_UNDERLINE and A_LOW?

   Is A_HORIZONAL basically 'strikeout'?  And what are A_VERTICAL and 
A_PROTECT supposed to be?

   I'd think the intended display characteristics might have been 
described it the XSI Curses standard, Issue 4,  but I can't seem to find 
that on-line.

Thanks!           -- Bill