Re: Issue using more than 255 color pairs

[Mike Gran]

On 7/16/23 15:31, William McBrine wrote:
>    Taking a look at

> https://pubs.opengroup.org/onlinepubs/7908799/xcurses/curses.h.html

 >   lists the fifteen attr_t constants as (rearranged here to put the 
> six 'highlight' attributes together) :

> WA_ALTCHARSET  Alternate character set
> WA_BLINK      Blinking
> WA_BOLD        Extra bright or bold
> WA_DIM        Half bright
> WA_INVIS      Invisible
> WA_PROTECT    Protected
> WA_REVERSE    Reverse video
> WA_STANDOUT    Best highlighting mode of the terminal
> WA_UNDERLINE  Underlining

> WA_LEFT        Left highlight
> WA_RIGHT      Right highlight
> WA_LOW        Low highlight
>WA_TOP        Top highlight
> WA_HORIZONTAL  Horizontal highlight
> WA_VERTICAL    Vertical highlight

>    which suggests to me that A_LOW isn't A_DIM and it isn't 
> A_UNDERLINE.  I'd think the six 'highlight' attributes would be similar,
> except that they 'highlight' different parts of the character cell.

Hi, as long as we're doing archaeology.
When I looked into WA_LEFT and friends before, I eventually convinced
myself that they were for Japanese characters that could run
horizontally or vertically and that could have lines above or below
horizontal characters or to the left or right of vertical characters.
My evidence was looking at the SGR escape code in JIS X 0211.

In JIS X 0211, SGR 60 through 69 seems to match these attributes.

SGR 60 is
"single line below character with horizontal line orientation 
or single line on the right side of character with vertical line orientation"
SGR 68 is "single line above character with horizontal line orientation 
or single line on the right side of character with vertical line orientation"

But that isn't "proof", of course. For proof you'd need some notes from X/Open
about what the heck they were thinking at the time.

-Mike Gran