Re: Issue using more than 255 color pairs

[Mike Gran]

Bill-

>> My evidence was looking at the SGR escape code in JIS X 0211.

>    Hmmm... an interesting thought... seems to me you may be on to something 
>here.

>    Any idea what A_VERTICAL or A_HORIZONTAL highlights would mean in this > 
>case?  And what the difference would be between A_LOW and A_UNDERLINE?

Again going with the Japanese terminal idea, my guess is that A_VERTICAL
and A_HORIZONTAL means the run direction of the text.
When Japanese is written vertically, interstitial
Latin words are written sideways,
as well as some punctuation.

Check out Figure 1 on this article as an example:
https://www.unicode.org/reports/tr50/tr50-28.html

And my guess for A_LOW vs A_UNDERLINE is the difference between
escape code SGR 4 "Singly underlined" and SGR 60 "Single line below 
character with horizontal line orientation or single line on the right
side of character with vertical line orientation".  Some related standards
like ITU-T T.101 call the SGR 60 "ideogram underline or right side line",
where "ideogram" was the common name used for kanji + hanzi at the time.

But really, it is all guesswork.

-Mike Gran