Re: Issue using more than 255 color pairs

[Bill Gray]

Hi Mike,

On 7/17/23 23:13, Mike Gran wrote:
> 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

   Hmmm... so if you apply A_VERTICAL to a fullwidth character that 
would 'normally' be horizontal,  it's rotated 90 degrees clockwise; 
apply A_HORIZONTAL to a fullwidth character that's normally 
vertically-oriented,  and it's rotated 90 degrees counterclockwise;  in 
both cases,  A_LOW, A_LEFT, A_RIGHT, and A_TOP are similarly rotated. 
(I can't see what A_HORIZONTAL and A_VERTICAL would do for halfwidth 
text.  Possibly,  if you had two halfwidth characters in a row with 
A_VERTICAL,  they'd both get rotated,  first one appearing above the 
second.)

   Also,  addch( A_VERTICAL | (fullwidth character)) should cause the 
cursor to drop one line instead of advancing two columns.

   This all does sound plausible,  though as you say,  it'll probably 
remain guesswork unless someone who was in on the writing of those specs 
steps forward to set the record straight.

Thanks!       -- Bill

> 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