Re: Exceeding COLORS

[Bryan Christ]

Timothy,

Thanks for the clarification.  In anticipation of that all being the case, I've already started thinking about carving out color matches to nearest "color blocks".  Again, thank you.

On Thu, Jan 30, 2020 at 5:48 PM Timothy Allen <address@hidden> wrote:

I think there might be some confusion here.

Firstly, no, you can't exceed COLORS. If your terminal emulator wants to support direct-color mode when the outer terminal is 256-color, you'll just have to round each color to the nearest entry in the 256-color palette, like tmux does. Just because *your* 256-color terminal happens to also support direct-color mode doesn't mean that every 256-color terminal does.

Secondly, xterm-direct operates very differently from traditional paletted-color modes like xterm-256color, and your code probably won't handle it properly unless you manually update it. For example, xterm-direct cannot modify its "palette"; if you want to draw text in colour #AABBCC, you can't call init_color() or init_extended_color(), you just create a pair and pass it color 0xAABBCC (assuming 24-bit direct-color, see the "RGB" capability in user_caps(5) for details). See this previous thread for direct-color details: https://lists.gnu.org/archive/html/bug-ncurses/2018-04/msg00011.html

On 31/1/20 3:15 am, Bryan Christ wrote:

Thomas,

So I'm a bit more confused now.  I am using extended_color_content() and as soon as "int color" is > 255 the function returns ERR.  I did a simple test with "xterm-direct" and it still doesn't matter.  The debug code snippet in question is this:

retval = extended_color_content(color, r, g, b);

if(retval == ERR) { endwin(); fprintf(stderr, "gc %d\n\r", color); exit(0); }

As soon as the variable "color" becomes 256 it fails returning ERR.  It's behavior seems identical to what is described for the standard color_content() API for which the man pages says:

The first argument must be a legal color  value,  i.e.,  0  through COLORS-1, inclusive.

The man pages really don't say anything about extended_color_content() other than it uses int instead of short.  So why is it rejecting a color value of 256 even when TERM is set to xterm-direct?

I am encountering this with the distro included version of ncurses on Fedora 31.

On Wed, Jan 29, 2020 at 5:53 PM Thomas Dickey <address@hidden> wrote:

On Wed, Jan 29, 2020 at 03:21:21PM -0600, Bryan Christ wrote:
> When ncurses starts up, I know that it looks at the value of "colors" from
> the terminfo entry and sets COLORS accordingly.  However, I also know that
> the underlying terminal supports way more colors and pairs than is
> advertised by the terminfo entry.  Is there a way to forcibly exceed that
> limit?  The following script runs great on the native terminal, but as soon
> as I run in my emulator, under the confines of ncurses, I hit a 256 color
> wall.
>
> !/bin/bash
> awk 'BEGIN{
>     s="/\\/\\/\\/\\/\\"; s=s s s s s s s s;
>     for (colnum = 0; colnum<77; colnum++) {
>         r = 255-(colnum*255/76);
>         g = (colnum*510/76);
>         b = (colnum*255/76);
>         if (g>255) g = 510-g;
>         printf "\033[48;2;%d;%d;%dm", r,g,b;
>         printf "\033[38;2;%d;%d;%dm", 255-r,255-g,255-b;
>         printf "%s\033[0m", substr(s,colnum+1,1);
>     }
>     printf "\n";
> }'

I suspect the issue to resolve is in your emulator - ncurses 6.1 can
_show_  2^24 colors using the xterm-direct terminal description
(though it requires some work to map to/from the different representations),
but it won't show 2^24 colors using xterm-256color

Using the full range of colors requires the *_extended functions,
as I did in picsmap:

https://github.com/ThomasDickey/ncurses-snapshots/blob/master/test/picsmap.c

e.g., these

extern NCURSES_EXPORT(int) init_extended_color(int, int, int, int);
extern NCURSES_EXPORT(int) init_extended_pair(int, int, int);

and the functions where an "opts" parameter was reserved to be null:

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

--
Thomas E. Dickey <address@hidden>
https://invisible-island.net
ftp://ftp.invisible-island.net

--

Bryan
<><

--

Bryan
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