Thanks for this Rami,

I've being itching to get 24 bit colors in terminal emacs for years.

​

On Sun, Feb 12, 2017 at 8:05 AM, Rami Ylimäki <rami.ylimaki@vincit.fi>
wrote:

> From: Rami Ylimäki <rjy@iki.fi>
>
> ITU-T T.412 9.1.4 and ITU-T T.416 13.1.8 specify control function for
> changing terminal foreground and background colors. One possible format
> for the control function parameters is: 2:n:r:g:b, where 2 is color
> access mode indicating direct RGB space, n is an indentifier that gives
> detailed information about the color space and r, g, b are the color
> values.
>
> Most 24-bit terminals implement this function as 2;r;g;b. Color space
> identifier has been omitted because of its complexity and rgb values are
> assumed to be in range 0-255. Parameters are separated by semicolons
> instead of colons for historical reasons.
>
> The terminfo database supports only indexed color control functions and
> can't be used to determine whether a terminal has implemented direct
> color control functions.
>
> However, this can be worked around by creating user defined functions
> for setting 24-bit foreground and background colors. This can be done by
> creating a terminfo source file with the required capabilities and
> compiling a custom terminal type definition.
>
> For example:
>
>   $ cat xterm-24bit
>
>   # Replace semicolons with colons in setab24 and setaf24 on terminals
>   # that use ITU-T separators (iTerm2). A 24-bit integer (p1) is given
>   # as a parameter to the control functions which calculate rgb
>   # component values with following formulas:
>   # r = p1 / 65536, g = (p1 / 256) & 255, b = p1 & 255
>   xterm-24bit|xterm with 16777216 colors,
>     use=xterm-256color,
>     setab24=\E[48;2;%p1%{65536}%/%d;%p1%{256}%/%{255}%&%d;%p1%{255}%&%dm,
>     setaf24=\E[38;2;%p1%{65536}%/%d;%p1%{256}%/%{255}%&%d;%p1%{255}%&%dm,
>
>   $ tic -x -o ~/.terminfo xterm-24bit
>
>   $ TERM=xterm-24bit emacs
>
> * src/term.c (init_tty): Use 24-bit terminal colors if corresponding
> foreground and background functions are present in terminal type
> definition.
> * src/tparam.h: Define prototype for tigetstr.
> ---
>  src/term.c   | 14 ++++++++++++++
>  src/tparam.h |  4 ++++
>  2 files changed, 18 insertions(+)
>
> diff --git a/src/term.c b/src/term.c
> index b0ff9cb..9d1c3c1 100644
> --- a/src/term.c
> +++ b/src/term.c
> @@ -4131,6 +4131,20 @@ use the Bourne shell command 'TERM=...; export
> TERM' (C-shell:\n\
>
>        tty->TN_max_colors = tgetnum ("Co");
>
> +#if TERMINFO
> +      /* Non-standard support for 24-bit colors. */
> +      {
> +       const char* fg = tigetstr ("setaf24");
> +       const char* bg = tigetstr ("setab24");
> +       if (fg && bg && fg != (char *)-1 && bg != (char *)-1)
> +         {
> +           tty->TS_set_foreground = fg;
> +           tty->TS_set_background = bg;
> +           tty->TN_max_colors = 16777216;
> +         }
> +      }
> +#endif
> +
>        tty->TN_no_color_video = tgetnum ("NC");
>        if (tty->TN_no_color_video == -1)
>          tty->TN_no_color_video = 0;
> diff --git a/src/tparam.h b/src/tparam.h
> index 15664d6..8e34c9e 100644
> --- a/src/tparam.h
> +++ b/src/tparam.h
> @@ -36,4 +36,8 @@ extern char PC;
>  extern char *BC;
>  extern char *UP;
>
> +#if TERMINFO
> +char *tigetstr(const char *);
> +#endif
> +
>  #endif /* EMACS_TPARAM_H */
> --
> 2.7.4
>
>
>