Re: Fwd: Add support for axiterm colors in parse_color

[Jeff King <peff@peff.net>]

On Thu, Jan 09, 2020 at 07:20:09PM -0500, Eyal Soha wrote:

> > That said, I'm not entirely opposed to having more human-readable
> > aliases. I'm not sure if it's worth using the 16-color version (e.g.,
> > "ESC[91m" versus the 256-color version "ESC[38;5;9m"). It's possible it
> > would be compatible with more terminals, and it is slightly fewer bytes.
> 
> My motivation for this patch was to fix the github workflow log output
> that doesn't support 8bit colors properly.  Only the "ANSI" colors
> 0-15 worked.  None of the 8-bit colors worked except for 30-37, 40-47,
> 90-97, and 100-107, which matched the ANSI colors.  That is a very
> broken color scheme!  But that's how it displayed.

That makes sense. I'm not too surprised to see a terminal that supports
one but not the other.

But I wonder if there are ones that go the other way around: supporting
256-color mode but not ANSI 90-97, etc. I doubt it, but I think it would
be nice to split that change out into a separate commit in case we do
run into problems.

> Done.  Here's a new patch!

Thanks. The content here is looking pretty good (though I have a few
comments below).

Can you also format it as described in Documentation/SubmittingPatches
and re-send? In particular, it needs a regular commit message and your
signoff.

> +enum {
> +       COLOR_BACKGROUND_OFFSET = 10,
> +       COLOR_FOREGROUND_ANSI = 30,
> +       COLOR_FOREGROUND_RGB = 38,
> +       COLOR_FOREGROUND_256 = 38,
> +       COLOR_FOREGROUND_BRIGHT_ANSI = 90,
> +};

The split in this enum mostly makes sense to me. It changes the meaning
of "value" for COLOR_ANSI, but this is all local to color.c, so your
changes to output_color() are all that's needed.

It might be easier to follow the patch if switching to this enum came in
a separate preparatory patch.

> @@ -92,7 +100,13 @@ static int parse_color(struct color *out, const
> char *name, int len)
>         for (i = 0; i < ARRAY_SIZE(color_names); i++) {
>                 if (match_word(name, len, color_names[i])) {
>                         out->type = COLOR_ANSI;
> -                       out->value = i;
> +                       out->value = i + COLOR_FOREGROUND_ANSI;
> +                       return 0;
> +               }
> +               if (*name == '+' &&
> +                   match_word(name+1, len-1, color_names[i])) {
> +                       out->type = COLOR_ANSI;
> +                       out->value = i + COLOR_FOREGROUND_BRIGHT_ANSI;
>                         return 0;
>                 }

It would be slightly simpler and more efficient handle the "+" outside
the loop, like:

  int offset = COLOR_FOREGROUND_ANSI;
  if (*name == '+') {
          offset = COLOR_FOREGROUND_BRIGHT_ANSI;
	  name++;
	  len--;
  }

and then in the loop just set "out->value = i + offset".

You'd probably want to hoist this out to a separate function since
"name" needs to be unchanged in the later part of the function.

I dunno. It's almost certainly an unmeasurable micro-optimization, but
somehow the flow of it seems simpler to me.

I also wondered if we'd want English aliases like "brightred" that some
other systems use. It would be easy to add that to the check I showed
above without having to repeat as much.

> @@ -109,10 +123,15 @@ static int parse_color(struct color *out, const
> char *name, int len)
>                 else if (val < 0) {
>                         out->type = COLOR_NORMAL;
>                         return 0;
> -               /* Rewrite low numbers as more-portable standard colors. */
> +               /* Rewrite 0-7 as more-portable standard colors. */
>                 } else if (val < 8) {
>                         out->type = COLOR_ANSI;
> -                       out->value = val;
> +                       out->value = val + COLOR_FOREGROUND_ANSI;
> +                       return 0;
> +               /* Rewrite 8-15 as more-portable aixterm colors. */
> +               } else if (val < 16) {
> +                       out->type = COLOR_ANSI;
> +                       out->value = val - 8 + COLOR_FOREGROUND_BRIGHT_ANSI;

And I think this 8-15 handling might want to be a separate commit on
top, just because it's possible it might regress some cases (though
again, I do doubt it).

>         case COLOR_256:
> -               out += xsnprintf(out, len, "%c8;5;%d", type, c->value);
> +         out += xsnprintf(out, len, "%d;5;%d", COLOR_FOREGROUND_256 + offset,
> +                          c->value);

Looks like some unwanted tab/space conversion (here and elsewhere).

> +test_expect_success 'axiterm bright fg color' '
> +       color "+red" "[91m"

s/axi/aix/ (here and below).

> +test_expect_success '8-15 are aliases for aixterm color names' '
> +       color "12 13" "[94;105m"

Makes sense.

-Peff