On Fr, 10 Jan 2014, Bram Moolenaar wrote:
> Christian Brabandt wrote:
>
> > On Di, 07 Jan 2014, Matteo Cavalleri wrote:
> >
> > > some easy steps to reproduce the problem:
> > >
> > > :set t_Co?
> > > t_Co=256
> > > :set background?
> > > background=light
> > > :set background=dark
> > > :set background?
> > > background=dark
> > > :hi Normal ctermfg=grey ctermbg=234
> > > :set background?
> > > background=light
> > > :hi Normal ctermfg=grey ctermbg=0
> > > :set background?
> > > background=dark
> >
> > > as you can see, the "hi" command changes background to light when
> > > ctermbg is set to 234, however, according to
> > > http://upload.wikimedia.org/wikipedia/commons/9/95/Xterm_color_chart.png
> > > color 234 is indeed a dark grey
> >
> > I see the problem:
> >
> > 7728 if (color >= 0)
> > 7729 {
> > 7730 if (termcap_active)
> > 7731 term_bg_color(color);
> > 7732 if (t_colors < 16)
> > 7733 i = (color == 0 || color == 4);
> > 7734 else
> > 7735 i = (color < 7 || color == 8);
> > 7736 /* Set the 'background' option if the value is
> > 7737 * wrong. */
> > 7738 if (i != (*p_bg == 'd'))
> > 7739 set_option_value((char_u *)"bg", 0L,
> > 7740 i ? (char_u *)"dark"
> > 7741 : (char_u *)"light", 0);
> > 7742 }
> >
> > i.e. Vim always sets a light background for all colors except the first
> > 7 and color 8 for which it will set a dark background. I don't think Vim
> > should try to determine what color is used and depending on it's value
> > try to set a sane 'bg' value for the other 256 colors (in a 256 color
> > terminal or the 88 rxvt color cube) so for now, I would propose to
> > adjust the logic only slightly to something like this:
> >
> > diff --git a/src/syntax.c b/src/syntax.c
> > --- a/src/syntax.c
> > +++ b/src/syntax.c
> > @@ -7731,6 +7731,14 @@
> > term_bg_color(color);
> > if (t_colors < 16)
> > i = (color == 0 || color == 4);
> > + else if (t_colors == 256)
> > + {
> > + i = (color < 7 || color == 8 ||
> > + (color > 231 && color < 244));
> > + if (i > 16 && i < 232)
> > + i = (*p_bg == 'd');
> > + }
> > +
> >
> > Which means only for the lower 12 (dark) gray colors (232 until 243) in
> > the 256 color cube set the 'bg' to dark, for all other (except the ones
> > mentioned above) leave the bg setting alone.
>
> It's a start. However, if we change this we might as well do it
> properly.
>
> In my opinion we should take the color chart and compute the brightness
> of each color. If it's above 50% 'background' should be set to light.
>
> There at least is this image:
> http://upload.wikimedia.org/wikipedia/en/thumb/1/15/Xterm_256color_chart.svg/2000px-Xterm_256color_chart.svg.png
>
> A list of #RGB values could be used to compute the brightness.
How about the attached patch? For colors > 15, it uses the rxvt color
cube for 88 color terminals and the xterm color cube for 256 color
terminals and computes the luminance. If the luminance is above a
certain treshhold, it uses a light background, else it uses a dark
background.
It uses the same logic, that I have been using for my Colorizer plugin
(https://github.com/chrisbra/color_highlight) for which I haven't seen
any complaints about the luminance yet (of course this doesn't mean this
is correct by all means).
Best,
Christian
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diff --git a/src/syntax.c b/src/syntax.c
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -7731,6 +7731,51 @@
term_bg_color(color);
if (t_colors < 16)
i = (color == 0 || color == 4);
+ else if (color >= 16 && t_colors == 88) /* rxvt color cube */
+ {
+ int r = 0;
+ int g = 0;
+ int b = 0;
+ int colorcube[4] = {0x00, 0x8B, 0xCD, 0xFF};
+ int luminance;
+
+ if (color >= 16 && color < 80)
+ {
+ color -= 16;
+ r = colorcube[(color / 16) % 4];
+ g = colorcube[(color / 4) % 4];
+ b = colorcube[color % 4];
+ }
+ else if (color >= 80)
+ {
+ color -= 80;
+ r = g = b = 46.36 + (float)color * 23.18 + (color > 0 ? 23.18 : 0.0);
+ }
+ luminance = 30 * r + 59 * g + 11 * b;
+ i = (luminance <= 12000);
+ }
+ else if (color >= 16 && t_colors == 256) /* xterm color cube */
+ {
+ int r = 0;
+ int g = 0;
+ int b = 0;
+ int colorcube[6] = {0x00, 0x5F, 0x87, 0xAF, 0xD7, 0xFF};
+ int luminance;
+
+ if (color >= 16 && color < 232)
+ {
+ color -= 16;
+ r = colorcube[(color / 36) % 6];
+ g = colorcube[(color / 6) % 6];
+ b = colorcube[color % 6];
+ }
+ else if (color >= 232)
+ r = g = b = 8 + (color - 232) * 0x0a;
+
+ luminance = 30 * r + 59 * g + 11 * b;
+ i = (luminance <= 12000);
+ }
+
else
i = (color < 7 || color == 8);
/* Set the 'background' option if the value is
