Re: New function css-color (accompanying x11-color) (issue 570690043 by address@hidden)

[Urs Liska]

Am 04.06.19 um 00:13 schrieb address@hidden:
> https://codereview.appspot.com/570690043/diff/564820043/scm/color.scm
> File scm/color.scm (right):
>
> https://codereview.appspot.com/570690043/diff/564820043/scm/color.scm#newcode678 
>
> scm/color.scm:678: (define css-color-list
> Is there anything new in this list or are all entries always alias?

I checked and saw that the following CSS colors are *not* in the X11 list:

CSS Color names not defined in X11 colors:

aqua

crimson

fuchsia

indigo

lime

olive

rebeccapurple

silver

teal

*Most* of the others are basically defined identical, with the 
differences being rounding errors. However, there are a number of real 
differences, AFAICS it's the discrepancies described in 
https://en.wikipedia.org/wiki/X11_color_names#Clashes_between_web_and_X11_colors_in_the_CSS_color_scheme 


> ...
> Ofcourse this leads to identical definitions for css-color and x11-color
> and x11-color would return a color even for p.e. Darkblue (wrongly
> cased).
> I can't imagine a problem, though

I'm not totally sure about the best way to proceed here. I agree that 
it's not a terrific idea to duplicate all those color definitions.

However, especially given the number of differences there should be 
explicit access methods for both color models. What might be a 
reasonable approach is:

 * Have one long list of shared color definitions, basically the
   existing one plus entries for the list above (I assume we can ignore
   the rounding errors issue)
 * For each color model have a list of *names* and a list (doesn't have
   to be a *separate* list) of definitions for colors that don't match
   the shared-colors list. For X11 this would *only* be the names list.
   (The determination of colors that need special definitions should be
   done once during development, not at runtime.)
 * When asking for a color it is first checked if it is in the color
   model's extension list, then in the shared list (and then fall back
   to black)
 * Given that the X11 colors Wikipedia entry states that the
   capitalization of X11 color names isn't handled consistently I
   suggest that we totally ignore casing (keep the CamelCase names in
   the manual but state that colors can be requested case insensitively)

What do you think?
Urs