Re: MS-DOS color issues

[Eli Zaretskii]

On Sun, 28 Oct 2001, Tim Van Holder wrote:

> * What's the rationale behind using black-on-light-gray as
>   defaults for MS-DOS?  DOS is not an xterm, so it seems
>   more logical to use the normal *nix tty default (white
>   on black).  That, or using the current foreground &
>   background active in DOS.

You need to remember that until Emacs 21.1, released only a few days ago, 
Emacs didn't support colors on a Unix TTY.  So all the color defaults in 
Emacs were for X, and the X version by default comes up with a bright 
background.  So, for the default Emacs colors to look good, the MS-DOS 
version switched the terminal to black-on-lightgray.

> * rgb.txt seems to be incomplete, or the color name matching
>   routine does not match that used by X;

rgb.txt is not used for color matching.  See tty-colors.el for the actual 
list of colors used by the TTY emulation of X colors.

>   I took my GNU/Linux
>   customization settings and tried them under DOS; most
>   worked reasonably as expected, but other did not.
> 
> Examples:
>  - font-lock-comment-face was PaleViolet, but this color
>    is apparently unknown, resulting in the default
>    foreground color (white, in my case)

I need to know the RGB values of all the colors that aren't in 
tty-colors.el, and then I can add the missing ones.

(In general, I'd suggest not to use non-portable color names.)

>  - ediff's highlighting faces had their background set to
>    PaleWhite, resulting in the default background (black,
>    in my case), which in combination with 'Black' being
>    foreground color yielded unreadable text).

Well, I did tell you the Emacs defaults are not suited well to the black 
background, didn't I? ;-)

It sounds like Ediff's faces need some different defaults in the case of 
a TTY with a dark background.

>   In both cases, simply changing the color name helped,
>   but color names valid under X should be valid elsewhere
>   as well

No, that's not the intent: it's in general impossible to make sure the 
default colors are good for all possible variations of display defaults, 
especially when TTYs are concerned.  The transparent mapping of X colors 
is only supposed to show the user that there is some non-default color
here and there, but some users will _have_ to customize the colors if they 
want the display to look well.

The color defaults for the standard cases were carefully selected to work 
well on most, if not all, displays, including the TTY, but faces in 
packages such as Ediff are not guaranteed to be good for all.  Don't 
forget that the number of available colors on a standard TTY is very small.

This will probably improve with time, but I don't think it will be ever 
good for everybody; even on X some users cannot stand Emacs default faces, 
and need to customize them.

As a rule of thumb, I really suggest to use the light background mode on 
MS-DOS and TTYs.  Not only are the colors generally better thought out, 
but you have moe colors that look pleasantly on a light background than 
on a dark one.