Re: (type graphic)

[Eli Zaretskii]

> From: Miles Bader <address@hidden>
> Date: Thu, 26 Oct 2000 06:46:14 +0900 (JST)
> > 
> > If there are other reasons for the distinction between display types 
> > inside defface, let's hear them.
> 
> Ok, off the top of my head:
> 
>   * Underline    [graphic: always yes, tty: if has TC entry]
>   * Italic       [graphic: always yes, tty: not on any model I know]
>   * Boxes        [graphic: always yes, tty: prob always no]
>   * Font sizes   [graphic: always yes, tty: prob always no]
>   * Font weights [graphic: mostly yes, tty: if has TC entry, usally only bold]
>   * Variant widths [graphic: mostly yes, tty: almost always no, or TC entry]
>   * Overline     [graphic: always yes, tty: prob always no]
>   * Strike thru  [graphic: always yes, tty: prob always no]
>   * # of Colors  [graphic & tty have similar issues, but this could
>                   be thought of as being under the `class' tag, not the
>                   `type' tag]
> 
> You can see there's an obvious pattern above...  So (type graphic/tty)
> *does* have some meaning, until there's a better mechanism.

My comments were relevant only to the differences in color
attributes.  For the other attributes, you are right that there's a
pattern (which isn't surprising, since the attributes were modeled
after capabilities of a typical toolkit).

>   (defface my-emphasis
>     '((((supported :italic))    :slant italic)
>       (((supported :height))    :height 2.0)
>       (((supported :underline)) :underline t)
>       (t                        :inverse-video t)))

This is redundant, I think: unsupported attributes are simply ignored,
so we cannot gain too much here.  Note that Emacs deffaces almost
always use color, either together or instead of the other attributes,
so most faces will have some emphasis anyhow.  I'm not sure it's worth
the hassle to parameterize the attribute support to such a great
extent.

> As for the color-tag, I'm not sure.  How about if an argument to `color'
> is an integer, then the test succeeds when the number of supported of
> colors is >= the argument.

>From my experience, the ``knee point'' is between 16 and 256 colors.
It doesn't really matter, for the Emacs face definitions, how much
colors are supported as long as there are at least 256.  It's
certainly true for the default definitions.