Re: gamegrid.el and some games

[Richard Stallman <rms@gnu.org>]

    Pardon my ignorance: what happens with colour images on monochrome
    displays? Are they displayed in shades of gray if
    `display-grayscale-p' returns [non-]nil?

I don't know.  Gerd, can you answer?

    Are there any displays for which `display-images-p' returns t, but
    both `display-color-p' and `display-grayscale-p' return nil? Is it
    necessary to make sure that gamegrid.el DTRT on such displays?

There certainly WERE computers whose displays could only show black
and white.  Using X on those displays, it would be proper for
display-images-p to return t and the other two to return nil.

It is possible that no such displays have been built in recent years.
gamegrid.el should do SOME kind of Right Thing on those displays, but
pretending they cannot draw images might be good enough.

    If not, I suggest to simply convert XPMs via some Lisp functions if
    Emacs is compiled without XPM-support on the C-level. I have written a
    prototype[1] for this. What do you think?

Converting XPM to PPM seems useful, because with this, we can arrange
that Emacs can always display XPM format.  That makes the API specs
simpler.  It would be nice if Emacs always used this conversion method
when you try to display an XPM and the support is not built in.

But why do you prefix this with "if not"?  I know very very little
about these graphics formats, so it isn't obvious to me why this
method would depend on being able to display more than just black and
white.  Can you explain?