Re: cursor doesn't show through transparent images in emacs 22, unlike emacs 21

["Ken Manheimer" <ken.manheimer@gmail.com>]

On 8/25/06, Richard Stallman <rms@gnu.org> wrote:
>     > as i think i suggested in a previous message, the solution i would
>     > prefer would be to have some way to qualify icons so that they get a
>     > solid cursor in their transparent areas, and the default would be to
>     > have it inactive.  eg, a qualifier for xpm, png, gif, and other
>     > transparent-capable images, like :solid-cursor:
>     >
>     > `:solid-cursor-shows BOOLEAN'
>     >       When true, the cursor will appear solid through the transparent
>     > regions of the image
>
> This does not make sense without more context.  For instance, what
> behavior would a value of nil specify?  And what happens in
> non-transparent regions of the image?

i was using it only to elaborate certain details of my suggestion, not
as the real documentation.  as such, it was meant specifically for
those following the context.

non-transparent regions seems like a complicated issue.  i expect that
in many cases it's neither desirable nor practial to mess with them.
some systems xor the colors under mouse icons, for instance, but
there's no reason to expect the chosen colors would be particularly
harmonious, or the icon to even be recognizable with such treatment.
however, there's a bind for icons with no transparency - hopefully the
highlighted bounding box cursor is sufficient there.

> Meanwhile, something about this wording bothers me: the idea that the
> cursor appears "through" part of the image.  Is this based on the
> assumption that the image is "on top of" the cursor?

i could as easily have said that the cursor shows "in" the transparent
parts of the image, leaving the opaque parts undisturbed.

> If so, I think that assumption is backwards and must be changed.  The
> cursor is "on top of" the image; if we want to display a cursor on the
> image, the image should not be allowed to block it out!

i think we're on pretty safe ground doing having the opaque parts o
the image block out the cursor.

consider text characters - cursors being on the character could simply
block them from view, reinforcing the paradigm of being on top of the
character.  that's a terrible loss of information - generally, the
character is allowed to show through.  the character might be shown in
the inverse tone of the cursor, or some chosen color, or something.
(emacs goes with a chosen color, i guess.)

the situation with glyphs is not so simple, because they can have
many, arbitrary colors.  in my particular case, having the cursor show
in the transparent region has the outline-structure bullet icons and
guide lines acting very like elaborate text characters, except that
their intricately colored opaque parts are not changed.  it works
well.

-- 
ken
ken.manheimer@gmail.com
http://myriadicity.net