Re: using glyphs by default in perl-mode

[Ted Zlatanov <tzz@lifelogs.com>]

On Fri, 07 Jun 2013 10:36:24 +0300 Eli Zaretskii <eliz@gnu.org> wrote: 

>> "If it is a vector or list, it is a sequence of alternate characters and
>> composition rules, where (2N)th elements are characters and (2N+1)th
>> elements are composition rules to specify how to compose (2N+2)th
>> elements with previously composed N glyphs."
>> 
>> I stared at this for a while then I gave up.  It really needs one or two
>> examples and an alternate wording, because I have no idea what it says.)

EZ> There's a reference to reference-point-alist, which I think has those
EZ> details.

EZ> As for examples, you can see them in tv-util.el, for example.

OK, but read that sentence again.  Can you really make sense of it?

It needs rewording and an inline example right after this paragraph.  It
doesn't have to be a complicated example.

>> It would be really nice to be able to [...] use an image to create a
>> glyph.

EZ> I don't understand this: Emacs _can_ display an image, so what can you
EZ> possibly mean by "use an image to create a glyph"?  What is a "glyph"
EZ> in this context?

Currently, AFAIK Emacs treats images as a text property.  This is
convenient but there are many cases where I'd rather have images behave
like typed characters: one image == one character == one glyph.  I
proposed using a virtual, dynamically generated font outside Unicode or
perhaps in a reserved Unicode space.

The result should be that asking (just an example, not an implementation
suggestion):

(make-char 'image "/tmp/gnus.png")

will produce something that respects font size, can be scaled, and looks
like a character to all Emacs functions but like an image visually.  In
text mode or without image support it would be treated like a character
that can't be rendered.

I hope that explains things better.

Ted