RE: Integer & glyph (trunk and emacs_unicode)

[Drew Adams]

> > (defun make-glyph-code (char &optional face)
> >   "Return a glyph code representing char CHAR with face FACE."
> >   ;; Due to limitations on Emacs integer values, faces with
> >   ;; face id greater that 4091 are silently ignored.
> >   (if (and face (<= (face-id face) #xfff))
> >       (logior char (lsh (face-id face) 19))
> >     char))
>
> > So, it assumes 12 bits for face id and 19 bits for char code,
> > the result is an integer of 31 bits.
>
> I suspect that the "19" used to be something else (e.g. 16 when
> integers were 28bits, so 16+12=28).
>
> In any case, the test should be made more robust by not assuming
> anything about the available range of integers (which has changed over
> the years and can change depending on your config).
> How 'bout
>
>    (let ((id (and face (face-id face)))
>      (if (and (numberp id)
>               ;; Due to limitations on Emacs integer values, only
>               ;; face ids below a certain limit can be used.
>               (= id (lsh (lsh id 19) -19)))
>          (logior char (lsh id 19))
>        char))

I'm not really following this, but is this about the change from `19' to
`22' in this code (this is my own version, to accommodate both the old and
new)?

(defun make-glyph-code (char &optional face)
  "Return a glyph code representing char CHAR with face FACE."
  (if face
      (logior char (lsh (face-id face)
                        (if (<= emacs-major-version 22) 19 22)))
    char))

That is, is this related to thread "bug of display-table & make-glyph-code,
2007-09-10?