Re: ruler support in hexl mode

[storm@cua.dk (Kim F. Storm)]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> 
> > +;; This function is derived from `ruler-mode-ruler' in ruler-mode.el.
> > +(defun hexl-mode-ruler ()
> > +  "Return a string ruler for hexl mode."
> > +  (when hexl-use-ruler
> > +    (let* ((fullw (ruler-mode-full-window-width))
> > +	   (w     (window-width))
> > +	   (m     (window-margins))
> > +	   (lsb   (ruler-mode-left-scroll-bar-cols))
> > +	   (lf    (ruler-mode-left-fringe-cols))
> > +	   (lm    (or (car m) 0))
> > +	   (ruler (make-string fullw ?\ ))
> 
> We really need to move this out of ruler-mode into frame.el or some other
> "global" file.  And to give it a clean interface so its implementation can
> be improved later.

You can drop all of that ruler-mode- stuff if you use the advanced
pixel-alignment form of :align-to (see xdisp.c around line 17990):

  (let ((s " 87654321  0011 2233 4455 6677 8899 aabb ccdd eeff  0123456789abcdef")
        (pos 0))
    ;; Turn spaces in the header into stretch specs so they work
    ;; regardless of the header-line face.
    (while (string-match "[ \t]+" s pos)
      (setq pos (match-end 0))
      (put-text-property (match-beginning 0) pos 'display
                         ;; Assume fixed-size chars
                         `(space :align-to (+ (scroll-bar . left)
                                              left-fringe left-margin
                                              ,(1- pos)))
                         s))
    ;; Highlight the current column.
    (put-text-property (+ 11 (/ (* 5 highlight) 2))
                       (+ 13 (/ (* 5 highlight) 2))
                       'face 'highlight s))

> Note that the use of the display property also allows us to deal with
> fractional sizes, although lsb and lf don't take advantage of it yet.

The above code snippet does exact pixel alignment !

> Also I wish we could put some more useful info up there, but admittedly,
> I can't think of any.


-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk