Re: ruler support in hexl mode

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

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

> > 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):
> 
> Hey neat.  When was this added?
> 
> >   (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))
> 
> Note that if there's no margin (i.e. 99% of the time) this will not align
> things properly on a text terminal.  This is the reason why I do
> a `make-string' for the leading space: the size of the string is used
> for alignment in text-terminals while the `display' prop is used otherwise.

Clever!  I didn't consider that.

> 
> Of course, the text-terminal display engine should ideally be improved to
> understand :align-to and such things, but I won't be the one to implement it.

I can give it a try.

> 
> Also, how about adding a `text-start' special case which would stand for
> (+ (scroll-bar . left) left-fringe left-margin) so that we don't have to
> remember all the possible display elements and so that when we decide to
> add yet another display element we won't have to update the code.

That's a good idea.  I'll do that.

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