Hi Eli,

Attached is a v2 patch (for discussion, not yet finished) that
demonstrates the approach. Examples of what works and what doesn't:

;; single spec, list of specs, vector of specs all work now
  (insert (propertize "foo" 'display '(right-fringe left-arrow warning
"right tooltip")))foo
  (insert (propertize "foo" 'display '((left-fringe right-arrow
warning "left tooltip"))))foo
  (insert (propertize "foo" 'display '[(right-fringe left-arrow
warning "right tooltip")]))

;; overlays with display props also work
  (overlay-put
   (make-overlay 1 2)
   'display `(left-fringe right-arrow warning "left tooltip"))

;; overlays with zero length DO NOT work (and provide no fringe indicators)
  (overlay-put
   (make-overlay 1 1)
   'display `(left-fringe right-arrow warning "left tooltip"))

;; 'before-string and 'after-string DO NOT work
  (overlay-put
   (make-overlay (point) (point))
   'before-string (propertize
                   "x" 'display
                   `(left-fringe right-arrow warning "left tooltip")))

Adding (when CONDITION . SPEC) support is easy, still figuring out
'before-string/'after-string.

Thanks

On Tue, 26 Mar 2024 at 22:16, Vladimir Kazanov <vekazanov@gmail.com> wrote:
>
> Hey,
>
> I just did a deep dive into the code again - looking for a cleaner solution.
>
> > The condition is only evaluated at glyph generation time, as for any
> > other display property.  When the tooltip should be displayed, the
> > condition is not relevant, since if it were false when the glyphs were
> > generated, you wouldn't have had the fringe bitmap shown in the first
> > place.
> >
> > However, I think there's an easy way of making the implementation
> > easier: just introduce a new overlay property called, say,
> > fringe-help-echo, and put that property on the same text as the
> > display property which produces the fringe.  Then the code in
> > note_fringe_highlight should simply check if the text which yielded
> > the fringe bitmap also has this special property on it, and if so,
> > display the tooltip.
>
> Maybe an even easier solution would work:
>
> 1. Record buffer position of the fringe display spec in struct it.
> Then move it to glyph_row the same way user_fringe_bitmap_id's are
> copied over.  It is just a ptrdiff so nothing out of place for
> glyph_rows.
>
> 2. In note_fringe_highlight it becomes easy to retrieve the fringe
> display spec using a single call to get_char_property_and_overlay(),
> no need to iterate over a line, or have the implementation detail leak
> into text properties.
>
> What I don't really understand is whether I should handle overlays
> with after-string/before-string properties. Overlays can contain
> strings propertized with fringe display specs as well. In fact, there
> is an example showing this trick in the manual
> (https://www.gnu.org/software/emacs/manual/html_node/elisp/Fringe-Bitmaps.html).
>
> Should I just go through all overlays touching the spec position and
> parse into the after-string/before-string as well?
>
> Pardon the many questions, display code has many moving parts.
>
> Thank you
>
> --
> Regards,
>
> Vladimir Kazanov



-- 
Regards,

Vladimir Kazanov