Re: [PATCH] User-defined fringe tooltips (a request for review)

[Eli Zaretskii <eliz@gnu.org>]

> From: Vladimir Kazanov <vekazanov@gmail.com>
> Date: Sat, 23 Dec 2023 13:28:48 +0000
> Cc: emacs-devel@gnu.org
> 
> The way I see things now: the code has to iterate all charpos in the
> right order, including invisible ones, and also check for display
> properties in overlays. A glyph_row has information on where the row
> starts and ends (row->start and row->end).
> 
> I want to do the following in note_mouse_highlight:
> 
> /* Get to the current glyph row */
> struct glyph_row *row = MATRIX_ROW (w->current_matrix, vpos);
> Lisp_Object left_caption = Qnil, right_caption = Qnil;
> 
> ptrdiff_t charpos;
> ptrdiff_t charpos_start = row->start.pos.charpos;
> ptrdiff_t charpos_end = row->end.pos.charpos;
> for (charpos = charpos_start; charpos <= charpos_end; charpos++)
>   {
>     /* This can be either in text props or overlays, so check both */
>     Lisp_Object spec = get_char_property_and_overlay (make_fixnum (charpos),
> Qdisplay, Qnil, NULL);
>     /* ... parse the spec... */
>    }

Yes, I think you are right.  But I think it is better to use
row->minpos and row->maxpos; see the comments in dispextern.h for the
reasons why.

> > If Fget_text_property returns non-nil for the 'display' property, you
> > will then need to look at the value and see whether it specifies a
> > help-echo for the fringe; if it does, extract the string and assign it
> > to 'help_echo_string'.
> 
> I've just realized that what you have in mind is reusing the standard
> 'help-echo property? The one used for tooltips on the text itself?

No, that's not what I meant.  I only meant to assign the tip string to
help_echo_string like we do in other places in that function.

> Either way, I'd need to test this thoroughly, I suspect there might be
> interesting corner cases.

There always are, IME.

Thanks.