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

[Eli Zaretskii <eliz@gnu.org>]

> From: Vladimir Kazanov <vekazanov@gmail.com>
> Date: Tue, 19 Dec 2023 19:38:09 +0000
> 
> Recently I've been looking into implementing a suggestion from
> etc/TODO related to fringe indicator tooltips:
> 
> > ** Allow fringe indicators to display a tooltip
> > Provide a help-echo property?
> 
> Attached is a quick and dirty proof-of-concept. The patch extends the
> display specification with an optional string that would be displayed
> through either tooltips or the echo area:
> 
> (overlay-put (make-overlay (point) (point))
>    'before-string (propertize "x" 'display `(left-fringe right-arrow
> nil "left fringe test tooltip")))
> 
> Moving a mouse pointer to the fringe would then display the string in
> a tooltip on a relevant line.

Thanks.

> To make this work I've extended "struct it" and "struct glyphs_row"
> with pointers to strings, and added some mouse hover handling in the
> "note_mouse_highlight function". Obviously, the code needs more checks
> but I want to confirm the approach with emacs-devel@ first.
> 
> Happy to hear comments and suggestions about the path taken!

I'm not sure I like to have Lisp_Object members in 'struct glyph_row'.
I also don't think I understand why you needed to copy the hel-echo
string to the glyph row.  The code in note_mouse_highlight examines
the buffer text and overlays for text properties whose meaning is to
display a help-echo string, so why cannot you do the same to look for
a 'display' property of this specific structure, and extract the
help-echo directly from there at mouse-highlight time instead of at
glyph-generation time?