Hi all,

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.

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!

Thank you

-- 
Regards,

Vladimir Kazanov