bug#64101: 29.0.91; Eglot inlay hints rendered out of order

[João Távora]

Eli Zaretskii <eliz@gnu.org> writes:

> João, are you looking into this?  

I looked at a very similar issue: 
https://github.com/joaotavora/eglot/discussions/1239

There, Milan Jovanovic , reports something very similar,
if not completely identical, for Emacs 29.  I asked
Milan to send mail here.  Maybe Krzystof and Milan are
related, or this is just a coincidence?

Anyway, I tried to reproduce the problem on both Emacs 29
and 30 and couldn't.

The problem also doesn't happen on Emacs 28.  So I don't know what is up
and the "recent overlay rewrite" (when?) doesn't seem to have an effect.
I don't have a Mac OS machine to test.

> Should the overlays created for the
> inlay hints be forced to be sorted in some particular order?

Maybe, and there is definitely an order they should be sorted.
But as far as I can personally observe, there is no problem yet,
so it would be best to first understand the problem.

But maybe Milan/Krzystof can try this patch:

diff --git a/lisp/progmodes/eglot.el b/lisp/progmodes/eglot.el
index a65795f1dfc..0c000f72ec7 100644
--- a/lisp/progmodes/eglot.el
+++ b/lisp/progmodes/eglot.el
@@ -3755,8 +3755,9 @@ eglot--update-hints-1
                      (if peg-after-p
                          (make-overlay (point) (1+ (point)) nil t)
                        (make-overlay (1- (point)) (point) nil nil nil)))
-                   (do-it (label lpad rpad firstp)
-                     (let* ((tweak-cursor-p (and firstp peg-after-p))
+                   (do-it (label lpad rpad i)
+                     (let* ((firstp (zerop i))
+                            (tweak-cursor-p (and firstp peg-after-p))
                             (ov (make-ov))
                             (text (concat lpad label rpad)))
                        (when tweak-cursor-p (put-text-property 0 1 'cursor 1 
text))
@@ -3767,17 +3768,18 @@ eglot--update-hints-1
                                              (1 'eglot-type-hint-face)
                                              (2 'eglot-parameter-hint-face)
                                              (_ 'eglot-inlay-hint-face))))
+                       (overlay-put ov 'priority i)
                        (overlay-put ov 'eglot--inlay-hint t)
                        (overlay-put ov 'evaporate t)
                        (overlay-put ov 'eglot--overlay t))))
-                (if (stringp label) (do-it label left-pad right-pad t)
+                (if (stringp label) (do-it label left-pad right-pad 0)
                   (cl-loop
                    for i from 0 for ldetail across label
                    do (eglot--dbind ((InlayHintLabelPart) value) ldetail
                         (do-it value
                                (and (zerop i) left-pad)
                                (and (= i (1- (length label))) right-pad)
-                               (zerop i))))))))))
+                               i)))))))))
     (jsonrpc-async-request
      (eglot--current-server-or-lose)
      :textDocument/inlayHint