bug#55203: 29.0.50; MSW menu bar help text doesn't show when blink-cursor-mode is off

bug#55203: 29.0.50; MSW menu bar help text doesn't show when blink-cursor-mode is off

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Move the mouse over any menu bar item that normally shows a tooltip.
That tooltip will not be displayed if `blink-cursor-mode' is turned off.

In GNU Emacs 29.0.50 (build 2, x86_64-w64-mingw32)
 of 2022-05-01 built on DESKTOP-Q5AN53D
Repository revision: 07ae30d8f24ce46dbb7c2fbfa02002c1b4c2b6b7
Repository branch: master
Windowing system distributor 'Microsoft Corp.', version 10.0.19044
System Description: Microsoft Windows 10 Pro (v10.0.2009.19044.1645)

Configured using:
 'configure
 PKG_CONFIG_PATH=/mingw64/lib/pkgconfig:/mingw64/share/pkgconfig'

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NOTIFY
W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS WEBP XPM ZLIB

Important settings:
  value of $LC_CTYPE: en_US.UTF-8
  value of $LANG: ENU
  locale-coding-system: cp1252

Major mode: Compilation

Minor modes in effect:
  shell-dirtrack-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  buffer-read-only: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media rmc puny
dired dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg
rfc6068 epg-config gnus-util mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils smerge-mode diff whitespace
time-date shell pcomplete compile text-property-search comint ansi-color
ring misearch multi-isearch vc-git diff-mode easy-mmode vc vc-dispatcher
bug-reference cc-mode cc-fonts cc-guess cc-menus cc-cmds cc-styles
cc-align cc-engine cc-vars cc-defs cl-loaddefs cl-lib seq gv subr-x
byte-opt bytecomp byte-compile cconv cus-start cus-load iso-transl
tooltip eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel dos-w32 ls-lisp disp-table
term/w32-win w32-win w32-vars term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer nadvice simple cl-generic cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese composite emoji-zwj charscript charprop
case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
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text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget keymap hashtable-print-readable backquote threads
w32notify w32 lcms2 multi-tty make-network-process emacs)

Memory information:
((conses 16 107872 10981)
 (symbols 48 10192 1)
 (strings 32 30446 1639)
 (string-bytes 1 1360688)
 (vectors 16 17313)
 (vector-slots 8 227274 14462)
 (floats 8 34 321)
 (intervals 56 4195 0)
 (buffers 992 19))

bug#55203: 29.0.50; MSW menu bar help text doesn't show when blink-cursor-mode is off

[Eli Zaretskii]

> Date: Sun, 01 May 2022 11:00:11 +0800
> From:  Po Lu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> 
> Move the mouse over any menu bar item that normally shows a tooltip.
> That tooltip will not be displayed if `blink-cursor-mode' is turned off.

This is a well-known problem.  It is caused by the implementation of
Emacs menus on MS-Windows: we start a separate message loop for
handling the menu events, and this suspends the main event loop.  When
blink-cursor-mode is ON, the timer causes the main event loop to turn
a notch, and then Emacs produces the help-echo for the menu item; but
without cursor blinking and no other sources of async input events,
that doesn't happen.

Patches to fix that are welcome.

bug#55203: 29.0.50; MSW menu bar help text doesn't show when blink-cursor-mode is off

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Eli Zaretskii <eliz@gnu.org> writes:

> This is a well-known problem.  It is caused by the implementation of
> Emacs menus on MS-Windows: we start a separate message loop for
> handling the menu events, and this suspends the main event loop.  When
> blink-cursor-mode is ON, the timer causes the main event loop to turn
> a notch, and then Emacs produces the help-echo for the menu item; but
> without cursor blinking and no other sources of async input events,
> that doesn't happen.

Thanks.  Could you point to where that "separate message loop" is
started?  I couldn't find anything in w32menu.c.

bug#55203: 29.0.50; MSW menu bar help text doesn't show when blink-cursor-mode is off

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: 55203@debbugs.gnu.org
> Date: Sun, 01 May 2022 14:32:14 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > This is a well-known problem.  It is caused by the implementation of
> > Emacs menus on MS-Windows: we start a separate message loop for
> > handling the menu events, and this suspends the main event loop.  When
> > blink-cursor-mode is ON, the timer causes the main event loop to turn
> > a notch, and then Emacs produces the help-echo for the menu item; but
> > without cursor blinking and no other sources of async input events,
> > that doesn't happen.
> 
> Thanks.  Could you point to where that "separate message loop" is
> started?  I couldn't find anything in w32menu.c.

It's in w32fns.c, under WM_EMACS_TRACKPOPUPMENU.  w32menu.c sends the
WM_EMACS_TRACKPOPUPMENU message to the main window procedure when the
menu is ready to be displayed.  We then call TrackPopupMenu and
discard any mouse events except those which select a menu item (AFAIU
what happens there; I'm nowhere close to being an expert on this
stuff).