bug#49622: 27.2; A new MacOS display heisenbug

[Devon Sean McCullough]

Glyph out of place, vertically shifted downwards:

Type ;; foo ⟡ bar
where a box ^ displays in place of the WHITE CONCAVE-SIDED DIAMOND
which can by typed by C-x 8 RET white concave-sided diamond RET
but renders as a box instead.

When I start Emacs, with or without init files,
the box is rendered in the correct screen position.

After editing for a while, the box renders on the line below.

                Peace
                        --Devon

P.S.  Please find screen shots at http://jovi.net/Emacs-Bug/Render

Any debugging suggestions?

I'm mailing this bug report from a fresh "CLEAN" emacs,
not the long-running bug-manifesting "DIRTY" emacs.

DIRTY Emacs has these additional features: (mode-local php-mode
conf-mode mule-diag filecache korea-util whitespace htmlfontify
htmlfontify-loaddefs lpr reposition gnutls url-http url-gw url-cache
url-auth warnings follow tramp-cache tramp-sh tramp tramp-loaddefs
trampver tramp-integration files-x tramp-compat edebug descr-text
hanja-util picture rng-xsd xsd-regexp rng-cmpct rng-nxml rng-valid
rng-loc rng-uri rng-parse nxml-parse rng-match rng-dt rng-util rng-pttrn
nxml-ns nxml-mode nxml-outln nxml-rap nxml-util nxml-enc xmltok novice
erc-truncate erc-speedbar erc-sound erc-services erc-replace erc-page
erc-notify erc-log erc-identd erc-ibuffer erc-ezbounce
erc-desktop-notifications notifications dbus erc-dcc erc-capab
erc-autoaway cus-edit ediff-ptch ediff-vers ediff ediff-merg ediff-mult
ediff-wind ediff-diff ediff-help ediff-init ediff-util woman sh-script
executable grep ibuf-ext ibuffer ibuffer-loaddefs goto-addr ffap
thai-util thai-word lao-util enriched macrostep-c cmacexp libgl-doc
face-remap cal-move play-sound smerge-mode diff completion pcase pulse
apropos vc-git erc-list erc-menu erc-join erc-ring erc-networks
erc-pcomplete erc-track erc-match erc-button erc-fill erc-stamp
erc-netsplit erc-goodies erc erc-backend erc-compat erc-loaddefs
mhtml-mode css-mode smie color js moz cc-mode cc-fonts cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs tabify eieio-opt
speedbar sb-image ezimage dframe man org-element avl-tree ol-eww eww
mm-url url-queue ol-rmail ol-mhe ol-irc ol-info ol-gnus nnir gnus-sum
url url-proxy url-privacy url-expand url-methods url-history mailcap shr
url-cookie url-domsuf url-util svg xml gnus-group gnus-undo gnus-start
gnus-cloud nnimap nnmail mail-source utf7 netrc nnoo gnus-spec gnus-int
gnus-range gnus-win gnus nnheader wid-edit ol-docview doc-view
image-mode exif ol-bibtex bibtex ol-bbdb ol-w3m org ob ob-tangle ob-ref
ob-lob ob-table ob-exp org-macro org-footnote org-src ob-comint
org-pcomplete org-list org-faces org-entities org-version ob-emacs-lisp
ob-core ob-eval org-table ol org-keys org-compat org-macs org-loaddefs
xr tar-mode pcmpl-unix pcmpl-gnu lisp-cycle view jka-compr gcl-info
network-stream nsm debug parse-time iso8601 help-fns radix-tree cl-print
server add-log dired-aux)

ERC does not immediately trigger this bug.

In GNU Emacs 27.2 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60 
Version 10.14.6 (Build 18G95))
 of 2021-03-27 built on builder10-14.porkrind.org
Windowing system distributor 'Apple', version 10.3.1671
System Description:  Mac OS X 10.14.6

Recent messages:
emacs   27.2    /Users/devon/.emacs
Appointment reminders enabled (no diary file found)
Idle timer set to 5 minutes
Loading gud...done
For information about GNU Emacs and the GNU system, type C-h C-a.
Package cl is deprecated
Mark set
user-error: No window right from selected window
Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp' --with-modules'

Configured features:
NOTIFY KQUEUE ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS MODULES
THREADS JSON PDUMPER GMP

Important settings:
  value of $LANG: en_BE@currency=USD.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
CLEAN                           DIRTY
                                erc-list-mode: t
                                erc-menu-mode: t
                                erc-autojoin-mode: t
                                erc-ring-mode: t
                                erc-networks-mode: t
                                erc-pcomplete-mode: t
                                erc-track-mode: t
                                erc-track-minor-mode: t
                                erc-match-mode: t
                                erc-button-mode: t
                                erc-fill-mode: t
                                erc-stamp-mode: t
                                erc-netsplit-mode: t
                                erc-irccontrols-mode: t
                                erc-noncommands-mode: t
                                erc-move-to-prompt-mode: t
                                erc-readonly-mode: t
  hi-lock-mode: t               hi-lock-mode: t
  gud-tooltip-mode: t           gud-tooltip-mode: t
  display-time-mode: t          display-time-mode: t
  which-function-mode: t        which-function-mode: t
  shell-dirtrack-mode: t        shell-dirtrack-mode: t
  tooltip-mode: t               tooltip-mode: t
  global-eldoc-mode: t          global-eldoc-mode: t
  eldoc-mode: t                 eldoc-mode: t
  electric-indent-mode: t       electric-indent-mode: t
  mouse-wheel-mode: t           mouse-wheel-mode: t
  menu-bar-mode: t              menu-bar-mode: t
  file-name-shadow-mode: t      file-name-shadow-mode: t
  global-font-lock-mode: t      global-font-lock-mode: t
  font-lock-mode: t             font-lock-mode: t
  blink-cursor-mode: t          blink-cursor-mode: t
  auto-composition-mode: t      auto-composition-mode: t
  auto-encryption-mode: t       auto-encryption-mode: t
  auto-compression-mode: t      auto-compression-mode: t
  temp-buffer-resize-mode: t    temp-buffer-resize-mode: t
  line-number-mode: t           line-number-mode: t
  transient-mark-mode: t        transient-mark-mode: t

Load-path shadows:
/Applications/Emacs.app/Contents/Resources/lisp/frame hides 
/Users/devon/emacs/frame
/Applications/Emacs.app/Contents/Resources/lisp/emacs-lisp/cl-macs hides 
/Users/devon/emacs/cl-macs
/Applications/Emacs.app/Contents/Resources/lisp/mail/sendmail hides 
/Users/devon/emacs/sendmail
/Applications/Emacs.app/Contents/Resources/lisp/play/morse hides 
/Users/devon/emacs/morse
/Applications/Emacs.app/Contents/Resources/lisp/indent hides 
/Users/devon/emacs/indent
/Applications/Emacs.app/Contents/Resources/lisp/forms hides 
/Users/devon/emacs/forms
/Applications/Emacs.app/Contents/Resources/lisp/mail/hashcash hides 
/Users/devon/emacs/hashcash
/Applications/Emacs.app/Contents/Resources/lisp/progmodes/inf-lisp hides 
/Users/devon/emacs/inf-lisp
~/emacs/swift-mode/swift-mode hides /Users/devon/emacs/swift-mode
/Applications/Emacs.app/Contents/Resources/lisp/dired-aux hides 
/Users/devon/emacs/dired-aux
/Applications/Emacs.app/Contents/Resources/lisp/json hides 
/Users/devon/emacs/json
/Applications/Emacs.app/Contents/Resources/lisp/net/shr hides 
/Users/devon/emacs/shr
/Applications/Emacs.app/Contents/Resources/lisp/replace hides 
/Users/devon/emacs/replace
/Applications/Emacs.app/Contents/Resources/lisp/textmodes/sgml-mode hides 
/Users/devon/emacs/sgml-mode
/Applications/Emacs.app/Contents/Resources/lisp/comint hides 
/Users/devon/emacs/comint
/Applications/Emacs.app/Contents/Resources/lisp/xml hides /Users/devon/emacs/xml
/Applications/Emacs.app/Contents/Resources/lisp/emacs-lisp/regexp-opt hides 
/Users/devon/emacs/regexp-opt
/Applications/Emacs.app/Contents/Resources/lisp/emacs-lisp/advice hides 
/Users/devon/emacs/advice
/Applications/Emacs.app/Contents/Resources/lisp/emacs-lisp/lisp hides 
/Users/devon/emacs/lisp
/Applications/Emacs.app/Contents/Resources/lisp/progmodes/xscheme hides 
/Users/devon/emacs/xscheme
/Users/devon/.emacs.d/elpa/csv-mode-1.7/csv-mode hides 
/Users/devon/emacs/csv-mode
/Applications/Emacs.app/Contents/Resources/lisp/textmodes/picture hides 
/Users/devon/emacs/picture
/Applications/Emacs.app/Contents/Resources/lisp/progmodes/xref hides 
/Users/devon/emacs/xref
/Applications/Emacs.app/Contents/Resources/lisp/rect hides 
/Users/devon/emacs/rect
/Applications/Emacs.app/Contents/Resources/lisp/lpr hides /Users/devon/emacs/lpr
/Applications/Emacs.app/Contents/Resources/lisp/net/tramp-ftp hides 
/Users/devon/emacs/tramp-ftp

Features:
(shadow mail-extr emacsbug message rmc puny format-spec rfc822 mml
mml-sec epa derived epg epg-config gnus-util rmail rmail-loaddefs
text-property-search time-date mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils hi-lock slime-pale slime-fancy
slime-indentation slime-cl-indent cl-indent slime-trace-dialog
slime-fontifying-fu slime-package-fu slime-references
slime-compiler-notes-tree slime-scratch slime-presentations bridge
slime-macrostep macrostep slime-mdot-fu slime-enclosing-context
slime-fuzzy slime-fancy-trace slime-fancy-inspector slime-c-p-c
slime-editing-commands slime-autodoc slime-repl slime-parse slime
compile arc-mode archive-mode noutline outline pp hyperspec thingatpt
hosts-config hosts windmove gud cus-start cus-load ls-lisp dired-x time
quote mouse-thing lzx iso-transl greek-keys which-func imenu new rect
shell pcomplete bucky cl-extra macosx sort etags fileloop generator xref
project compare-w diff-mode easy-mmode paren advice sgml-mode dom dired
dired-loaddefs info-look ispell disp-table edmacro kmacro supersub
comint ansi-color ring rx finder-inf backtrace help-mode find-func appt
diary-lib diary-loaddefs cal-menu calendar cal-loaddefs cl info
slime-autoloads package easymenu browse-url url-handlers url-parse
auth-source cl-seq eieio eieio-core cl-macs eieio-loaddefs
password-cache json subr-x map url-vars seq byte-opt gv bytecomp
byte-compile cconv cl-loaddefs cl-lib tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/ns-win ns-win
ucs-normalize mule-util term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode elisp-mode
lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch
timer select scroll-bar mouse jit-lock font-lock syntax facemenu
font-core term/tty-colors frame minibuffer 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 charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads kqueue cocoa ns
multi-tty make-network-process emacs)

Memory information:
CLEAN                           DIRTY
((conses 16 387725 13415)       ((conses 16 3554848 246049)
 (symbols 48 35966 5)            (symbols 48 61485 5)
 (strings 32 178224 2909)        (strings 32 319897 31643)
 (string-bytes 1 4222874)        (string-bytes 1 9301219)
 (vectors 16 33481)              (vectors 16 99794)
 (vector-slots 8 828529 20224)   (vector-slots 8 2295345 485158)
 (floats 8 185 59)               (floats 8 11613 576)
 (intervals 56 260 0)            (intervals 56 347213 7006)
 (buffers 1000 11))              (buffers 1000 210))