bug#30929: 26.0.91; Text drag and drop does not work

[Nick Helm <nick@tenpoint.co.nz>]

On MacOS text drag-n-drop does not work out of the box. Also a dnd 
event seems to be bound to different functions depending on modifier 
settings.

Emacs -Q

C-h v ns-command-modifier -> "It's value is super"

C-h k <drag and drop external text> 
  -> "<M-s-drag-n-drop> is undefined"

(setq ns-command-modifier 'none)
C-h k <drag and drop external text>
  -> "<M-drag-n-drop> at that spot runs the command
      ns-drag-n-drop-as-text"

(setq ns-command-modifier 'control)
C-h k <drag and drop external text>
  -> "<C-M-drag-n-drop> at that spot runs the command
      ns-drag-n-drop-as-text-other-frame"

etc


In GNU Emacs 26.0.91 (build 1, x86_64-apple-darwin17.4.0, NS appkit-1561.20 Version 10.13.3 (Build 17D102))
 of 2018-03-22 built on jupiter.local
Repository revision: f8cad16bb3272a8069b3008019f9d18516aef1a5
Windowing system distributor 'Apple', version 10.3.1561
Recent messages:
Opening nnimap server on Office365...
Opening connection to localhost via shell...
Opening connection to localhost...done
Opening nnimap server on Office365...done
Opening nntp server on Gmane...done
1 new newsgroup has arrived
Checking new news...
Reading active file via nnnil...done
Reading active file via nndraft...done
Checking new news...done

Configured using:
 'configure --with-gnutls=no'

Configured features:
JPEG NOTIFY ACL LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS THREADS LCMS2

Important settings:
  value of $LANG: en_NZ.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Text

Minor modes in effect:
  savehist-mode: t
  global-eldoc-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  visual-line-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow gnus-cite sort mail-extr nnir emacsbug sendmail gnus-demon
nndraft nnmh cl-extra help-mode utf-7 network-stream nsm auth-source
cl-seq eieio eieio-core cl-macs eieio-loaddefs starttls nnfolder nnnil
gnus-agent gnus-srvr gnus-score score-mode nnvirtual gnus-msg gnus-art
mm-uu mml2015 mm-view mml-smime smime dig mailcap nntp gnus-cache
gnus-sum gnus-group gnus-undo gnus-start gnus-cloud nnimap nnmail
mail-source tls gnutls utf7 netrc nnoo parse-time gnus-spec gnus-int
gnus-range message rmc puny seq byte-opt bytecomp byte-compile cconv
format-spec rfc822 mml mml-sec password-cache epa derived epg epg-config
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader gnus-win gnus nnheader gnus-util rmail rmail-loaddefs rfc2047
rfc2045 ietf-drums mail-utils mm-util mail-prsvr wid-edit time dired-x
easymenu dired dired-loaddefs pcase savehist easy-mmode iso-transl
edmacro kmacro cl-loaddefs cl-lib gv plain-theme time-date 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 menu-bar rfn-eshadow
isearch timer select scroll-bar mouse jit-lock font-lock syntax facemenu
font-core term/tty-colors frame 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 minibuffer 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 kqueue cocoa ns lcms2 multi-tty
make-network-process emacs)

Memory information:
((conses 16 282192 18056)
 (symbols 48 28457 1)
 (miscs 40 54 283)
 (strings 32 54201 2932)
 (string-bytes 1 1603692)
 (vectors 16 43788)
 (vector-slots 8 823234 17468)
 (floats 8 217 385)
 (intervals 56 246 0)
 (buffers 992 16))