bug#38641: 27.0.50; Misbehavior when drawing a rectangular selection with the mouse

[Konrad Podczeck]

Using the mouse, start drawing a rectangular selection, with the upper
left corner _not_ in the first column. Extend the selection downwards
so that the left boundary of the selection continues to be in the same
column. As soon as one reaches the lower end of the frame, so that a
further extension of the selection produces scrolling of the text, the
position of the selection jumps so that its left boundary appears in the
first column.




In GNU Emacs 27.0.50 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1894.20 
Version 10.15.2 (Build 19C57))
 of 2019-12-16 built on Konrads-iMac.local
Windowing system distributor 'Apple', version 10.3.1894
System Description:  Mac OS X 10.15.2

Recent messages:
Loading cus-start...done
Loading tooltip...done
Loading /Applications/Emacs 2.app/Contents/Resources/lisp/leim/leim-list.el 
(source)...done
Finding pointers to doc strings...done
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading loadup.el (source)...done
<M-s-drag-mouse-1> is undefined [2 times]
Mark set (rectangle mode)
Mark set
Mark set (rectangle mode)

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 PDUMPER

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

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-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
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
format-spec rfc822 mml mml-sec epa derived epg epg-config gnus-util
rmail rmail-loaddefs text-property-search mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils time-date rect tex-site
info 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 cus-start 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:
((conses 16 288990 17606)
 (symbols 48 22286 1)
 (strings 32 62616 3662)
 (string-bytes 1 2578945)
 (vectors 16 54312)
 (vector-slots 8 1444549 37642)
 (floats 8 195 46)
 (intervals 56 219 0)
 (buffers 1000 13))