bug#23707: 25.0.94; Regression in mouse-set-region

[Alex]

When using the mouse to set a region outside of the current window, the
region is now created improperly. There are two basic cases:

a) dragging the mouse and ending on or outside the Emacs frame causes no
region to be created

Steps to reproduce:

1. emacs -Q
2. In the scratch buffer with <mouse-1>, drag the region and end off in
the menu-bar area.
3. The region is not created.

b) dragging the mouse and ending in another Emacs window causes a region
to be created between the starting point and the point corresponding to
the ending point *in the other buffer*.

1. emacs -Q
2. C-x 2
3. C-x 0
4. In the bottom scratch window, drag with your mouse and end somewhere
in the scratch message int he top window
5. The region is created, but ends prematurely at whatever point you
ended at in the top window.


Emacs 24.5 had the correct behaviour of creating a region between the
starting point and one of the ends of the buffer when dragging outside
of the current window.

In GNU Emacs 25.0.94.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.18.9)
 of 2016-05-17 built on lylat
Windowing system distributor 'Fedora Project', version 11.0.11803000
Configured using:
 'configure --with-gif=no'

Configured features:
XPM JPEG TIFF PNG SOUND DBUS GSETTINGS NOTIFY FREETYPE XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
  value of $LC_CTYPE: en_CA.utf8
  value of $LANG: en_CA.utf8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

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 dired format-spec rfc822 mml
mml-sec password-cache epg 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 cl-extra
help-fns help-mode easymenu cl-loaddefs pcase cl-lib time-date mule-util
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel x-win term/common-win x-dnd tool-bar dnd fontset image regexp-opt
fringe tabulated-list newcomment elisp-mode lisp-mode prog-mode register
page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core 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 charscript case-table epa-hook
jka-cmpr-hook help simple abbrev 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 dbusbind inotify dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 88650 8250)
 (symbols 48 19654 1)
 (miscs 40 73 288)
 (strings 32 14307 4665)
 (string-bytes 1 411990)
 (vectors 16 11811)
 (vector-slots 8 429433 6340)
 (floats 8 168 88)
 (intervals 56 243 0)
 (buffers 976 12)
 (heap 1024 46192 1533))