bug#14598: 24.3; global-hl-line-mode + text-scale-adjust + next-line + scrolling

[Phil Sainty]

With global-hl-line-mode enabled (but not local hl-line-mode,
which is implemented differently) and with a smaller font via
text-scale-adjust, scrolling off the bottom of the window with
next-line gets incredibly glitchy.

Recipe:

* emacs -Q
* Visit a file or add text with more lines than the current window
* M-x global-hl-line-mode
* C-x C--
* Hold down C-n




In GNU Emacs 24.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.4.2)
 of 2013-04-14 on chindi10, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.11300000
System Description:     Ubuntu 12.04.2 LTS

Configured using:
 `configure '--build' 'x86_64-linux-gnu' '--build' 'x86_64-linux-gnu'
 '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
 '--localstatedir=/var/lib' '--infodir=/usr/share/info'
 '--mandir=/usr/share/man' '--with-pop=yes'

'--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.3/site-lisp:/usr/share/emacs/site-lisp'
 '--with-crt-dir=/usr/lib/x86_64-linux-gnu' '--with-x=yes'
 '--with-x-toolkit=gtk3' '--with-toolkit-scroll-bars'
 'build_alias=x86_64-linux-gnu' 'CFLAGS=-g -O2 -fstack-protector
 --param=ssp-buffer-size=4 -Wformat -Wformat-security
 -Werror=format-security -Wall' 'LDFLAGS=-Wl,-Bsymbolic-functions
 -Wl,-z,relro' 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LANG: en_NZ.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Emacs-Lisp

Minor modes in effect:
  text-scale-mode: t
  global-hl-line-mode: t
  tooltip-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
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n <down> <down> M-x r e p o r t <tab> <r
eturn>

Recent messages:
Auto-saving...
<down> runs the command next-line
uncompressing simple.el.gz...done
Note: file is write protected
Mark set
Mark saved where search started
Type C-x 1 to delete the help window.
<down> runs the command next-line
Auto-saving...
Use +,-,0 for further adjustment

Load-path shadows:
None found.

Features:
(help-fns misearch multi-isearch jka-compr find-func shadow sort
gnus-util mail-extr emacsbug message format-spec rfc822 mml mml-sec
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr
mail-utils face-remap cus-start cus-load hl-line js byte-opt bytecomp
byte-compile cconv json imenu thingatpt cc-mode cc-fonts cc-guess
cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs sh-script
smie executable dired help-mode easymenu time-date tooltip ediff-hook
vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode register page
menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core frame cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote make-network-process dbusbind dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty emacs)