I've been experimenting around to make Emacs scroll with pixel-level
precision and have soon discovered `set-window-vscroll' which allows one
to adjust the vertical scrolling of a window in pixel steps with its
fourth argument.  In an attempt to scroll further than a screenful, I
executed (set-window-vscroll nil 9000 t) which hung up Emacs.  Bisection
of my init file revealed that this issue doesn't happen with an
uncustomized Emacs and that it's sufficient to either customize
`scroll-step' to have a value of 1 or `scroll-conservatively' to have a
large value (which is a common hack to allow line-level scrolling).  Is
this interaction a bug?  If not, can it at the very least be documented
in the docstring of `set-window-vscroll'?



In GNU Emacs 24.4.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.14.3)
 of 2014-10-21 on bitzer.hoetzel.info
Windowing system distributor `The X.Org Foundation', version 11.0.11603000
System Description: Arch Linux

Configured using:
 `configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --with-x-toolkit=gtk3 --with-xft
 'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong
 --param=ssp-buffer-size=4' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro'

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

Major mode: Fundamental

Minor modes in effect:
  tooltip-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
  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:
M-x r e p o <tab> <down-mouse-2> <mouse-2>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list...

Load-path shadows:
/usr/share/emacs/site-lisp/SuperCollider/tree-widget hides
/usr/share/emacs/24.4/lisp/tree-widget

Features:
(shadow sort gnus-util mail-extr emacsbug message idna 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 help-fns mail-prsvr mail-utils help-mode easymenu time-date
tooltip electric uniquify 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 prog-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 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 make-network-process
dbusbind gfilenotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 74922 7762)
 (symbols 48 17669 0)
 (miscs 40 80 138)
 (strings 32 9343 4421)
 (string-bytes 1 257939)
 (vectors 16 9064)
 (vector-slots 8 385359 16597)
 (floats 8 65 302)
 (intervals 56 227 4)
 (buffers 960 13)
 (heap 1024 41177 904))