bug#12612: 24.2.50; Frame Background RGB(1,1,1) Darker Than Set Using GTK3

[Taylor Venable <tvenable@mieweb.com>]

When using GTK3, any time one sets the frame background (e.g. from
startup, or using set-frame-parameter) there is a difference between the
background color of the part of the frame with text, and the part of the
frame without. The part with text is correct, but the part of the frame
without is darker by 1 bit in all three RGB attributes. For example, the
default background is white; if you take a screenshot and look at the
result in the GIMP you will find that space between text is #ffffff,
whereas the background after the end of the line or buffer is #fefefe.

Only with GTK3 have I noticed this; with GTK2 this does not occur. It
happens with -Q. You don't notice it with light (Emacs) themes, but on
my monitor I can see it with darker (Emacs) themes fairly easily. When
in doubt, you can always check with a screenshot. The exception is if
the background is set to #000000, in which case everything has a
background of #000000 as it should.

I have no GTK3 theme set. Thanks for having a look.


In GNU Emacs 24.2.50.2 (x86_64-unknown-linux-gnu, GTK+ Version 3.4.4)
 of 2012-10-09 on trantor
Bzr revision: monnier@iro.umontreal.ca-20121009163751-ui2zwwoaj8bqwj52
Windowing system distributor `The X.Org Foundation', version 11.0.11204000
Configured using:
 `configure '--prefix=/usr' '--sysconfdir=/etc' '--localstatedir=/var'
 '--libexecdir=/usr/lib' '--mandir=/usr/share/man' '--without-sound'
 '--with-xft' '--with-x-toolkit=gtk3' 'CFLAGS=-march=x86-64
 -mtune=generic -O2 -pipe -fstack-protector --param=ssp-buffer-size=4
 -D_FORTIFY_SOURCE=2'
 'LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro''

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

Major mode: Lisp Interaction

Minor modes in effect:
  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
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<menu-bar> <help-menu> <send-emacs-bug-report>

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

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
easymenu 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 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)