Subject: bug#15837: closed (Re: bug#15837: [PATCH] Pass colours using rgb: instead of rgbi:)

From: [email-masked] (GNU bug Tracking System)
Date: Sat, 09 Nov 2013 11:22:02 +0000

Your bug report

#15837: 24.3; invalid colour conversion from Gtk+3 to X11

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
15837: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=15837
GNU Bug Tracking System
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Subject: Re: bug#15837: [PATCH] Pass colours using rgb: instead of rgbi:
From: Jan Djärv <[email-masked]>
To: Łukasz Stelmach <[email-masked]>
Cc: [email-masked]
Date: Sat, 9 Nov 2013 12:20:57 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

Applied, thanks.

	Jan D.

8 nov 2013 kl. 19:41 skrev Łukasz Stelmach <[email-masked]>:

> X procedures apply gamma correction to RGBi values which makes colours
> obtained from Gtk+ 3.0 and displayed by Emacs look different than in
> other Gtk applications.
> 
> Signed-off-by: Łukasz Stelmach <[email-masked]>
> ---
> src/gtkutil.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/src/gtkutil.c b/src/gtkutil.c
> index 7e304d4..b8d8610 100644
> --- a/src/gtkutil.c
> +++ b/src/gtkutil.c
> @@ -596,14 +596,17 @@ xg_check_special_colors (struct frame *f,
>     GtkStyleContext *gsty
>       = gtk_widget_get_style_context (FRAME_GTK_OUTER_WIDGET (f));
>     GdkRGBA col;
> -    char buf[sizeof "rgbi://" + 3 * (DBL_MAX_10_EXP + sizeof "-1.000000" - 1)];
> +    char buf[sizeof "rgb:rrrr/gggg/bbbb" ];
>     int state = GTK_STATE_FLAG_SELECTED|GTK_STATE_FLAG_FOCUSED;
>     if (get_fg)
>       gtk_style_context_get_color (gsty, state, &col);
>     else
>       gtk_style_context_get_background_color (gsty, state, &col);
> 
> -    sprintf (buf, "rgbi:%lf/%lf/%lf", col.red, col.green, col.blue);
> +    sprintf (buf, "rgb:%04x/%04x/%04x",
> +             (int)(col.red * 65535),
> +             (int)(col.green * 65535),
> +             (int)(col.blue * 65535));
>     success_p = (XParseColor (FRAME_X_DISPLAY (f), FRAME_X_COLORMAP (f),
> 			      buf, color)
> 		 != 0);
> -- 
> 1.8.1.5
> 
> 
> 

Subject: 24.3; invalid colour conversion from Gtk+3 to X11
From: Łukasz Stelmach <[email-masked]>
To: [email-masked]
Date: Fri, 08 Nov 2013 19:16:18 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

Hello,

The function[1] that reads foreground and background colours from Gtk+3
(GdkRGBA) and converts them to X11 ones (XColor) uses improper
intermediate representation. The Gtk coulour is formated as
rgbi:<red>/<green>/<blue>. Although values prefixed with rgbi: are meant
to be floating point values like the ones returned by
gtk_style_context_get_*() functions but unlike Gtk colours they are
meant to be linear intensity values and will be gamma corrected[2] using
the tables[3] in Xlib.

You can check the effect for yourself by running:

xterm -bg '#777'
xterm -bg 'rgb:7777/7777/7777'
xterm -bg 'rgb:0.46667/0.46667/0.46667'

The last one will be significantly lighter.

0.46667/0.46667/0.46667 is the value returned by Gtk when a colour is
set to #777.

A patch will follow this report.

References:

[1] http://git.savannah.gnu.org/cgit/emacs.git/tree/src/gtkutil.c?id=c09a36ec78af479cb2ea39bf4bca8743cecd08df#n601

[2] http://cgit.freedesktop.org/xorg/doc/xorg-docs/tree/man/X.man?id=66e800c69fa5348b01e4b9670d6274ba392db7e5#n562

[3] http://cgit.freedesktop.org/xorg/lib/libX11/tree/src/xcms/LRGB.c?id=6cb02b166361200da35ba14f52cd9aaa493eb0ea#n224
-- 
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>Łukasz<                                --- To dobrze, że mnie słuchasz.

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