X11::Protocol::XSetRoot -- set root window background
X11::Protocol::XSetRoot->set_background (color => 'green');
# or given $X, but which then can't be used any more
(X => $X,
pixmap => $pixmap_xid,
pixmap_allocated_colors => 1);
This module sets the X root window background in the style of the
The simplest use is a named colour interpreted by the server's usual
"AllocNamedColor()" or a 1 to 4 digit hex string like
"#RRGGBB" or "#RRRRGGGGBBBB".
(color => 'green');
(color => '#FF0000'); # red
A pattern can be set with a pixmap. A pixmap the size of the screen can give a
full background picture.
# draw $pixmap with say $X->black_pixel and $X->white_pixel,
# then set it with
(X => $X,
pixmap => $pixmap);
"set_background()" takes ownership of the given $pixmap and frees it
with "FreePixmap()" once put into the window background.
Setting the root to a pixmap drawn by a program is the main use for this module.
If you just want a solid colour then that can be done easily enough with the
actual "xsetroot" program.
Allocated pixel colours (in "PseudoColor" etc) and any
"use_esetroot" preserve pixels and the pixmap with
"SetCloseDownMode ('RetainPermanent')" and leave root window
properties "_XSETROOT_ID" or "ESETROOT_PMAP_ID" ready to
released by a "KillClient()" in a future background change.
In these cases the $X connection cannot be used any more since a further
background change and consequent "KillClient()" could occur at any
time, perhaps immediately.
If a "pixmap" is given then if it contains any allocated pixels
("AllocColor()" etc) then this should be indicated with the
"pixmap_allocated_colors" option. (Allocated pixels are noticed
automatically for "pixel" and "color" options.)
# AllocColor colours, draw $pixmap with them, then
(X => $X,
pixmap => $pixmap,
pixmap_allocated_colors => 1);
# don't use $X any more
The easiest thing is to close an $X connection immediately after a
"set_background()". Perhaps there could be a return value to say
whether a retain was done and thus the connection cannot be used again. Or
perhaps in the future if "X11::Protocol" had an explicit
"$X->close()" then that could be done here so a closed connection
would indicate it cannot be used further.
If the root visual is static ("TrueColor" etc) then there's no colour
allocation as such ("AllocColor()" is just a lookup). In this case
"set_background()" knows there's no need for
"RetainPermanent" for colours, only for pixmaps.
If the "color" or "pixel" options are the screen
"black_pixel" or "white_pixel" then those pixels exist
permanently in the root colormap and "set_background()" knows
there's no need to "RetainPermanent" for them. If the server has the
TOG-CUP extension (see X11::Protocol::Ext::TOG_CUP) then any permanent pixels
there are recognised too.
"XSetRoot" looks for "__SWM_VROOT" using X11::Protocol::WM
"root_to_virtual_root()" and acts on that when applicable. Such a
virtual root is used by "amiwm", "swm" and
"tvtwm" window managers and the "xscreensaver" program.
The enlightenment window manager, however, uses a background window covering the
root window. This stops most root window programs from working, including
The "Esetroot" program and various compatible programs such as
"fvwm-root" use a separate set of properties from what
"xsetroot" uses. The "Esetroot" method records the root
pixmap ready for use by programs such as "Eterm", eg. to implement
pseudo-transparency (its "Eterm --trans", which the method was
The "set_background()" option "use_esetroot" uses the
"Esetroot" style rather than the default "xsetroot" style.
It can be used with the "pixel" or "color" options too and
in that case "set_background()" makes a 1x1 pixmap to give a solid
"set_background()" always deletes and kills (as appropriate) both the
"xsetroot" and "Esetroot" properties since both are
superseded by a new background.
For reference, to use "Eterm --trans" (as of its version 0.9.6 March
2011) an "Esetroot" background should be present when
"Eterm" starts and it should not be removed later (and not set to
"None"). "Eterm" won't notice an initial
"Esetroot" while it's running. This means do an "Esetroot"
before running "Eterm" and then do all future background changes in
The advantage of the "Esetroot" method is that the root pixmap is
available for client programs to use in creative ways. If the client draws
some of the root pixmap as its own background then it can appear
semi-transparent. This doesn't require the SHAPE extension and allows visual
effects like shading or dithering too.
For comparison, the "xsetroot" style means the root pixmap is not
available to client programs. In principle that allows the server to apply it
to the hardware and never refer to it again. In practice that might not occur,
for example if multiple console "virtual terminals" mean the server
must give up the hardware when switched away.
- "X11::Protocol::XSetRoot->set_background (key=>value,
- Set the root window background to a pixmap or colour. The key/value
X => X11::Protocol object
display => string ":0.0" etc
screen => integer, eg. 0
root => XID of root window
color => string
pixel => integer pixel value
pixmap => XID of pixmap to display, or "None"
pixmap_allocated_colors => boolean, default false
use_esetroot => boolean, default false
The server is given by an "X" connection object, or a
"display" name to connect to, or the default is the
"DISPLAY" environment variable.
The root window is given by "root" or "screen", or the
default is the default screen in $X either per
"$X->choose_screen()" or the default from the display name.
The background to show is given by a colour name, pixel value, or pixmap.
"color" can be anything understood by the server
"AllocNamedColor()", plus 1 to 4 digit hex
blue named colours
#RGB hex digits
"pixel" is an integer pixel value in the root window colormap.
It's automatically recognised as allocated or not (the screen pre-defined
black or white and TOG-CUP reserved pixels are permanent and so reckoned
"pixmap" is an XID integer. "set_background()" takes
ownership of this pixmap and will "FreePixmap()" once installed.
"None" or 0 means no pixmap, which gives the server's default
root background (usually a black and white weave pattern).
"pixmap_allocated_colors" should be true if any of the pixels in
"pixmap" were allocated with "AllocColor()" etc, as
opposed to just the screen pre-defined black and white pixels (and any
TOG-CUP permanent pixels).
"use_esetroot" means use the root window properties in the style
of "Esetroot". This allows programs such as "Eterm" to
use the root background for "pseudo-transparency" or in other
When an allocated pixel or a pixmap with allocated pixels is set as the
background the "_XSETROOT_ID" mechanism described above means
the $X connection could be killed by another "xsetroot" at any
time, perhaps immediately, and for that reason $X should not be used any
more. The easiest way is to make "set_background()" the last
thing done on $X.
Setting an allocated "pixel" or any "pixmap" can only be
done on a $X connection as such, not with the "display" option.
This is because retaining the colours with the "_XSETROOT_ID"
mechanism can only be done from the client connection which created the
resources, not a new separate client connection.
- For "xsetroot", if colours in the root window background are
allocated by "AllocColor()" etc then "_XSETROOT_ID" is
a pixmap XID which can be killed by "KillClient()" to free those
colours when the root background is replaced. "_XSETROOT_ID" is
only a 1x1 dummy pixmap, it's not the actual root background pixmap.
- For "Esetroot" style, this is the current root window background
pixmap. It might be set by an "Esetroot" which has run and
exited, or it might be set by a window manager or similar which is still
Client programs can use this to combine the root background into their own
window in interesting ways. Listen to "PropertyNotify" on the
root window for changes to "_XROOTPMAP_ID". Note that this
pixmap belongs to another client so it could be freed at any time.
Protocol errors when copying or drawing from it should generally be
ignored, or cause a fallback to some default.
- For "Esetroot" style, this is the same as
"_XROOTPMAP_ID" if that pixmap was created by
"Esetroot" and saved by
"SetCloseDownMode('RetainPermanent')". This should be freed by
"KillClient()" if the background is replaced.
The specification <http://www.eterm.org/docs/view.php?doc=ref#trans>
advises killing "ESETROOT_PMAP_ID" only when equal to
"_XROOTPMAP_ID". Probably it's safer to always kill
"ESETROOT_PMAP_ID" if replacing its value, to be sure of not
leaking resources. But perhaps if both "ESETROOT_PMAP_ID" and
"_XROOTPMAP_ID" exist then they are always equal.
- The default X server.
on the server, being the usual colour names database for
the "color" option above.
for a simple program to display the root window
Copyright 2010, 2011, 2012, 2013, 2014, 2017 Kevin Ryde
X11-Protocol-Other is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later version.
X11-Protocol-Other is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
You should have received a copy of the GNU General Public License along with
X11-Protocol-Other. If not, see <http://www.gnu.org/licenses/>.