X11::Protocol::GrabServer(3)
NAME
X11::Protocol::GrabServer -- object-oriented server grabbing
SYNOPSIS
use X11::Protocol::GrabServer;
{
my $grab = X11::Protocol::GrabServer->new ($X);
do_some_things();
# UngrabServer when $grab destroyed
}
DESCRIPTION
This is an object-oriented approach to GrabServer / UngrabServer on an
"X11::Protocol" connection. A grab object represents a desired server
grab and destroying it ungrabs.
The first grab object on a connection does a "GrabServer()" and the
last destroyed does an "UngrabServer()". The idea is that it's easier
to manage the lifespan of a grabbing object in a block etc than to be
sure of catching all exits.
Multiple grab objects can overlap or nest. A single "GrabServer()" is
done and it remains until the last object is destroyed. This is good
in a library or sub-function where an "UngrabServer()" should wait
until the end of outermost desired grab.
A server grab is usually to make a few operations atomic, for instance
something global like root window properties. A block-based temporary
object like the synopsis above is typical. It's also possible to hold
a grab object for an extended time, perhaps for some state driven
interaction with the server.
Care must be taken not to grab for too long since other client programs
are locked out. Also if a grabbing program hangs then the server will
be unusable until the program is killed, or its TCP etc server
connection is broken.
Weak $X
If Perl weak references are available (which means Perl 5.6 and up and
"Scalar::Util" with its usual XS code), then a grab object holds only a
weak reference to the target $X connection. This means the grab
doesn't keep the connection alive once nothing else is interested.
When a connection is destroyed the server ungrabs automatically and so
there's no need for an explicit "UngrabServer()" in that case.
The main effect of the weakening is that $X can be garbage collected
anywhere within a grabbing block, the same as if there was no grab.
Without the weakening it would wait until the end of the block. In
practice this only rarely makes a difference.
In the future if an "X11::Protocol" connection gets a notion of an
explicit close then the intention would be to skip any "UngrabServer()"
in that case too, ie. treat a closed connection the same as a weakened
away connection.
Currently no attention is paid to whether the server has disconnected
the link. A "UngrabServer()" is done on destroy in the usual way. If
the server has disconnected then a "SIGPIPE" or "EPIPE" occurs the same
as for any other request sent to the $X.
FUNCTIONS
"$g = X11::Protocol::GrabServer->new ($X)"
$X is an "X11::Protocol" object. Create and return a $g object
representing a grab of the $X server.
If this new $g is the first new grab on $X then an "$X->GrabServer"
is done.
"$g->ungrab ()"
Ungrab the $g object explicitly. An ungrab is done automatically
when $g is destroyed, but "$g->ungrab()" can do it sooner.
If $g is already ungrabbed then do nothing.
"$g->grab ()"
Re-grab with the $g object. This can be used after a
"$g->ungrab()" to grab again with the same object, the same as if
newly created.
If $g is already grabbing then do nothing.
"$bool = $g->is_grabbed ()"
Return true if $g is grabbing. This is true when first created, or
false after a "$g->ungrab()".
This function is only the state of $g. There might be other
"GrabServer" objects which grabbing the server.
SEE ALSO
X11::Protocol(3), X11::Protocol::Other(3)
HOME PAGE
<http://user42.tuxfamily.org/x11-protocol-other/index.html>
LICENSE
Copyright 2010, 2011, 2012, 2013, 2014 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 details.
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/>.
perl v5.28.1 2014-02-01 X11::Protocol::GrabServer(3)
x11-protocol-other 30 - Generated Mon Feb 18 18:25:16 CST 2019