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.IX Title "Glib::MainLoop 3"
.TH Glib::MainLoop 3 2025-07-13 "perl v5.42.0" "User Contributed Perl Documentation"
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.nh
.SH NAME
Glib::MainLoop \-  An event source manager
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Event\-driven programs need some sort of loop which watches for events and
launches the appropriate actions.  Glib::MainLoop provides this functionality.
.PP
Mainloops have context, provided by the MainContext object.  For the most part
you can use the default context (see \f(CW\*(C`default\*(C'\fR), but if you want to create a
subcontext for a nested loop which doesn\*(Aqt have the same event sources, etc,
you can.
.PP
Event sources, attached to main contexts, watch for events to happen, and
launch appropriate actions.  Glib provides a few ready\-made event sources,
the Glib::Timeout, Glib::Idle, and io watch (\f(CW\*(C`Glib::IO\->add_watch\*(C'\fR).
.PP
Under the hood, Gtk+ adds event sources for GdkEvents to dispatch events to
your widgets.  In fact, Gtk2 provides an abstraction of Glib::MainLoop (See
\&\f(CW\*(C`Gtk2\->main\*(C'\fR and friends), so you may rarely have cause to use
Glib::MainLoop directly.
.PP
Note: As of version 1.080, the Glib module uses a custom event source to
ensure that perl\*(Aqs safe signal handling and the glib polling event loop
play nicely together.  It is no longer necessary to install a timeout to
ensure that async signals get handled in a timely manner.
.SH CONSTANTS
.IX Header "CONSTANTS"
\&\f(CW\*(C`SOURCE_REMOVE\*(C'\fR and \f(CW\*(C`SOURCE_CONTINUE\*(C'\fR are designed for use as the
return values from timeout, idle and I/O watch source functions.  They
return true to keep running or false to remove themselves.  These
constants can help you get that the right way around.
.PP
.Vb 2
\&    Glib::SOURCE_CONTINUE     # true
\&    Glib::SOURCE_REMOVE       # false
.Ve
.SH METHODS
.IX Header "METHODS"
.SS "maincontext thingamabob = Glib::MainContext\->\fBnew\fP"
.IX Subsection "maincontext thingamabob = Glib::MainContext->new"
.ie n .SS "mainloop = Glib::MainLoop\->\fBnew\fP ($context=undef, $is_running=FALSE)"
.el .SS "mainloop = Glib::MainLoop\->\fBnew\fP ($context=undef, \f(CW$is_running\fP=FALSE)"
.IX Subsection "mainloop = Glib::MainLoop->new ($context=undef, $is_running=FALSE)"
.IP \(bu 4
\&\f(CW$context\fR (Glib::MainContext thingamabob)
.IP \(bu 4
\&\f(CW$is_running\fR (boolean)
.ie n .SS "integer = Glib::Timeout\->\fBadd\fP ($interval, $callback, $data=undef, $priority=G_PRIORITY_DEFAULT)"
.el .SS "integer = Glib::Timeout\->\fBadd\fP ($interval, \f(CW$callback\fP, \f(CW$data\fP=undef, \f(CW$priority\fP=G_PRIORITY_DEFAULT)"
.IX Subsection "integer = Glib::Timeout->add ($interval, $callback, $data=undef, $priority=G_PRIORITY_DEFAULT)"
.IP \(bu 4
\&\f(CW$interval\fR (integer) number of milliseconds
.IP \(bu 4
\&\f(CW$callback\fR (subroutine)
.IP \(bu 4
\&\f(CW$data\fR (scalar)
.IP \(bu 4
\&\f(CW$priority\fR (integer)
.PP
Run \fR\f(CI$callback\fR\fI\fR every \fI\fR\f(CI$interval\fR\fI\fR milliseconds until \fI\fR\f(CI$callback\fR\fI\fR returns
false.  Returns a source id which may be used with \f(CW\*(C`Glib::Source\->remove\*(C'\fR.
Note that a mainloop must be active for the timeout to execute.
.ie n .SS "integer = Glib::Idle\->\fBadd\fP ($callback, $data=undef, $priority=G_PRIORITY_DEFAULT_IDLE)"
.el .SS "integer = Glib::Idle\->\fBadd\fP ($callback, \f(CW$data\fP=undef, \f(CW$priority\fP=G_PRIORITY_DEFAULT_IDLE)"
.IX Subsection "integer = Glib::Idle->add ($callback, $data=undef, $priority=G_PRIORITY_DEFAULT_IDLE)"
.IP \(bu 4
\&\f(CW$callback\fR (subroutine)
.IP \(bu 4
\&\f(CW$data\fR (scalar)
.IP \(bu 4
\&\f(CW$priority\fR (integer)
.PP
Run \fR\f(CI$callback\fR\fI\fR when the mainloop is idle.  If \fI\fR\f(CI$callback\fR\fI\fR returns false,
it will uninstall itself, otherwise, it will run again at the next idle
iteration.  Returns a source id which may be used with
\&\f(CW\*(C`Glib::Source\->remove\*(C'\fR.
.ie n .SS "integer = Glib::Timeout\->\fBadd_seconds\fP ($interval, $callback, $data=undef, $priority=G_PRIORITY_DEFAULT)"
.el .SS "integer = Glib::Timeout\->\fBadd_seconds\fP ($interval, \f(CW$callback\fP, \f(CW$data\fP=undef, \f(CW$priority\fP=G_PRIORITY_DEFAULT)"
.IX Subsection "integer = Glib::Timeout->add_seconds ($interval, $callback, $data=undef, $priority=G_PRIORITY_DEFAULT)"
.IP \(bu 4
\&\f(CW$interval\fR (integer)
.IP \(bu 4
\&\f(CW$callback\fR (scalar)
.IP \(bu 4
\&\f(CW$data\fR (scalar)
.IP \(bu 4
\&\f(CW$priority\fR (integer)
.PP
Since: glib 2.14
.ie n .SS "integer = Glib::IO\->\fBadd_watch\fP ($fd, $condition, $callback, $data=undef, $priority=G_PRIORITY_DEFAULT)"
.el .SS "integer = Glib::IO\->\fBadd_watch\fP ($fd, \f(CW$condition\fP, \f(CW$callback\fP, \f(CW$data\fP=undef, \f(CW$priority\fP=G_PRIORITY_DEFAULT)"
.IX Subsection "integer = Glib::IO->add_watch ($fd, $condition, $callback, $data=undef, $priority=G_PRIORITY_DEFAULT)"
.IP \(bu 4
\&\f(CW$fd\fR (integer) file descriptor, e.g. fileno($filehandle)
.IP \(bu 4
\&\f(CW$condition\fR (Glib::IOCondition)
.IP \(bu 4
\&\f(CW$callback\fR (subroutine)
.IP \(bu 4
\&\f(CW$data\fR (scalar)
.IP \(bu 4
\&\f(CW$priority\fR (integer)
.PP
Run \fR\f(CI$callback\fR\fI\fR when there is an event on \fI\fR\f(CI$fd\fR\fI\fR that matches \fI\fR\f(CI$condition\fR\fI\fR.
The watch uninstalls itself if \fI\fR\f(CI$callback\fR\fI\fR returns false.
Returns a source id that may be used with \f(CW\*(C`Glib::Source\->remove\*(C'\fR.
.PP
Glib\*(Aqs IO channels serve the same basic purpose as Perl\*(Aqs file handles, so
for the most part you don\*(Aqt see GIOChannels in Perl.  The IO watch integrates
IO operations with the main loop, which Perl file handles don\*(Aqt do.  For
various reasons, this function requires raw file descriptors, not full
file handles.  See \f(CW\*(C`fileno\*(C'\fR in perlfunc.
.ie n .SS "maincontext thingamabob = $loop\->\fBget_context\fP"
.el .SS "maincontext thingamabob = \f(CW$loop\fP\->\fBget_context\fP"
.IX Subsection "maincontext thingamabob = $loop->get_context"
.SS "maincontext thingamabob = Glib::MainContext\->\fBdefault\fP"
.IX Subsection "maincontext thingamabob = Glib::MainContext->default"
.ie n .SS "boolean = $context\->\fBis_owner\fP"
.el .SS "boolean = \f(CW$context\fP\->\fBis_owner\fP"
.IX Subsection "boolean = $context->is_owner"
Since: glib 2.12
.ie n .SS "boolean = $loop\->\fBis_running\fP"
.el .SS "boolean = \f(CW$loop\fP\->\fBis_running\fP"
.IX Subsection "boolean = $loop->is_running"
.ie n .SS "boolean = $context\->\fBiteration\fP ($may_block)"
.el .SS "boolean = \f(CW$context\fP\->\fBiteration\fP ($may_block)"
.IX Subsection "boolean = $context->iteration ($may_block)"
.IP \(bu 4
\&\f(CW$may_block\fR (boolean)
.SS "integer = Glib::main_depth"
.IX Subsection "integer = Glib::main_depth"
Find the current main loop recursion level.  This is handy in fringe
situations, but those are very rare; see the C API reference for a more
in\-depth discussion.
.PP
Since: glib 2.4
.ie n .SS "boolean = $context\->\fBpending\fP"
.el .SS "boolean = \f(CW$context\fP\->\fBpending\fP"
.IX Subsection "boolean = $context->pending"
.ie n .SS $loop\->\fBquit\fP
.el .SS \f(CW$loop\fP\->\fBquit\fP
.IX Subsection "$loop->quit"
.SS "boolean = Glib::Source\->\fBremove\fP ($tag)"
.IX Subsection "boolean = Glib::Source->remove ($tag)"
.IP \(bu 4
\&\f(CW$tag\fR (integer)
.PP
Remove an event source.  \fR\f(CI$tag\fR\fI\fR is the number returned by things like
\&\f(CW\*(C`Glib::Timeout\->add\*(C'\fR, \f(CW\*(C`Glib::Idle\->add\*(C'\fR, and
\&\f(CW\*(C`Glib::IO\->add_watch\*(C'\fR.
.ie n .SS $loop\->\fBrun\fP
.el .SS \f(CW$loop\fP\->\fBrun\fP
.IX Subsection "$loop->run"
.ie n .SS "integer = Glib::Child\->\fBwatch_add\fP ($pid, $callback, $data=undef, $priority=G_PRIORITY_DEFAULT)"
.el .SS "integer = Glib::Child\->\fBwatch_add\fP ($pid, \f(CW$callback\fP, \f(CW$data\fP=undef, \f(CW$priority\fP=G_PRIORITY_DEFAULT)"
.IX Subsection "integer = Glib::Child->watch_add ($pid, $callback, $data=undef, $priority=G_PRIORITY_DEFAULT)"
.IP \(bu 4
\&\f(CW$pid\fR (integer) child process ID
.IP \(bu 4
\&\f(CW$callback\fR (subroutine)
.IP \(bu 4
\&\f(CW$data\fR (scalar)
.IP \(bu 4
\&\f(CW$priority\fR (integer)
.PP
Add a source to the default main context which will call
.PP
.Vb 1
\&    &$callback ($pid, $waitstatus, $data)
.Ve
.PP
when child process \f(CW$pid\fR terminates.  The return value is a source id
which can be used with \f(CW\*(C`Glib::Source\->remove\*(C'\fR.  When the callback
is made the source is removed automatically.
.PP
In a non\-threaded program Glib implements this source by installing a
SIGCHLD handler.  Don\*(Aqt change \f(CW$SIG\fR{CHLD} in Perl or the callback will
never run.
.PP
Since: glib 2.4
.SH "ENUMS AND FLAGS"
.IX Header "ENUMS AND FLAGS"
.SS "flags Glib::IOCondition"
.IX Subsection "flags Glib::IOCondition"
.IP \(bu 4
\&\*(Aqin\*(Aq / \*(AqG_IO_IN\*(Aq
.IP \(bu 4
\&\*(Aqout\*(Aq / \*(AqG_IO_OUT\*(Aq
.IP \(bu 4
\&\*(Aqpri\*(Aq / \*(AqG_IO_PRI\*(Aq
.IP \(bu 4
\&\*(Aqerr\*(Aq / \*(AqG_IO_ERR\*(Aq
.IP \(bu 4
\&\*(Aqhup\*(Aq / \*(AqG_IO_HUP\*(Aq
.IP \(bu 4
\&\*(Aqnval\*(Aq / \*(AqG_IO_NVAL\*(Aq
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Glib
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright (C) 2003\-2011 by the gtk2\-perl team.
.PP
This software is licensed under the LGPL.  See Glib for a full notice.