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<?xml version="1.0" standalone="no"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
<refentry id="class-giocancellable">
<refnamediv>
<refname>gio.Cancellable</refname>
<refpurpose>Thread-safe Operation Cancellation Stack.</refpurpose>
</refnamediv>
<refsect1>
<title>Synopsis</title>
<classsynopsis language="python">
<ooclass><classname>gio.Cancellable</classname></ooclass>
<ooclass><classname><link linkend="class-gobject">gobject.GObject</link></classname></ooclass>
<constructorsynopsis language="python">
<methodname><link linkend="constructor-giocancellable">gio.Cancellable</link></methodname>
<methodparam></methodparam>
</constructorsynopsis>
<methodsynopsis language="python">
<methodname><link linkend="method-giocancellable--cancel">cancel</link></methodname>
<methodparam></methodparam>
</methodsynopsis>
<methodsynopsis language="python">
<methodname><link linkend="method-giocancellable--get-fd">get_fd</link></methodname>
<methodparam></methodparam>
</methodsynopsis>
<methodsynopsis language="python">
<methodname><link linkend="method-giocancellable--is-cancelled">is_cancelled</link></methodname>
<methodparam></methodparam>
</methodsynopsis>
<methodsynopsis language="python">
<methodname><link linkend="method-giocancellable--pop-current">pop_current</link></methodname>
<methodparam></methodparam>
</methodsynopsis>
<methodsynopsis language="python">
<methodname><link linkend="method-giocancellable--push-current">push_current</link></methodname>
<methodparam></methodparam>
</methodsynopsis>
<methodsynopsis language="python">
<methodname><link linkend="method-giocancellable--reset">reset</link></methodname>
<methodparam></methodparam>
</methodsynopsis>
<methodsynopsis language="python">
<methodname><link linkend="method-giocancellable--set-error-if-cancelled">set_error_if_cancelled</link></methodname>
<methodparam></methodparam>
</methodsynopsis>
</classsynopsis>
<programlisting>
<emphasis role="bold">Functions</emphasis>
<methodsynopsis language="python">
<methodname><link linkend="function-gio--cancellable-get-current">gio.cancellable_get_current</link></methodname>
<methodparam></methodparam>
</methodsynopsis></programlisting>
</refsect1>
<refsect1>
<title>Ancestry</title>
<synopsis>+-- <link linkend="class-gobject">gobject.GObject</link>
+-- <link linkend="class-giocancellable">gio.Cancellable</link>
</synopsis>
</refsect1>
<refsect1>
<title>Description</title>
<para>
The <link linkend="class-giocancellable"><classname>gio.Cancellable</classname></link>
is a thread-safe operation cancellation stack used throughout GIO to allow for
cancellation of synchronous and asynchronous operations.
</para>
</refsect1>
<refsect1 id="constructor-giocancellable">
<title>Constructor</title>
<programlisting><constructorsynopsis language="python">
<methodname>gio.Cancellable</methodname>
<methodparam></methodparam>
</constructorsynopsis></programlisting>
<variablelist>
<varlistentry>
<term><emphasis>Returns</emphasis> :</term>
<listitem><simpara>a new
<link linkend="class-giocancellable"><classname>gio.Cancellable</classname></link>.
</simpara></listitem>
</varlistentry>
</variablelist>
<para>
Creates a new <link linkend="class-giocancellable"><classname>gio.Cancellable</classname></link> object.
</para>
<para>
Applications that want to start one or more operations that should be cancellable should create a
<link linkend="class-giocancellable"><classname>gio.Cancellable</classname></link>
and pass it to the operations.
</para>
<para>
One <link linkend="class-giocancellable"><classname>gio.Cancellable</classname></link>
can be used in multiple consecutive operations, but not in multiple concurrent operations.
</para>
</refsect1>
<refsect1>
<title>Methods</title>
<refsect2 id="method-giocancellable--cancel">
<title>gio.Cancellable.cancel</title>
<programlisting><methodsynopsis language="python">
<methodname>cancel</methodname>
<methodparam></methodparam>
</methodsynopsis></programlisting>
<variablelist>
</variablelist>
<para>
The <methodname>cancel</methodname>() method will set cancellable to cancelled,
and will emit the "cancelled" signal. (However, see the warning about race conditions
in the documentation for that signal if you are planning to connect to it.)
</para>
<para>
This function is thread-safe. In other words, you can safely call it from a thread
other than the one running the operation that was passed the cancellable.
</para>
<para>
The convention within gio is that cancelling an asynchronous operation causes it
to complete asynchronously. That is, if you cancel the operation from the same thread
in which it is running, then the operation's GAsyncReadyCallback will not be invoked
until the application returns to the main loop.
</para>
</refsect2>
<refsect2 id="method-giocancellable--get-fd">
<title>gio.Cancellable.get_fd</title>
<programlisting><methodsynopsis language="python">
<methodname>get_fd</methodname>
<methodparam></methodparam>
</methodsynopsis></programlisting>
<variablelist>
<varlistentry>
<term><emphasis>Returns</emphasis> :</term>
<listitem><simpara>A valid file descriptor. -1 if the file descriptor
is not supported, or on errors.</simpara></listitem>
</varlistentry>
</variablelist>
<para>
The <methodname>get_fd</methodname>() method gets the file descriptor
for a cancellable job. This can be used to implement cancellable operations
on Unix systems. The returned fd will turn readable when cancellable is cancelled.
</para>
</refsect2>
<refsect2 id="method-giocancellable--is-cancelled">
<title>gio.Cancellable.is_cancelled</title>
<programlisting><methodsynopsis language="python">
<methodname>is_cancelled</methodname>
<methodparam></methodparam>
</methodsynopsis></programlisting>
<variablelist>
<varlistentry>
<term><emphasis>Returns</emphasis> :</term>
<listitem><simpara><literal>True</literal> if cancellable is cancelled,
<literal>False</literal> if called with <literal>None</literal> or if
item is not cancelled. </simpara></listitem>
</varlistentry>
</variablelist>
<para>
The <methodname>get_fd</methodname>() method gets the file descriptor
for a cancellable job. This can be used to implement cancellable operations
on Unix systems. The returned fd will turn readable when cancellable is cancelled.
</para>
</refsect2>
<refsect2 id="method-giocancellable--pop-current">
<title>gio.Cancellable.pop_current</title>
<programlisting><methodsynopsis language="python">
<methodname>pop_current</methodname>
<methodparam></methodparam>
</methodsynopsis></programlisting>
<variablelist>
</variablelist>
<para>
The <methodname>pop_current</methodname>() method pops cancellable off
the cancellable stack (verifying that cancellable is on the top of the stack).
</para>
</refsect2>
<refsect2 id="method-giocancellable--push-current">
<title>gio.Cancellable.push_current</title>
<programlisting><methodsynopsis language="python">
<methodname>push_current</methodname>
<methodparam></methodparam>
</methodsynopsis></programlisting>
<variablelist>
</variablelist>
<para>
The <methodname>push_current</methodname>() method pushes cancellable onto
the cancellable stack. The current cancllable can then be recieved using
<methodname><link linkend="function-gio--cancellable-get-current">gio.cancellable_get_current</link></methodname>().
</para>
</refsect2>
<refsect2 id="method-giocancellable--reset">
<title>gio.Cancellable.reset</title>
<programlisting><methodsynopsis language="python">
<methodname>reset</methodname>
<methodparam></methodparam>
</methodsynopsis></programlisting>
<variablelist>
</variablelist>
<para>
The <methodname>reset</methodname>() method resets cancellable to its uncancelled state.
</para>
</refsect2>
<refsect2 id="method-giocancellable--set-error-if-cancelled">
<title>gio.Cancellable.set_error_if_cancelled</title>
<programlisting><methodsynopsis language="python">
<methodname>set_error_if_cancelled</methodname>
<methodparam></methodparam>
</methodsynopsis></programlisting>
<variablelist>
<varlistentry>
<term><emphasis>Returns</emphasis> :</term>
<listitem><simpara><literal>True</literal> if cancellable was cancelled,
<literal>False</literal> if it was not.</simpara></listitem>
</varlistentry>
</variablelist>
<para>
The <methodname>set_error_if_cancelled</methodname>() method, if the cancellable
is cancelled, sets the error to notify that the operation was cancelled.
</para>
</refsect2>
</refsect1>
<refsect1>
<title>Functions</title>
<refsect2 id="function-gio--cancellable-get-current">
<title>gio.cancellable_get_current</title>
<programlisting><methodsynopsis language="python">
<methodname>cancellable_get_current</methodname>
<methodparam></methodparam>
</methodsynopsis></programlisting>
<variablelist>
<varlistentry>
<term><emphasis>Returns</emphasis> :</term>
<listitem><simpara>A <link linkend="class-giocancellable"><classname>gio.Cancellable</classname></link>
from the top of the stack, or <literal>None</literal> if the stack is empty.</simpara></listitem>
</varlistentry>
</variablelist>
<para>
The <methodname>cancellable_get_current</methodname>() function gets the top cancellable from the stack.
</para>
</refsect2>
</refsect1>
</refentry>
|
