<!-- ##### SECTION Title ##### -->
Input

<!-- ##### SECTION Short_Description ##### -->
Callbacks on file descriptors

<!-- ##### SECTION Long_Description ##### -->
<para>
The functions in this section are used to establish
callbacks when some condition becomes true for
a file descriptor. They are currently just wrappers around
the <link linkend="glib-IO-Channels">IO Channel</link>
facility.
</para>

<!-- ##### SECTION See_Also ##### -->
<para>
<variablelist>

<varlistentry>
<term><link linkend="glib-The-Main-Event-Loop">GLib Main Loop</link></term>
<listitem><para>The main loop in which input callbacks run.</para></listitem>
</varlistentry>

<varlistentry>
<term><link linkend="glib-IO-Channels">IO Channels</link></term>
<listitem><para>A newer and more flexible way of doing IO
callbacks.</para></listitem>
</varlistentry>

</variablelist>
</para>

<!-- ##### SECTION Stability_Level ##### -->


<!-- ##### FUNCTION gdk_input_add_full ##### -->
<para>
Establish a callback when a condition becomes true on
a file descriptor.
</para>

@source: a file descriptor.
@condition: the condition.
@function: the callback function.
@data: callback data passed to @function.
@destroy: callback function to call with @data when the input
  handler is removed.
@Returns: a tag that can later be used as an argument to
 gdk_input_remove().


<!-- ##### ENUM GdkInputCondition ##### -->
<para>
A set of bit flags used to specify conditions for which
an input callback will be triggered. The three members
of this enumeration correspond to the @readfds, 
@writefds, and @exceptfds arguments to the 
<function>select</function> system call.
</para>

@GDK_INPUT_READ: the file descriptor has become available for reading.
(Or, as is standard in Unix, a socket or pipe was closed
at the other end; this is the case if a subsequent read
on the file descriptor returns a count of zero.)
@GDK_INPUT_WRITE: the file descriptor has become available for writing.
@GDK_INPUT_EXCEPTION: an exception was raised on the file descriptor.

<!-- ##### USER_FUNCTION GdkInputFunction ##### -->
<para>
A callback function that will be called when some condition
occurs.
</para>

@data: the user data passed to gdk_input_add() or gdk_input_add_full().
@source: the source where the condition occurred.
@condition: the triggering condition.


<!-- ##### USER_FUNCTION GdkDestroyNotify ##### -->
<para>
A callback function called when a piece of user data is 
no longer being stored by GDK. Will typically free the
structure or object that @data points to.
</para>

@data: the user data.


<!-- ##### FUNCTION gdk_input_add ##### -->
<para>
Establish a callback when a condition becomes true on
a file descriptor.
</para>

@source: a file descriptor.
@condition: the condition.
@function: the callback function.
@data: callback data passed to @function.
@Returns: a tag that can later be used as an argument to
 gdk_input_remove().


<!-- ##### FUNCTION gdk_input_remove ##### -->
<para>
Remove a callback added with gdk_input_add() or 
gdk_input_add_full().
</para>

@tag: the tag returned when the callback was set up.


