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XtAppAddInput()						       XtAppAddInput()

Name
  XtAppAddInput	 - register a procedure to be called when there is activ‐
  ity on a file descriptor.

Synopsis
  XtInputId   XtAppAddInput(app_context,   source,    condition,    proc,
  client_data)
	 XtAppContext app_context;
	 int source;
	 XtPointer condition;
	 XtInputCallbackProc proc;
	 XtPointer client_data;

Inputs
  app_context
	    Specifies the application context.

  source    Specifies  the  file  descriptor (on a POSIX-based system) to
	    monitor.

  condition Specifies a mask that indicates a read, write,  or	exception
	    condition or some operating-system-dependent condition.

  proc	    Specifies  the  procedure that is to be called when condition
	    occurs on source.

  client_data
	    Specifies data to be passed to proc when it is invoked.

Returns
  A handle of type XtInputId that can be  passed  to  XtRemoveInput()  to
  unregister this input procedure.

Description
  XtAddInput()	registers  a  file  descriptor	source to be monitored by
  XtAppNextEvent()  and	 a  procedure  proc  to	 be  called   with   data
  client_data  when the condition (such as "input ready" or "error") con‐
  dition arises.

  On a POSIX-based system, the supported values for condition are XtInpu‐
  tReadMask, XtInputWriteMask, or XtInputExceptMask.  These values cannot
  be ORed together.  On non-POSIX systems, the types of source and condi‐
  tion will be operating-system dependent.

  See  XtInputCallbackProc(2) for an explanation of how to write an input
  callback.

  See the POSIX select() system call for more information on the possible
  file descriptor conditions that can be selected for.

Usage
  XtAppAddInput()  allows an Xt application to receive non-X based events
  through the same event loop that delivers X events.	File  descriptors
  in  POSIX are a very general mechanism, and XtAppAddInput() can be used
  to receive notification when the user types a command to stdin, when	a
  child	 process closes a pipe, or when there is data available on an RPC
  socket, for example.

  An input callback can be unregistered by  calling  XtRemoveInput()  and
  passing the XtInputId returned by this function.

  Note	that  when  reading  from  a socket, you should be careful not to
  close the end of the socket that is waiting before  exiting  XtAppMain‐
  Loop().   If	you  do this, you will get an infinite loop, in which the
  callback is called repeatedly, while the Intrinsics wait for an EOF  to
  be read.

Structures
  The XtInputId type is defined as follows:

     typedef unsigned long XtInputId;

See Also
  XtRemoveInput(1),
  XtInputCallbackProc(2).

Xt - Event Handling					       XtAppAddInput()

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