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tt_message_callback_add(library	call)	 tt_message_callback_add(library call)

NAME
       tt_message_callback_add -- register a callback function

SYNOPSIS
       #include	<Tt/tt_c.h>
       Tt_status tt_message_callback_add(
       Tt_message m,
       Tt_message_callback f);

DESCRIPTION
       The  tt_message_callback_add  function registers	a callback function to
       be automatically	invoked	by tt_message_receive(3) whenever a  reply  or
       other state-change to this message is returned.

       The  callback  is defined in Tt/tt_c.h -	Tttt_c(5). If the callback re-
       turns TT_CALLBACK_CONTINUE, other callbacks will	be run;	if no callback
       returns	TT_CALLBACK_PROCESSED, tt_message_receive returns the message.
       If the callback returns TT_CALLBACK_PROCESSED, no further callbacks are
       invoked for this	event; tt_message_receive does not return the message.

       The  m  argument	 is the	opaque handle for the message involved in this
       operation.  The f argument is the message callback to be	run.

       The pattern handle will be NULL if the message did not match a  dynamic
       pattern.	 This is usually the case for message callbacks.

RETURN VALUE
       Upon  successful	 completion,  the tt_message_callback_add function re-
       turns the status	of the operation as one	 of  the  following  Tt_status
       values:

       TT_OK	 The operation completed successfully.

       TT_ERR_NOMP
		 The ttsession(1) process is not running and the ToolTalk ser-
		 vice cannot restart it.

       TT_ERR_POINTER
		 The pointer passed does not point to an object	of the correct
		 type for this operation.

APPLICATION USAGE
       These  callbacks	are invoked from tt_message_receive; the program must,
       therefore, call tt_message_receive when the file	descriptor returned by
       tt_fd becomes active.

       The  application	can use	tt_message_callback_add	to create wrappers for
       ToolTalk	messages.  For example,	a library routine can construct	a  re-
       quest,  attach a	callback to the	message, send the message, and process
       the reply in the	callback.  When	the callback returns  TT_CALLBACK_PRO-
       CESSED, the message reply is not	returned to the	main program; the mes-
       sage and	reply are, therefore, completely hidden.

SEE ALSO
       Tt/tt_c.h - Tttt_c(5), tt_message_receive(3).

					 tt_message_callback_add(library call)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | APPLICATION USAGE | SEE ALSO

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