DESIGN (xvwidgets) functions


LIBRARY ROUTINE

xvw_add_callback - add a callback to a GUI object

LIBRARY CALL

void xvw_add_callback(
   xvobject   object,
   char       *type,
   void       (*callback_routine)(xvobject, kaddr, kaddr),
   kaddr      client_data)

INPUT

OUTPUT

none

RETURN VALUE

none

DESCRIPTION

Installs a callback on a GUI object. When the GUI object is used as specified by the type argument, the callback will be called.

A callback must be defined as follows: void callback( xvobject object, kaddr client_data, kaddr call_data)

object - The GUI object for which the callback was invoked.

client_data - The pointer to the private client data, used to pass parameters from the application to the callback routine. call_data - The call_data is the mechanism through which the GUI object itself can pass parameters to a callback when * ! applicable. The structure type of the call_data is defined by the GUI object; it must be cast to its correct structure type before being used in the callback. Please see the documentation on the particular GUI object of interest for the definition and use of the call_data pointer by a particular GUI object.

ADDITIONAL INFORMATION

none

EXAMPLES

none

SIDE EFFECTS

none

RESTRICTIONS

none

MODIFICATION

none

FILES

$DESIGN/objects/library/xvwidgets/src/callback.c

SEE ALSO

xvwidgets(3)

COPYRIGHT

Copyright (C) 1993 - 1997, Khoral Research, Inc. ("KRI") All rights reserved.