user manual

318 Chapter 14: Creating a User Interface Panel
Creating Callback Routines iTool Developer’s Guide
Creating Callback Routines
User interface panel callback routines are executed when an iTool component, for
which the panel has created an observer, generates a notification message. The
callback routine then uses the value of the notification message to determine what
action to take. Observers are created as described in “Adding Observers” on
page 315.
Callback Routine Signature
A user interface panel widget callback routine has the following signature:
PRO PanelName_callback , wPanel , IdOriginator , IdMessage , Value
where:
• PanelName_callback is the name of the callback routine,
• wPanel is the widget ID of the panel widget (see “About the Panel Widget” on
page 313),
• IdOriginator is a string identifying the source of the message (usually the
object identifier of an iTool component object, but it can be any string value),
• IdMessage is a string that uniquely identifies the message being sent, and
• Val ue is a value that is associated with the message being sent.
See “iTool Messaging System” on page 41 for more information on the IdMessage
and Valu e arguments.
Registration of Callback Routines
Callback routines are registered along with the user interface panel itself, in the call
to the RegisterWidget method of the IDLitUI object. See “Registering the Panel with
the User Interface Object” on page 314 for details.
Retrieving Widget State Information
The wPanel argument to the callback routine contains the widget ID of the panel
widget. This widget ID provides a way for the callback routine to retrieve state
information about the widgets that make up the panel.