ITT Rule IDL Version 7.0 User Manual download pdf (Page 356)

356 Chapter 15: Creating a Custom iTool Widget Interface

Handling Shutdown Events iTool Developer’s Guide

Handling Shutdown Events

Because your custom interface is associated with an iTool, destruction of the

interface may entail shutting down and cleaning up the entire iTools system. This

means that in addition to normal cleanup of pointers and objects used by the

interface, you will need to instruct the iTools system to shut itself down when your

interface is destroyed.

Generating Shutdown Events

You must set the TLB_KILL_REQUEST_EVENTS keyword when creating the top-

level widget base that holds your interface. With this keyword set, when the user

destroys the top-level base, a WIDGET_KILL_REQUEST event is generated,

allowing you to perform the actions necessary to shut down the iTools system.

Handling the Shutdown Event

When the user destroys the top-level base of your custom interface, you may want to

prompt the user to save the current iTool state before shutting down. The standard

iTool interface uses an iTool system service named “Shutdown” to both prompt the

user for confirmation that a shutdown is requested and offer to let the user save the

current state. The Shutdown service then handles other cleanup tasks before exiting

the iTool.

The following code, from the event handling routine in the

example2_wdtool.pro

interface definition (developed in “Example: a Custom iTool Interface” on page 360),

calls the iTools Shutdown service.

; Destroy the widget.

'WIDGET_KILL_REQUEST': BEGIN

; Get the shutdown service and call DoAction.

; This code must be here, and not in the _cleanup routine,

; because the tool may not actually be killed. (For example

; the user may be asked if they want to save, and they may

; hit "Cancel" instead.)

IF OBJ_VALID((*pState).oUI) THEN BEGIN

oTool = (*pState).oUI->GetTool()

oShutdown = oTool->GetService('SHUTDOWN')

void = (*pState).oUI->DoAction(oShutdown-

>getFullIdentifier())

ENDIF

END

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ITT Rule IDL Version 7.0 User Manual Page 356