Apple Newton Utilities User's Guide download pdf (Page 640)

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101

CHAPTER 17

Additional System Services

17-24 Using Additional System Services

Because the ViewSet method rebuilds and updates all the status slip’s child views,

you’ll obtain better performance by calling

UpdateIndicator

rather than

ViewSet when you just need to update the gauge view. The

UpdateIndicator method rebuilds and updates only the gauge, barber pole, and

progress sheet views.

Implementing a CancelRequest Method 17

If your status slip provides a “Stop” or “Cancel” button, you may include a

ButtonClickScript with the button or write a CancelRequest method to

handle the necessary housekeeping. The

CancelRequest method can be

implemented either in the status slip or in the application (or transport) base view.

The system checks if the status slip has a

CancelRequest method, and if not

sends this message to the application (or transport) base view.

Using the Power Registry 17

This section describes the cooperative model that Newton devices use to turn

power on and off, and the battery information functions.

Registering Power-On Functions 17

You may register functions to be called when a Newton device is powered on with

the

RegPowerOn function. When the Newton device is powered on, the system

calls your “power-on” callback function passing it a symbol indicating the reason it

was called. This allows your code to condition its actions accordingly. For example,

you might perform one set of actions when the user presses the power switch and

another set of actions when the device is powered on by the execution of an alarm.

The

'user symbol indicates that the user pressed the power switch. The

'emergencyPowerOn symbol is passed any time the Newton device is powered

up after an emergency power-off. An emergency power-off is any shutdown in

which one or more power-off scripts did not execute. The

'serialgpi symbol

indicates the presence of +5 volts on the serial port general-purpose input pin (pin

7). The

'alarm symbol indicates that the power-on was caused by the execution

of an alarm. The

'cardlock symbol indicates that a PCMCIA card was inserted

or removed.

The

UnRegPowerOn function unregisters functions added with RegPowerOn.

IMPORTANT

The callback function registered with RegPowerOn must not

itself call

RegPowerOn nor UnRegPowerOn. ▲

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Apple Newton Utilities User's Guide Page 640

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