Apple Newton Utilities User's Guide download pdf (Page 719)

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CHAPTER 19

Built-in Applications and System Data

System Data 19-45

Functions for Accessing User Conﬁguration Data 19

The global functions GetUserConfig and SetUserConfig get and set the

values of user conﬁguration variables in the system soup. These variables, see

“User Conﬁguration Variables” (page 16-101) in Newton Programmer’s Reference.

A list of these variables is available in the Summary; see 19 “User Conﬁguration

Var iab les.”

Your application can also register with the system to receive notiﬁcation of changes

to these variables. To do this, use the functions

RegUserConfigChange and

UnRegUserConfigChange described in Newton Programmer’s Reference.

IMPORTANT

The RegUserConfigChange global function registers a

callback function for execution in response to changes the user

conﬁguration variables. This callback function must not call

RegUserConfigChange or UnRegUserConfigChange. ▲

Storing Application Preferences in the System Soup 19

Each application that needs to save user preference or state information should

create a single entry in the system soup to store its data. Each entry in the system

soup must contain a slot named

tag whose value is a string uniquely identifying

the application to which the entry belongs. The system soup is indexed on the

tag

slot, allowing quick access to your application’s entry.

Use the utility function

GetAppPrefs to add your application’s preferences entry

to the system soup.

GetAppPrefs takes a default frame as a parameter, so you do

not need to create an entry in the system soup. The default is used if one doesn’t

already exist. The following sample code illustrates how this is done:

//define a default frame

constant kDefaultPrefs :=

'{curCity : "Cupertino",

//... and other application specific slots.

// Note: we do not include a 'tag slot,

// this will be added by GetAppPrefs.

}

// then when we have information to store...

ourPrefsEntry := GetAppPrefs(kAppSymbol, kDefaultPrefs);

ourPrefsEntry.curCity := newCity;

EntryChange(ourPrefsEntry);

The GetAppPrefs function is described in Newton Programmer’s Reference.

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