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C H A P T E R 1 9
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
Variables."
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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