Newton Developer Technical Information: Newton Programmer's Guide: 2.1 OS Addendum /

Chapter 11 - Miscellaneous / Reference

Functions and Methods / Built-In Applications

RegUserConfigChange

RegUserConfigChange(callBackID, callBackFn)

Registers a function object to be called each time a user configuration variable changes.

callBackID

A unique symbol identifying the function object to be registered; normally, the value of this parameter is the application symbol, which includes your registered signature, or some variation on it.

callBackFn

A function object called when a user configuration variable changes. It is passed either one or two parameters. This function can be either of either of the following two forms:

func(changeSym, changeFrame) begin .... end

func(changeSym) begin .... end

On Newton devices where the *SetUserConfigEnMasse function is not defined, this callback function is always passed one argument. On Newton devices with *SetUserConfigEnMasse defined, this function will be called with the proper number of arguments; that is, if you define a one argument function, it will be called with only the changeSym argument, but if you define it with two arguments, it is called with both the changeSym and the changeFrame arguments.

For information on the changeSym and the changeFrame parameters, see SetUserConfing (in Newton Programmer's Reference) and SetUserConfingEnMasse.

The return value of callBackFn function is ignored.

return value

Undefined; do not rely on it.

DISCUSSION

Note that it is up to the application that changed one of these variables to broadcast the change. This is not something that you need to worry about, since the SetUserConfig function will always broadcast the change. Also note that the system may change, and broadcast the change of, certain undocumented user configuration variables; you should ignore these symbols.

SPECIAL CONSIDERATIONS

The function callBackFn must not call the *RegUserConfigChange or UnRegUserConfigChange functions.