Apple 2 manual Error Handling, Error Correction

C H A P T E R 6

Data Input

When a user holds the pen on a key for a certain amount of time, the system acts as if the user were repeatedly tapping that key. This feature, called auto-repeat,affects character keys and modifier keys alike. Auto-repeat does not function during type-ahead. It operates only when the Newton system is ready to accept typing.

Error Handling

Applications need to strictly check user input for errors while providing several easy ways for users to correct their mistakes.

Error Correction

Users can edit their input with a common set of gestures (see “Editing” on page 6-21). In addition, tapping the Undo button reverses the effect of a user’s most recent action. Tapping Undo a second time undoes the undo.

The Newton interface elements provide undo capabilities for most user input. This includes writing, drawing, typing, correcting, editing, selecting a radio button, tapping a checkbox, setting a slider, and choosing from a picker of a labeled input line or expando.

Your application provides all other undo capabilities. For example, if a user chooses an item from an ordinary picker (not one that’s part of a labeled input line or expando), your application is responsible for letting the user undo the choice by tapping the Undo button. Undo should apply to a single recent action, not to a set of actions. Users should be able to undo individual actions taken in a slip, but once the slip is closed there is nothing to undo.

You don’t need to enable undo for every user action. In general, you should enable undo for actions that change data. You generally do not need to enable undo for actions that change the view of data or the environment, such as scrolling. From a user’s standpoint, the most desirable actions to have reversed by the Undo button are the actions that would be most difficult to reverse manually. You should consider the needs of your audience when deciding which actions can be undone.

Error Handling 6-37