C H A P T E R 8

User Input

Figure 8-3 Primary highlight color on child item; secondary color on parent

Secondary highlight color

Primary highlight color

Focus ring

Pressing the Tab key navigates between controls. Shift-Tab navigates in the reverse direction. The arrow keys provide navigation within controls. In list views, the Right Arrow and Left Arrow keys open and close disclosure triangles.

Type-Ahead and Key-Repeat

When the user types faster than the computer can handle or when the computer is unable to process the keystrokes, the keystrokes are queued for later processing. This queuing is called type-ahead. There is a limit (varying with the computer) to the number of keystrokes that can be queued, but it’s usually not reached unless the user types while the application is performing a lengthy operation.

When a character key is held down for a certain amount of time, it starts repeating automatically. The user can make adjustments to this feature, called key-repeat, in Keyboard & Mouse preferences.

An application can tell whether keystrokes are generated by key-repeat or by the same key being pressed numerous times. Your application can disregard key-repeat keystrokes; it should ignore them in keyboard shortcuts that begin with the Command key.

Key-repeat works only when the application is ready to accept keyboard input; it does not function during type-ahead.

Selecting

Before performing an operation on an object, the user must select it to distinguish it from other objects. There is always immediate visual feedback to show that something is selected.

Selecting an object never alters the object itself, and a selection is always undoable by clicking outside the selection.

How something is selected depends on what it is. It’s useful to distinguish among three types of objects that are each dealt with in a different way when selected:

108 Selecting

2008-06-09 | © 1992, 2001-2003, 2008 Apple Inc. All Rights Reserved.