The Appearance Control Panel

The Appearance control panel is the user interface for the Appearance Manager. Through the Appearance control panel, users can adapt their experience of the system's look and sound by changing the current theme. The changes that the user makes to the current theme apply not just to the Mac OS itself, but also to all theme-compliant programs that the user is currently running.

Figure 2-1 shows the same desktop, before and after a change of themes.

Figure 2-1 The same desktop in two different themes

As Figure 2-1 shows, changing a theme can mean changing various user preferences. A theme can contain preferences for the current desktop picture or pattern, the system fonts, any interface-related sounds, the current appearance, and other options.

Each pane of the Appearance control panel allows the user to specify preferences for selected aspects of a theme. As shown in Figure 2-2 , the Themes pane is the first presented to the user. In this pane, the user can select the current theme from among various system-supplied themes, or the user can choose a theme that they themselves have previously created.

Figure 2-2 The Themes pane of the Appearance control panel

Figure 2-3 shows the Appearance pane of the Appearance control panel. In this pane, the user can select highlight and variation colors for an appearance. An appearance unifies the look of human interface objects on the system, including alert icons, controls, background colors, dialog boxes, menus, windows, and state transitions.

Figure 2-3 The Appearance pane of the Appearance control panel

In the Fonts pane of the Appearance control panel, shown in Figure 2-4 , the user can select the preferences for the system fonts in a theme. Note that the Appearance Manager distinguishes between large and small system fonts, as well as providing the user with the option to choose a separate views font for lists and labels, such as those used in Finder windows.

Figure 2-4 The Fonts pane of the Appearance control panel

As shown in Figure 2-5 , the user can change the current desktop picture or pattern via the Desktop pane of the Appearance control panel.

Figure 2-5 The Desktop pane of the Appearance control panel

Figure 2-6 shows the Sound pane of the Appearance control panel. Users can choose a "sound track" for any or all interface aspects in the current theme, or they can choose to eliminate interface sounds from the theme entirely.

Figure 2-6 The Sound pane of the Appearance control panel

In the Options pane of the Appearance control panel, shown in Figure 2-7 , the user can select scroll bar preferences and choose the window collapsing behavior for a theme.

When the user selects Smart Scrolling, double scroll bar arrows are used at one end of a scroll bar. For vertical scroll bars, the double arrows are located at the lower end of the scroll bar. For horizontal scroll bars, the double arrows are located at the right end of the scroll bar. The scroll box (also known as a "scroll indicator" or "thumb") is proportional in size to the amount of a window's visible content with smart scrolling.

If the user does not select smart scrolling, a single scroll bar arrow is used at each end of a scroll bar and the scroll box is of fixed size.

Figure 2-7 The Options pane of the Appearance control panel

While the Appearance control panel allows users to adapt their experience of the system's look and sound, some programs may also wish to set their own theme preferences, thus creating a custom theme environment in which to run. This is useful for some programs, such as games, that need to control the entire user environment while they are active. See Creating Custom Themes for more details on this process.

The Appearance Manager saves the preferences that describe a theme in a theme file in the System Folder. The Appearance Manager provides the following functions for working with theme files:

GetTheme obtains a collection containing data describing the current theme.
SetTheme sets a specified collection as the current theme.
IterateThemes iterates over all themes installed on a system.
IsValidAppearanceFileType returns whether the system can interpret files of a given file type as appearance files.