Preview Components

Preview components create or display a preview of a QuickTime movie file. The preview is typically displayed as part of an Open File dialog; it is normally an image, but it may contain text, sound, or other data.

The preview may be contained in the movie file's resource fork, or it may be contained in the data fork of a "flattened" movie, or it may be created on the fly by the preview component whenever it is needed.

Applications do not normally interact with preview components directly. Preview services are available to applications through the movie toolbox and the image compression manager.

This chapter is primarily intended for developers who need to create a new preview component, but the sections " About Preview Components " and " New Features of Preview Components " may be of general interest to QuickTime developers.

About Preview Components

Inside Macintosh describes what preview components are, what they do, and how they are used.

New Features of Preview Components

QuickTime 4 Reference describes an enhancement to preview components, added as part of QuickTime 2.1, which allows them to work with previews stored in the data fork of a file, primarily for use on non-Macintosh computers. Also described is a new data structure that supports this functionality.

Creating Preview Components

Inside Macintosh describes the process of creating a preview component. A listing of a sample component is included.

Functions

Inside Macintosh describes the functions provided by preview components for displaying previews, handling events during a preview (such as playing a sound), and creating previews.

The Preview Resource

Inside Macintosh describes the preview resource, which is used to store a visual preview, and the preview resource item structure, which is an array that allows you to store additional preview information. QuickTime 4 Reference discusses storing the preview resource in the data fork, and defines a new data structure: PreviewResourceRecord.

Data Types

Inside Macintosh defines the component instance used by preview components, and lists the data structures for preview resources and the preview resource item structure. See also: " The Preview Resource " above, which includes the new PreviewResourceRecord data structure.

Constants

Inside Macintosh defines the constants that are used to communicate with preview components. These are primarily flags that describe the preview components capabilities and requirements.