QuickTime 4 Reference

Selecting by Component Type Value

At the most basic level, your application can use the Component Manager's built-in selection mechanisms to find a data handler component for a data reference. You may use the Component Manager's FindNextComponent function in order to retrieve a list of all data handler components that meet your needs. You specify your request by supplying the component's characteristics in a component description record--in particular, in the componentType , componentSubtype , componentManufacturer , and componentFlags fields.

All data handler components have a component type value of 'dhlr' , which is defined by the dataHandlerType constant. Data handler components use the value of the component subtype field to indicate the type of data reference they support. As a result of this convention, note that all data handlers that share a component subtype value must be able to recognize and work with data references of the same type. For example, file system data handlers always carry a component subtype value of 'alis' , which indicates that their data references are file system aliases (note that this is true for QuickTime on the Macintosh and under Windows, even though there is not, properly, a file system alias under Windows). Apple's memory-based data handler for the Macintosh has a component subtype value of 'hndl' .

Apple has not defined any special manufacturer field values or component flags values for data handler components. You may use the manufacturer field to select data handlers supplied by a specific vendor. To do so, you need to know the correct manufacturer field value for that vendor.