Retired Document
Important: This document may not represent best practices for current development. Links to downloads and other resources may no longer be valid.
Icon Services Concepts
Icon Services provides icon data to multiple Mac OS clients, including the Finder, extensions and applications. Using Icon Services to obtain icon data means you can provide efficient icon caching and release memory when you don’t need icon data any longer. Icon Services provides the appropriate icon for any file object (file, folder, or volume), as well as other commonly used icons such as caution, note, or help icons in alert boxes, for example. The icons provided by Icon Services support a much larger palette of colors: up to 24 bits per pixel and an eight-bit mask. Icons are Appearance-compliant and appropriate to the active theme.
The IconRef
The basic data type used by Icon Services is the IconRef, a 32-bit opaque value. You obtain an IconRef by calling one of the GetIconRef functions described in Obtaining and Releasing IconRefs. Two or more files that have the same file type and creator and do not provide custom icons will use the same IconRef. Files with custom icons have their own IconRef.
Reference Counting
IconRef values are reference counted, so that the icon data represented by a particular IconRef can be shared by several clients simultaneously. Each client that uses a particular IconRef increments that IconRef’s reference count. When there are no more clients using a particular IconRef, the icon data associated with it is disposed of.
The 'icns' Resource
The 'icns' resource is a means of providing a single source for icon data, as opposed to the variety of icon resources represented by ‘ICN#’, ‘icl8’ and other familiar resource types. Combining all icon data into a single resource type speeds up icon fetching and simplifies resource management.
32-bit Icon Data
The 'icns' resource provides for 32-bit-deep icon data.
Deep Masks
Icons provided through the 'icns' resource feature deep masks, meaning an icon mask can have 256 different levels of transparency.
Huge Icons
The 'icns' resource adds “huge” icons, which are 48 pixels by 48 pixels, as well as providing the sizes contained in other icon resources. For more information, see 'icns'.
Copyright © 2003 Apple Computer, Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2003-02-01