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Inside the System File
(Continued)
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Icon Services
New for Mac OS 8.5, Icon Services provides fast
and efficient facilities for retrieval of appropriate
icon information used to represent files, directories, or
other commonly used icons (for example, the
caution alert icon, the note alert icon, and the help
icon).
- Icon Utilities is now implemented in PowerPC code.
(Icon Services is also native.)
- Icon Services is Appearance Manager-aware, and will
return information consistent with the active appearance
as appropriate. (If your program retrieves icons from the
System file via Icon Utilities or other means, these
icons will not differ according to appearance.)
- To avoid duplication of data and for better
performance, Icon Services maintains a system-wide icon
cache shared by all applications. Icon data returned is
common to all applications, so it is possible for two
different applications to obtain an icon reference that
refers to the same icon data. A reference count is
maintained for icons loaded into the cache, and icons are
removed from the cache only if the reference count falls
to zero.
- The new
'icns' resource contains data
for 4 icon sizes (mini, small, large, huge) at 4 color
depths (1-bit, 4-bit, 8-bit, and 32-bit) and two kind of
masks (1-bit masks and 8-bit masks). Deep (8 bit) masks
allow for the specification of transparent drawing
effects. Each pixel in a deep mask indicates the level of
transparancy desired for drawing a particular pixel.
Transparency levels range from 0 (transparent) through
255 (opaque).
- Prior to Mac OS 8.5, Icon Utilities allowed only 34
arbitrary colors to highlight properly (they were known
as the Apple icon colors). This limitation has been
removed.
- Drivers can now provide color icons by implementing
the
kdgMediaIconSuite Driver Gestalt
selector as described in the Device
Manager section.
Related Materials:
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