MACROMEDIA FLASH 8-LEARNING ACTIONSCRIPT 2.0 IN FLASH Manual page 370

The following table contains brief descriptions of the new properties for movie clip instances:
Property
cacheAsBitmap
opaqueBackground Lets you specify a background color for the opaque movie clip
scrollRect
These three properties are independent of each other, however, the
properties work best when an object is cached as a bitmap. You only see
scrollRect
performance benefits for the
to
cacheAsBitmap true
To create a surface that's also scrollable, you must set the
properties for the movie clip instance. Surfaces can nest within other surfaces. The surface
copies the bitmap onto its parent surface.
For information on alpha channel masking, which requires you to set the
property to , see
true
You cannot apply caching directly to text fields. You need to place text within a movie
clip to take advantage of this feature. For an example, see the sample file in Flash install
directory\Samples and Tutorials\Samples\ActionScript\FlashType.
You can find a sample source file that shows you how bitmap caching can be applied to an
instance. Find the file called cacheBitmap.fla, in the Samples folder on your hard disk.
In Windows, browse to boot drive\Program Files\Macromedia\Flash 8\Samples and
Tutorials\Samples\ActionScript\CacheBitmap.
370 Working with Movie Clips
Description
Makes the movie clip instance cache a bitmap representation of itself.
Flash creates a surface object for the instance, which is a cached
bitmap instead of vector data. If you change the bounds of the movie
clip, the surface is recreated instead of resized. For more information
and an example, see
instance. If you set this property to a numeric value, the movie clip
instance has an opaque (nontransparent) surface. An opaque bitmap
does not have an alpha channel (transparency), and renders faster. For
more information and an example, see
movie clip" on page
Lets you quickly scroll movie clip content and have a window for
viewing larger content. The movie clip's contents are cropped, and the
instance scrolls with a specified width, height, and scroll offsets. This
lets the user quickly scroll movie clip content and have a window that
displays larger content than the Stage area. Text fields and complex
content that you display in the instance can scroll faster because Flash
does not regenerate the entire movie clip vector data. For more
information and an example, see
.
property)
opaqueBackground
.
"About alpha channel masking" on page
"Caching a movie clip" on page
"Setting the background of a
375.
scrollRect (MovieClip.scrollRect
and
scrollRect
cacheAsBitmap
377.
373.
and
opaqueBackground
properties when you set
and
scrollRect
cacheAsBitmap