Specifications

83ADOBE FLEX 3
Building and Deploying Adobe Flex 3 Applications
The low setting favors playback speed over appearance and never uses anti-aliasing. The autolow setting empha-
sizes speed at first but improves appearance whenever possible. The
autohigh setting emphasizes playback speed
and appearance equally at first, but sacrifices appearance for playback speed if necessary. The
medium setting
applies some anti-aliasing and does not smooth bitmaps. The
high setting favors appearance over playback speed
and always applies anti-aliasing. The
best setting provides the best display quality and does not consider playback
speed. All output is anti-aliased and all bitmaps are smoothed.
For information on these settings, see “About the object and embed tags” on page 321.
Understanding redraw regions
A redraw region is the region around an object that must be redrawn when that object changes. Everything in a
redraw region is redrawn during the next rendering phase after an object changes. The area that Flash Player
redraws includes the object, and any objects that overlap with the redraw region, such as the background or the
object’s container.
You can see redraw regions at run time in the debugger version of Flash Player by selecting View > Show Redraw
Regions in the player’s menu. When you select this option, the debugger version of Flash Player draws red
rectangles around each redraw region while the application runs.
By looking at the redraw regions, you can get a sense of what is changing and how much rendering is occurring
while your application runs. Flash Player sometimes combines the redraw regions of several objects into a single
region that it redraws. As a result, if your objects are spaced close enough together, they might be redrawn as part
of one region, which is better than if they are redrawn separately. If the number of regions is too large, Flash Player
might redraw the entire screen.
Using the cacheAsBitmap property
To improve rendering speeds, make careful use of the cacheAsBitmap property. You can set this property on any
UIComponent.
When you set the
cacheAsBitmap property to true, Flash Player stores a copy of the initial bitmap image of an
object in memory. If you later need that object, and the object’s properties have not changed, Flash Player uses the
cached version to redraw the object. This can be faster than using the vectors that make up the object.
Setting the
cacheAsBitmap property to true can be especially useful if you use animations or other effects that
move objects on the screen. Instead of redrawing the object in each frame during the animation, Flash Player can
use the cached bitmap.
The downside is that changing the properties of objects that are cached as bitmaps is more computationally
expensive. Each time you change a property that affects the cached object’s appearance, Flash Player must remove
the old bitmap and store a new bitmap in the cache. As a result, only set the
cacheAsBitmap property to true for
objects that do not change much.