Previously, display lists were used only if hardware acceleration
was enabled for an application (hardwareAccelerated=true) *and* if
setDrawingCacheEnabled(true) was called. This change makes the framework
use display lists for all views in an application if hardware acceleration
is enabled.
In addition, display list renderering has been optimized so that
any view's recreation of its own display list (which is necessary whenever
the visuals of that view change) will not cause any other display list
in its parent hierarchy to change. Instead, when there are any visual
changes in the hierarchy, only those views which need to have new
display list content will recreate their display lists.
This optimization works by caching display list references in each
parent display list (so the container of some child will refer to its
child's display list by a reference to the child's display list). Then when
a view needs to recreate its display list, it will do so inside the same
display list object. This will cause the content to get refreshed, but not
the reference to that content. Then when the view hierarchy is redrawn,
it will automatically pick up the new content from the old reference.
This optimization will not necessarily improve performance when applications
need to update the entire view hierarchy or redraw the entire screen, but it does
show significant improvements when redrawing only a portion of the screen,
especially when the regions that are not refreshed are complex and time-
consuming to redraw.
Change-Id: I68d21cac6a224a05703070ec85253220cb001eb4
47ab362e8d