The rectangle parameter is currently not used --- all callers always pass the full canvas bounds. In the long term,
we probably won't want this parameter since all implementations should be doing accelerated drawing direct to buffers
with no intermediate copies, hence there will be no need to optimize the size of those copies. Plus, performance-sensitive
testcases tend to paint most or all of the canvas on every frame anyway.
The rectangle parameter is currently not used --- all callers always pass the full canvas bounds. In the long term,
we probably won't want this parameter since all implementations should be doing accelerated drawing direct to buffers
with no intermediate copies, hence there will be no need to optimize the size of those copies. Plus, performance-sensitive
testcases tend to paint most or all of the canvas on every frame anyway.
