For https://github.com/flutter/flutter/issues/33807
We still need to make layers' children immutable for full immutability.
That will require us to change the SceneBuilder API to build the layer
bottom up instead of top down (post-order traversal instead of pre-order
traversal).
This will further guard that the framework won't forget to set the
clip behavior.
This has been tested with the flutter/flutter framework
`flutter test --local-engine=host_debug_unopt`
to ensure a successful engine roll.
This PR replaces the unused `PrerollContext::child_paint_bounds` with `PrerollContext::cull_rect` so we can prune unnecessary preroll tasks (especially cache) based on clips. This PR fixes https://github.com/flutter/flutter/issues/24712
Performance test has been added (https://github.com/flutter/flutter/pull/25381) to make sure that we won't regress again in the future.
Note that the cull_rect here is very similar to those removed in https://github.com/flutter/engine/pull/6352 . We can't compute cull rects in SceneBuilder because of retained layers. But we can still compute and use them to optimize performance in Preroll.
The overlay surfaces are going to be the same IOSSurface implementation
with the platform views controller set to null (so these are surfaces
that don't support embedding platform views to them).
* Adds a FlutterOverlayView which is a UIView that's showing an
overlay surface.
* Creates an overlay surface for each embedded UIView (done in
FlutterPlatformViewsController).
* Changes CompositeEmbeddedView to return a new canvas.
* Makes the PlatformViewLayer replace the PaintContext's canvas with
the canvas for the overlay view.
* Changed canvas in PaintContext to be a pointer so it can be changed.
TBD in following PRs:
* Copy the current canvas state when replacing a canvas in PaintContext.
* Make FlutterOverlayView work with a GL backend (currently it only
works with software rendering)
saveLayer is slow so we should avoid it as much as possible. If
there are artifacts without saveLayer, then we should report that
to Skia for the fix instead of slowing the performance with
saveLayer.
This PQ makes average rasterizer time drop from 25ms to 18ms in
flutter_gallery transitions perf test on a Nexus 5X.
This partially fixesflutter/flutter#13736 .
We probably still need some work in the opacity layer to squize
all the performance improvements.
We push a bit up the tree during preroll to learn whether there system
composited layers below each layer. During update scene, we squash down
to paint tasks, which we execute after publishing the new scene.
Instead, make Layer::Paint take a new PaintContext that has just exactly
the state that it needs, mirroring PrerollContext. Also, rename
PaintContext to CompositorContext because it holds the context for the
whole compositor.
