* Small changes required by the layout debugger
- `ASDisplayNode` can be told to not flatten its layout immediately but later on. The unflattened layout is also stored in a separate property. It's needed for inspecting not only display nodes but also layout specs used to compute a layout tree.
- `ASLayout` can be told to always retain its sublayout elements. This is needed especially for layout specs since they are usually not retained after an ASLayout was computed.
* Update CHANGELOG
* Address comments
* [Yoga] Implement ASYogaLayoutSpec, an experimental alternative to full-tree integration.
This approach allows us to avoid any ASDisplayNode.mm integration points.
However, it is not yet proven to be possible to achieve correctness with this approach.
The entry point (to start calculating), and the measurement function inputs, lack
the full expressiveness of ASSizeRange; we need to make sure that workarounds like
using style.minSize are successful in simulating the behavior of a full Yoga tree.
* [Yoga] Fix file comments, move towards <ASLayoutElement> support.
* [Yoga] Important fix for simplified, non-contiguous Yoga integration.
* [Yoga] Complete implementation of manual memory management (__bridge_transfer, YGNodeFree)
* [ASDisplayNode] Convert isSynchronous to an Objective-C atomic BOOL.
This reduces lock contention, and should also fix a very rarely seen deadlock.
* [ASDisplayNode] Implement a std::atomic-based flag system for superb performance
Although Objective-C atomics are equally fast, or better that std::atomic when
access through method calls, for the most intense use cases it is best to avoid
method calls entirely.
In ASDisplayNode, we could benefit significantly from avoiding both method calls
(already true today) but also avoid locking the mutex, for both CPU and contention
gains.
There will still be many methods that need locking for transactional
consistency - however, there are currently dozens of accessor methods that could
avoid frequent lock / unlock cycles with use of atomics, and other usages of the
ivars directly where locking could be delayed until after early-return conditions
are checked and passed.
We have to check in this case if the supernode of the subnode is indeed the _node that executes a layout transition. It can happen that a node already did a layout transition and added this subnode, in this case the subnode would would be removed from the new node instead of _node.
