Normally measure will be called before layout occurs. If this doesn't happen, nothing is going to call it at all. An experimenting developer probably added a node to the hierarchy directly. We simply call measureWithSizeRange: using a size range equal to whatever bounds were provided to that element. This make initial experimentation using layoutSpecs much easier. Furthermore added logging if no size is given for the node before layout occurs.
Initial attempt to get display traits working with ASEnvironment.
To get proper ASDisplayTraits support, you must use an ASViewController. The ASViewController implements UITraitCollection-related methods (`traitCollectionDidChange:`, `willTransitionToTraitCollection:withTransitionCoordinator:`, viewWillTransitionToSize:withTransitionCoordinator`) to update the internal ASDisplayTraits and propagate them to subnodes.
ASTableNode and ASCollectionNode don't actually have their cells as subnodes, so a little bit of trickery is involved (on `setEnvironment:` the table/collection node gets its data controllers completedNodes and propagates the new traits. see `ASDisplayTraitsCollectionTableSetEnvironmentState`). The data controller also passes the current display traits when creating new cells.
ASViewController also supports the ability to return a custom set of display traits. So if you have a modal dialog that should always be told it is in a compact size class, you can set the override block before displaying the VC.
A new example, called Display Traits, has been added. It shows how display traits can be used in a ASViewController with a normal ASDisplayNode as its root, as well as in ASViewControllers hosting table nodes and collection nodes. There is also an example of overriding the default display traits of a VC.
Please provide feedback!
Summary:
We observed a deadlock which occurred when two threads were laying out the same set of nodes.
On one thread, layout would occur on a leaf node. It would lock and as part of this layout
process, ASDK walks up the node tree and calls __setNeedsLayout on its supernode until it
reaches the supernode with no supernode. When the supernode gets its call to __setNeedsLayout
it also locks. So leaf node locks and then awaits supernode lock.
On another thread, we're doing a layout pass on the supernode in the above thread. This locks
the supernode and attempts to lock the leaf node. This deadlocks (remember the above thread
is holding onto the leaf lock and awaiting the supernode lock. This thread is holding onto
the supernode lock and awaiting the leaf lock).
This is all exacerbated by the use of recursive locks.
- Remove defaults for ASEnvironmentLayoutOptionsState and ASEnvironmentHierarchyState
- Add locking for ASEnvironmentLayoutExtensibilityForwarding
- Other smaller improvements
- Refactor naming of ASEnvironmentCollection to ASEnvironmentState
- Remove struct pointers
- Move ASEnvironmentStatePropagation to a enum class
- Move merge functions to pure functions
- Move ASLayoutOptionsForwarding and ASLayoutableExtensibility into ASLayoutSpec and ASDisplayNode
- Remove ASLayoutableSetValuesForLayoutable and move into explicit classes (ASDisplayNode, ASTextNode)
[ASDisplayNode] Placeholders should always be recreated if returning to cleared nodes, and remain until ASNetwork/MultiplexImageNode finish loading their image from the network.
If previously-displayed contents is gone (e.g. clearContents), and is not finished displaying
by the time the node is onscreen, recreate the placeholder immediately.
