* make variable naming reflect ASEnvironmentTraitCollection vs ASTraitCollection
* move trait propagation to cell allocation instead of via a nested block
* move trait propagation when setting a displaynode's supernode instead of when adding a subnode
* fixed misspelling of "colection"
* Fixed bug in `ASEnvironmentMergeObjectAndState`
* New ASLayoutSpec methods for `setChild`/`setChildren`/`setChild:forIdentifier:` have been added to take in a trait collection.
* Added `setChild:`-like methods for ASLayoutSpecs take a traitCollection
* Fixed instances where nodes in a data controller were not getting their trait collections
* propagate traitCollection in ASDisplayNode on insertSubnode or addSubnode
In _layoutNodesFromContexts:ofKind:completion: we pass the full array of contexts to _layoutNodes:fromContexts:atIndexesOfRange:ofKind: but for nodes we pass a subarray of nodes instead based on the batchCount. As batchRange we always start from 0 to batchCount. We now use the same indexes that we use to create the subarray of nodes to get a subarray of contexts that we pass to _layoutNodes:fromContexts:atIndexesOfRange:ofKind:.
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!
We move from block based enumeration for the array to fast enumeration as from a benchmark perspective this is faster. For the dictionary we stay with block based enumeration as looking up the value for the key in e.g. fast enumeration would be slower as using the block based API where we get the key and value for passed in
- _populateFromDataSourceWithSectionIndexSet doesn't accept a mutanle array but allocate one itself.
- Remove _populateFromEntireDataSourceWithMutableContexts.
- ASIndexedNodeContext executes its block, nil out the block and return the result.
- It is a container object that holds enough information to construct and measure a cell node
- All information is gathered on main thread. This allows ASDataController to capture the correct state of its data source before going to background.
These optimizations are surprisingly impactful. -setNeedsDisplay being called
for every node triggered cancelAsyncDisplay, locking, and memory management overhead
that is completely avoidable because Core Animation triggers first display automatically.
The mutable array copy optimizations reduced this key cost by over 10x, from 52ms to 5ms
on an iPad Air 2 / A8X with a real-world test case.
The optimization seems correct now, but apps like Pinterest have some core code relying on edit operation
order that is actually not permitted by UIKit (and this diff) but were tolerated previously. We will
re-land this once we have time to adapt the code.
