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!
Grab a strong reference for asyncDataSource and asyncDelegate in ASCollectionView and ASTableView before executing the range update to be sure they are not going away while executing the range update. This can happen in range updates while going back in the view controller hierarchy
Unclear why the framework target required these seemingly unrelated changes to Collection
classes, but I modeled them after related files and it seems cleaner now (passes tests & framework target)
- Only update range mode if visibility changes if the node is not range controlled
- Only change explicitly set range mode if ASRangeController becomes visible
- Return interface state for range controller in ASCollectionView and ASTableView based on if the containing node is range managed
Introduces ASLayoutRangeModeVisibleOnly, allowing the preservation of decoded backing stores without any extra padding to
strictly minimize memory usage while supporting immediate re-display of content. Set visible range controllers to this mode
upon app suspend / memory warning, while more aggressively clearing others to the ASLayoutRangeModeLowMemory mode.
By default, when the app is running and recieves a memory warning, we set the range mode for non-visible controllers to
ASLayoutRangeModeVisibleOnly. This is because, unlike in the app suspend case where on app resume we can restore controllers
from LowMemory to VisibleOnly, the memory warning doesn't provide a good opportunity to do this.
A new +Beta API to control this behavior is called +setRangeModeForMemoryWarnings:, as some apps may prefer to use LowMemory
in the memory warning scenario. For these apps, optimal user experience will require manually setting the range mode back
to some larger value as the user navigates the app, or they will encounter controllers that are temporarily blank and need
a moment to re-display their contents as they start to become visible.
