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Initial attempt at implementing Display Traits

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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!
This commit is contained in:
rcancro
2016-04-25 16:59:00 -07:00
parent 495f32f0ef
commit 8bb4eba080
37 changed files with 1535 additions and 68 deletions
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64
AsyncDisplayKit/Details/ASEnvironment.h
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@@ -14,6 +14,8 @@
#import "ASStackLayoutDefines.h"
#import "ASRelativeSize.h"
@protocol ASEnvironment;
@class UITraitCollection;
ASDISPLAYNODE_EXTERN_C_BEGIN
NS_ASSUME_NONNULL_BEGIN
@@ -59,17 +61,50 @@ typedef struct ASEnvironmentHierarchyState {
unsigned layoutPending:1; // = NO
} ASEnvironmentHierarchyState;
#pragma mark - ASDisplayTraits
typedef struct ASDisplayTraits {
CGFloat displayScale;
UIUserInterfaceSizeClass horizontalSizeClass;
UIUserInterfaceIdiom userInterfaceIdiom;
UIUserInterfaceSizeClass verticalSizeClass;
UIForceTouchCapability forceTouchCapability;
// WARNING:
// This pointer is in a C struct and therefore not managed by ARC. It is
// an unsafe unretained pointer, so when you dereference it you better be
// sure that it is valid.
//
// Use displayContext when you wish to pass view context specific data along with the
// trait collcetion to subnodes. This should be a piece of data owned by an
// ASViewController, which will ensure that the data is still valid when laying out
// its subviews. When the VC is dealloc'ed, the displayContext it created will also
// be dealloced but any subnodes that are hanging around (why would they be?) will now
// have a displayContext that points to a bad pointer.
//
// An added precaution is to call ASDisplayTraitsClearDisplayContext from your ASVC's desctructor
// which will propagate a nil displayContext to its subnodes.
//__unsafe_unretained id displayContext;
id __unsafe_unretained displayContext;
} ASDisplayTraits;
extern void ASDisplayTraitsClearDisplayContext(id<ASEnvironment> rootEnvironment);
extern ASDisplayTraits ASDisplayTraitsFromUITraitCollection(UITraitCollection *traitCollection);
extern BOOL ASDisplayTraitsIsEqualToASDisplayTraits(ASDisplayTraits displayTraits0, ASDisplayTraits displayTraits1);
#pragma mark - ASEnvironmentState
typedef struct ASEnvironmentState {
struct ASEnvironmentHierarchyState hierarchyState;
struct ASEnvironmentLayoutOptionsState layoutOptionsState;
struct ASDisplayTraits displayTraits;
} ASEnvironmentState;
extern ASEnvironmentState ASEnvironmentStateMakeDefault();
ASDISPLAYNODE_EXTERN_C_END
@class ASTraitCollection;
#pragma mark - ASEnvironment
@@ -93,6 +128,33 @@ ASDISPLAYNODE_EXTERN_C_END
/// Classes should implement this method and return YES / NO dependent if upward propagation is enabled or not
- (BOOL)supportsUpwardPropagation;
/// Classes should implement this method and return YES / NO dependent if downware propagation is enabled or not
- (BOOL)supportsDownwardPropagation;
@end
NS_ASSUME_NONNULL_END
// ASCollection/TableNodes don't actually have ASCellNodes as subnodes. Because of this we can't rely on display trait
// downward propagation via ASEnvironment. Instead if the new environmentState has displayTraits that are different from
// the cells', then we propagate downward explicitly and request a relayout.
//
// If there is any new downward propagating state, it should be added to this define.
//
// This logic is used in both ASCollectionNode and ASTableNode
#define ASDisplayTraitsCollectionTableSetEnvironmentState \
- (void)setEnvironmentState:(ASEnvironmentState)environmentState\
{\
ASDisplayTraits oldDisplayTraits = self.environmentState.displayTraits;\
[super setEnvironmentState:environmentState];\
ASDisplayTraits currentDisplayTraits = environmentState.displayTraits;\
if (ASDisplayTraitsIsEqualToASDisplayTraits(currentDisplayTraits, oldDisplayTraits) == NO) {\
NSArray<NSArray <ASCellNode *> *> *completedNodes = [self.view.dataController completedNodes];\
for (NSArray *sectionArray in completedNodes) {\
for (ASCellNode *cellNode in sectionArray) {\
ASEnvironmentStatePropagateDown(cellNode, currentDisplayTraits);\
[cellNode setNeedsLayout];\
}\
}\
}\
}\
NS_ASSUME_NONNULL_END