[ASDisplayNode] Provide safeAreaInsets and layoutMargins bridge (#685)

* [ASDisplayNode] Add safeAreaInsets, layoutMargins and related properties to ASDisplayNode

* Add layoutMargins bridged to the underlying view

* Add safeAreaInsets bridged to the underlying view

* Add fallback calculation of safeAreaInsets for old iOS versions

* Add automaticallyRelayoutOnSafeAreaChanges and automaticallyRelayoutOnLayoutMarginsChanges properties

* Add additionalSafeAreaInsets property to ASViewController for compatibility with old iOS versions

* Provide safeAreaInsets for layer-backed nodes.

This also fixes tests.

* Fix crash when insetsLayoutMarginsFromSafeArea is set from a background thread

* Changes requested at code review:
* Update documentation for layoutMargins and safeAreaInsets properties. Suggest that users set the automaticallyRelayout* flags to ensure that their layout is synchronized to the margin's values.
* Fix accessing ASDisplayNode internal structures without a lock.
* Add shortcut in -[ASDisplayNode _fallbackUpdateSafeAreaOnChildren] to skip a child when possible.
* Add shortcut in ASViewController to avoid fallback safe area insets recalculation in iOS 11. Fix fallback safe area insets recalculation when the additionalSafeAreaInsets are set.
* Add debug check that a view controller's node is never reused without its view controller, so the viewControllerRoot flag value is always consistent.
* Use getters instead of reading ivars directly in -layoutMarginsDidChange and -safeAreaInsetsDidChange.

* Minor change in CHANGELOG

* Minor change in ASDisplayNodeTests.mm

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## master
 * Add your own contributions to the next release on the line below this with your name.
+- [ASDisplayNode] Add safeAreaInsets, layoutMargins and related properties to ASDisplayNode, with full support for older OS versions [Yevgen Pogribnyi](https://github.com/ypogribnyi) [#685](https://github.com/TextureGroup/Texture/pull/685)
 - [ASPINRemoteImageDownloader] Allow cache to provide animated image. [Max Wang](https://github.com/wsdwsd0829) [#850](https://github.com/TextureGroup/Texture/pull/850)
 - [tvOS] Fixes errors when building against tvOS SDK [Alex Hill](https://github.com/alexhillc) [#728](https://github.com/TextureGroup/Texture/pull/728)
 - [ASDisplayNode] Add unit tests for layout z-order changes (with an open issue to fix).

Source/ASDisplayNode.h

@@ -551,6 +551,20 @@ extern NSInteger const ASDefaultDrawingPriority;
  */
 @property (nonatomic, readonly) BOOL supportsLayerBacking;
 
+/**
+ * Whether or not the node layout should be automatically updated when it receives safeAreaInsetsDidChange.
+ *
+ * Defaults to NO.
+ */
+@property (nonatomic, assign) BOOL automaticallyRelayoutOnSafeAreaChanges;
+
+/**
+ * Whether or not the node layout should be automatically updated when it receives layoutMarginsDidChange.
+ *
+ * Defaults to NO.
+ */
+@property (nonatomic, assign) BOOL automaticallyRelayoutOnLayoutMarginsChanges;
+
 @end
 
 /**
@@ -725,6 +739,33 @@ extern NSInteger const ASDefaultDrawingPriority;
 @property (nonatomic, assign)           BOOL autoresizesSubviews;              // default==YES (undefined for layer-backed nodes)
 @property (nonatomic, assign)           UIViewAutoresizing autoresizingMask;   // default==UIViewAutoresizingNone (undefined for layer-backed nodes)
 
+/**
+ * @abstract Content margins
+ *
+ * @discussion This property is bridged to its UIView counterpart.
+ *
+ * If your layout depends on this property, you should probably enable automaticallyRelayoutOnLayoutMarginsChanges to ensure
+ * that the layout gets automatically updated when the value of this property changes. Or you can override layoutMarginsDidChange
+ * and make all the necessary updates manually.
+ */
+@property (nonatomic, assign)           UIEdgeInsets layoutMargins;
+@property (nonatomic, assign)           BOOL preservesSuperviewLayoutMargins;  // default is NO - set to enable pass-through or cascading behavior of margins from this view’s parent to its children
+- (void)layoutMarginsDidChange;
+
+/**
+ * @abstract Safe area insets
+ *
+ * @discussion This property is bridged to its UIVIew counterpart.
+ *
+ * If your layout depends on this property, you should probably enable automaticallyRelayoutOnSafeAreaChanges to ensure
+ * that the layout gets automatically updated when the value of this property changes. Or you can override safeAreaInsetsDidChange
+ * and make all the necessary updates manually.
+ */
+@property (nonatomic, readonly)         UIEdgeInsets safeAreaInsets;
+@property (nonatomic, assign)           BOOL insetsLayoutMarginsFromSafeArea;  // Default: YES
+- (void)safeAreaInsetsDidChange;
+
+
 // UIResponder methods
 // By default these fall through to the underlying view, but can be overridden.
 - (BOOL)canBecomeFirstResponder;                                            // default==NO

Source/ASDisplayNode.mm

@@ -282,6 +282,14 @@ - (void)_initializeInstance
 
   _flags.canClearContentsOfLayer = YES;
   _flags.canCallSetNeedsDisplayOfLayer = YES;
+
+  _fallbackSafeAreaInsets = UIEdgeInsetsZero;
+  _fallbackInsetsLayoutMarginsFromSafeArea = YES;
+  _isViewControllerRoot = NO;
+
+  _automaticallyRelayoutOnSafeAreaChanges = NO;
+  _automaticallyRelayoutOnLayoutMarginsChanges = NO;
+
   ASDisplayNodeLogEvent(self, @"init");
 }
 
@@ -851,7 +859,104 @@ - (void)nodeViewDidAddGestureRecognizer
   _flags.viewEverHadAGestureRecognizerAttached = YES;
 }
 
-#pragma mark UIResponder
+- (UIEdgeInsets)fallbackSafeAreaInsets
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  return _fallbackSafeAreaInsets;
+}
+
+- (void)setFallbackSafeAreaInsets:(UIEdgeInsets)insets
+{
+  BOOL needsManualUpdate;
+  BOOL updatesLayoutMargins;
+
+  {
+    ASDN::MutexLocker l(__instanceLock__);
+    ASDisplayNodeAssertThreadAffinity(self);
+
+    if (UIEdgeInsetsEqualToEdgeInsets(insets, _fallbackSafeAreaInsets)) {
+      return;
+    }
+
+    _fallbackSafeAreaInsets = insets;
+    needsManualUpdate = !AS_AT_LEAST_IOS11 || _flags.layerBacked;
+    updatesLayoutMargins = needsManualUpdate && [self _locked_insetsLayoutMarginsFromSafeArea];
+  }
+
+  if (needsManualUpdate) {
+    [self safeAreaInsetsDidChange];
+  }
+
+  if (updatesLayoutMargins) {
+    [self layoutMarginsDidChange];
+  }
+}
+
+- (void)_fallbackUpdateSafeAreaOnChildren
+{
+  ASDisplayNodeAssertThreadAffinity(self);
+
+  UIEdgeInsets insets = self.safeAreaInsets;
+  CGRect bounds = self.bounds;
+
+  for (ASDisplayNode *child in self.subnodes) {
+    if (AS_AT_LEAST_IOS11 && !child.layerBacked) {
+      // In iOS 11 view-backed nodes already know what their safe area is.
+      continue;
+    }
+
+    if (child.viewControllerRoot) {
+      // Its safe area is controlled by a view controller. Don't override it.
+      continue;
+    }
+
+    CGRect childFrame = child.frame;
+    UIEdgeInsets childInsets = UIEdgeInsetsMake(MAX(insets.top    - (CGRectGetMinY(childFrame) - CGRectGetMinY(bounds)), 0),
+                                                MAX(insets.left   - (CGRectGetMinX(childFrame) - CGRectGetMinX(bounds)), 0),
+                                                MAX(insets.bottom - (CGRectGetMaxY(bounds) - CGRectGetMaxY(childFrame)), 0),
+                                                MAX(insets.right  - (CGRectGetMaxX(bounds) - CGRectGetMaxX(childFrame)), 0));
+
+    child.fallbackSafeAreaInsets = childInsets;
+  }
+}
+
+- (BOOL)isViewControllerRoot
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  return _isViewControllerRoot;
+}
+
+- (void)setViewControllerRoot:(BOOL)flag
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  _isViewControllerRoot = flag;
+}
+
+- (BOOL)automaticallyRelayoutOnSafeAreaChanges
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  return _automaticallyRelayoutOnSafeAreaChanges;
+}
+
+- (void)setAutomaticallyRelayoutOnSafeAreaChanges:(BOOL)flag
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  _automaticallyRelayoutOnSafeAreaChanges = flag;
+}
+
+- (BOOL)automaticallyRelayoutOnLayoutMarginsChanges
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  return _automaticallyRelayoutOnLayoutMarginsChanges;
+}
+
+- (void)setAutomaticallyRelayoutOnLayoutMarginsChanges:(BOOL)flag
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  _automaticallyRelayoutOnLayoutMarginsChanges = flag;
+}
+
+#pragma mark - UIResponder
 
 #define HANDLE_NODE_RESPONDER_METHOD(__sel) \
   /* All responder methods should be called on the main thread */ \
@@ -1042,6 +1147,8 @@ - (void)__layout
       [self layoutDidFinish];
     });
   }
+
+  [self _fallbackUpdateSafeAreaOnChildren];
 }
 
 - (void)layoutDidFinish

Source/ASViewController.h

@@ -78,6 +78,11 @@ NS_ASSUME_NONNULL_BEGIN
 // Refer to examples/SynchronousConcurrency, AsyncViewController.m
 @property (nonatomic, assign) BOOL neverShowPlaceholders;
 
+/* Custom container UIViewController subclasses can use this property to add to the overlay
+ that UIViewController calculates for the safeAreaInsets for contained view controllers.
+ */
+@property(nonatomic) UIEdgeInsets additionalSafeAreaInsets;
+
 @end
 
 @interface ASViewController (ASRangeControllerUpdateRangeProtocol)

Source/ASViewController.mm

@@ -32,6 +32,7 @@ @implementation ASViewController
   NSInteger _visibilityDepth;
   BOOL _selfConformsToRangeModeProtocol;
   BOOL _nodeConformsToRangeModeProtocol;
+  UIEdgeInsets _fallbackAdditionalSafeAreaInsets;
 }
 
 - (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
@@ -73,10 +74,14 @@ - (void)_initializeInstance
   if (_node == nil) {
     return;
   }
+
+  _node.viewControllerRoot = YES;
 
   _selfConformsToRangeModeProtocol = [self conformsToProtocol:@protocol(ASRangeControllerUpdateRangeProtocol)];
   _nodeConformsToRangeModeProtocol = [_node conformsToProtocol:@protocol(ASRangeControllerUpdateRangeProtocol)];
   _automaticallyAdjustRangeModeBasedOnViewEvents = _selfConformsToRangeModeProtocol || _nodeConformsToRangeModeProtocol;
+
+  _fallbackAdditionalSafeAreaInsets = UIEdgeInsetsZero;
 
   // In case the node will get loaded
   if (_node.nodeLoaded) {
@@ -159,6 +164,20 @@ - (void)viewDidLayoutSubviews
     [_node recursivelyEnsureDisplaySynchronously:YES];
   }
   [super viewDidLayoutSubviews];
+
+  if (!AS_AT_LEAST_IOS11) {
+    [self _updateNodeFallbackSafeArea];
+  }
+}
+
+- (void)_updateNodeFallbackSafeArea
+{
+  UIEdgeInsets safeArea = UIEdgeInsetsMake(self.topLayoutGuide.length, 0, self.bottomLayoutGuide.length, 0);
+  UIEdgeInsets additionalInsets = self.additionalSafeAreaInsets;
+
+  safeArea = ASConcatInsets(safeArea, additionalInsets);
+
+  _node.fallbackSafeAreaInsets = safeArea;
 }
 
 ASVisibilityDidMoveToParentViewController;
@@ -264,6 +283,25 @@ - (ASInterfaceState)interfaceState
   return _node.interfaceState;
 }
 
+- (UIEdgeInsets)additionalSafeAreaInsets
+{
+  if (AS_AVAILABLE_IOS(11.0)) {
+    return super.additionalSafeAreaInsets;
+  }
+
+  return _fallbackAdditionalSafeAreaInsets;
+}
+
+- (void)setAdditionalSafeAreaInsets:(UIEdgeInsets)additionalSafeAreaInsets
+{
+  if (AS_AVAILABLE_IOS(11.0)) {
+    [super setAdditionalSafeAreaInsets:additionalSafeAreaInsets];
+  } else {
+    _fallbackAdditionalSafeAreaInsets = additionalSafeAreaInsets;
+    [self _updateNodeFallbackSafeArea];
+  }
+}
+
 #pragma mark - ASTraitEnvironment
 
 - (ASPrimitiveTraitCollection)primitiveTraitCollectionForUITraitCollection:(UITraitCollection *)traitCollection

Source/Details/UIView+ASConvenience.h

@@ -75,6 +75,9 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, assign, getter=isUserInteractionEnabled) BOOL userInteractionEnabled;
 @property (nonatomic, assign, getter=isExclusiveTouch) BOOL exclusiveTouch;
 @property (nonatomic, assign, getter=asyncdisplaykit_isAsyncTransactionContainer, setter = asyncdisplaykit_setAsyncTransactionContainer:) BOOL asyncdisplaykit_asyncTransactionContainer;
+@property (nonatomic, assign)           UIEdgeInsets layoutMargins;
+@property (nonatomic, assign)           BOOL preservesSuperviewLayoutMargins;
+@property (nonatomic, assign)           BOOL insetsLayoutMarginsFromSafeArea;
 
 /**
  Following properties of the UIAccessibility informal protocol are supported as well.

Source/Details/_ASDisplayView.mm

@@ -21,11 +21,13 @@
 #import <AsyncDisplayKit/_ASCoreAnimationExtras.h>
 #import <AsyncDisplayKit/_ASDisplayLayer.h>
 #import <AsyncDisplayKit/ASDisplayNodeInternal.h>
+#import <AsyncDisplayKit/ASDisplayNode+Convenience.h>
 #import <AsyncDisplayKit/ASDisplayNode+FrameworkPrivate.h>
 #import <AsyncDisplayKit/ASDisplayNode+Subclasses.h>
 #import <AsyncDisplayKit/ASInternalHelpers.h>
-#import <AsyncDisplayKit/ASObjectDescriptionHelpers.h>
 #import <AsyncDisplayKit/ASLayout.h>
+#import <AsyncDisplayKit/ASObjectDescriptionHelpers.h>
+#import <AsyncDisplayKit/ASViewController.h>
 
 #pragma mark - _ASDisplayViewMethodOverrides
 
@@ -234,6 +236,16 @@ - (void)didMoveToSuperview
     self.keepalive_node = nil;
   }
 
+#if DEBUG
+  // This is only to help detect issues when a root-of-view-controller node is reused separately from its view controller.
+  // Avoid overhead in release.
+  if (superview && node.viewControllerRoot) {
+    UIViewController *vc = [node closestViewController];
+
+    ASDisplayNodeAssert(vc != nil && [vc isKindOfClass:[ASViewController class]] && ((ASViewController*)vc).node == node, @"This node was once used as a view controller's node. You should not reuse it without its view controller.");
+  }
+#endif
+
   ASDisplayNode *supernode = node.supernode;
   ASDisplayNodeAssert(!supernode.isLayerBacked, @"Shouldn't be possible for superview's node to be layer-backed.");
 
@@ -481,6 +493,22 @@ - (BOOL)canPerformAction:(SEL)action withSender:(id)sender
   return ([super canPerformAction:action withSender:sender] || [node respondsToSelector:action]);
 }
 
+- (void)layoutMarginsDidChange
+{
+  ASDisplayNode *node = _asyncdisplaykit_node; // Create strong reference to weak ivar.
+  [super layoutMarginsDidChange];
+
+  [node layoutMarginsDidChange];
+}
+
+- (void)safeAreaInsetsDidChange
+{
+  ASDisplayNode *node = _asyncdisplaykit_node; // Create strong reference to weak ivar.
+  [super safeAreaInsetsDidChange];
+
+  [node safeAreaInsetsDidChange];
+}
+
 - (id)forwardingTargetForSelector:(SEL)aSelector
 {
   // Ideally, we would implement -targetForAction:withSender: and simply return the node where we don't respond personally.

Source/Private/ASDisplayNode+FrameworkPrivate.h

@@ -241,6 +241,25 @@ __unused static NSString * _Nonnull NSStringFromASHierarchyStateChange(ASHierarc
  */
 - (BOOL)shouldScheduleDisplayWithNewInterfaceState:(ASInterfaceState)newInterfaceState;
 
+/**
+ * @abstract safeAreaInsets will fallback to this value if the corresponding UIKit property is not available
+ * (due to an old iOS version).
+ *
+ * @discussion This should be set by the owning view controller based on it's layout guides.
+ * If this is not a view controllet's node the value will be calculated automatically by the parent node.
+ */
+@property (nonatomic, assign) UIEdgeInsets fallbackSafeAreaInsets;
+
+/**
+ * @abstract Indicates if this node is a view controller's root node. Defaults to NO.
+ *
+ * @discussion Set to YES in -[ASViewController initWithNode:].
+ *
+ * YES here only means that this node is used as an ASViewController node. It doesn't mean that this node is a root of
+ * ASDisplayNode hierarchy, e.g. when its view controller is parented by another ASViewController.
+ */
+@property (nonatomic, assign, getter=isViewControllerRoot) BOOL viewControllerRoot;
+
 @end