Set background color directly to view or layer depending on if the node

is layerBacked.

Summary:
UIColor can now be a dynamic color provider to support capabilities like Dark Mode in applications. UIKit is able to re-render views when a user enters dark mode but this dynamic capabilities is not handled at the layer level.

Currently this takes the recommendation in facebookarchive/AsyncDisplayKit#1537 (comment) to set background color on the view directly or layer depending on if the node is layer backed. This change allows UIKit to track these colors and update the UI when the UITraitCollection.userInterfaceStyle changes.

Source/Private/ASDisplayNode+UIViewBridge.mm

@@ -511,7 +511,7 @@ - (void)layoutIfNeeded
 - (BOOL)isOpaque
 {
   _bridge_prologue_read;
-  return _getFromLayer(opaque);
+  return _getFromViewOrLayer(opaque, opaque);
 }
 
 - (void)setOpaque:(BOOL)newOpaque
@@ -740,13 +740,12 @@ - (void)setBackgroundColor:(UIColor *)newBackgroundColor
   if (shouldApply) {
     CGColorRef oldBackgroundCGColor = _layer.backgroundColor;
 
-    BOOL specialPropertiesHandling = ASDisplayNodeNeedsSpecialPropertiesHandling(checkFlag(Synchronous), _flags.layerBacked);
-    if (specialPropertiesHandling) {
-        _view.backgroundColor = newBackgroundColor;
+    if (_flags.layerBacked) {
+      _layer.backgroundColor = newBackgroundCGColor;
     } else {
-        _layer.backgroundColor = newBackgroundCGColor;
+      _view.backgroundColor = newBackgroundColor;
     }
-      
+
     if (!CGColorEqualToColor(oldBackgroundCGColor, newBackgroundCGColor)) {
       [self setNeedsDisplay];
     }

Source/Private/_ASPendingState.mm

@@ -1095,13 +1095,7 @@ - (void)applyToView:(UIView *)view withSpecialPropertiesHandling:(BOOL)specialPr
     view.clipsToBounds = _flags.clipsToBounds;
 
   if (flags.setBackgroundColor) {
-    // We have to make sure certain nodes get the background color call directly set
-    if (specialPropertiesHandling) {
-      view.backgroundColor = [UIColor colorWithCGColor:backgroundColor];
-    } else {
-      // Set the background color to the layer as in the UIView bridge we use this value as background color
-      layer.backgroundColor = backgroundColor;
-    }
+    view.backgroundColor = [UIColor colorWithCGColor:backgroundColor];
   }
 
   if (flags.setTintColor)

Tests/ASDisplayNodeTests.mm

@@ -1924,16 +1924,11 @@ - (void)checkBackgroundColorOpaqueRelationshipWithViewLoaded:(BOOL)loaded layerB
   XCTAssertTrue(node.opaque, @"Node should start opaque");
   XCTAssertTrue(node.layer.opaque, @"Node should start opaque");
 
-  node.backgroundColor = [UIColor clearColor];
+  node.backgroundColor = [UIColor blackColor];
 
   // This could be debated, but at the moment we differ from UIView's behavior to change the other property in response
   XCTAssertTrue(node.opaque, @"Set background color should not have made this not opaque");
   XCTAssertTrue(node.layer.opaque, @"Set background color should not have made this not opaque");
-
-  [node layer];
-
-  XCTAssertTrue(node.opaque, @"Set background color should not have made this not opaque");
-  XCTAssertTrue(node.layer.opaque, @"Set background color should not have made this not opaque");
 }
 
 - (void)testBackgroundColorOpaqueRelationshipView