[ASControlNode] Upgrades to +setEnableHitTestDebug: to intersect hitTestSlop with parents' bounds+slop, to accurately predict and visualize UIKit event delivery edge cases.

Author: appleguy

AsyncDisplayKit/ASControlNode.mm

@@ -9,6 +9,8 @@
 #import "ASControlNode.h"
 #import "ASControlNode+Subclasses.h"
 #import "ASThread.h"
+#import "ASDisplayNodeExtras.h"
+#import "ASImageNode.h"
 
 // UIControl allows dragging some distance outside of the control itself during
 // tracking. This value depends on the device idiom (25 or 70 points), so
@@ -73,7 +75,7 @@ @interface ASControlNode ()
 
 @implementation ASControlNode
 {
-  ASDisplayNode *_debugHighlightOverlay;
+  ASImageNode *_debugHighlightOverlay;
 }
 
 #pragma mark - Lifecycle
@@ -251,10 +253,10 @@ - (void)addTarget:(id)target action:(SEL)action forControlEvents:(ASControlNodeE
 
       // add a highlight overlay node with area of ASControlNode + UIEdgeInsets
       self.clipsToBounds = NO;
-      _debugHighlightOverlay = [[ASDisplayNode alloc] init];
+      _debugHighlightOverlay = [[ASImageNode alloc] init];
+      _debugHighlightOverlay.zPosition = 1000;  // CALayer doesn't have -moveSublayerToFront, but this will ensure we're over the top of any siblings.
       _debugHighlightOverlay.layerBacked = YES;
-      _debugHighlightOverlay.backgroundColor = [[UIColor greenColor] colorWithAlphaComponent:0.5];
-      
+      _debugHighlightOverlay.backgroundColor = [[UIColor greenColor] colorWithAlphaComponent:0.4];
       [self addSubnode:_debugHighlightOverlay];
     }
   }
@@ -461,12 +463,35 @@ - (void)layout
   [super layout];
 
   if (_debugHighlightOverlay) {
-    UIEdgeInsets insets = [self hitTestSlop];
-    CGRect controlNodeRect = self.bounds;
-    _debugHighlightOverlay.frame = CGRectMake(controlNodeRect.origin.x + insets.left,
-                                              controlNodeRect.origin.y + insets.top,
-                                              controlNodeRect.size.width - insets.left - insets.right,
-                                              controlNodeRect.size.height - insets.top - insets.bottom);
+    
+    // Even if our parents don't have clipsToBounds set and would allow us to display the debug overlay, UIKit event delivery (hitTest:)
+    // will not search sub-hierarchies if one of our parents does not return YES for pointInside:.  In such a scenario, hitTestSlop
+    // may not be able to expand the tap target as much as desired without also setting some hitTestSlop on the limiting parents.
+    CGRect intersectRect = UIEdgeInsetsInsetRect(self.bounds, [self hitTestSlop]);
+    CALayer *layer = self.layer;
+    CALayer *intersectLayer = layer;
+    CALayer *intersectSuperlayer = layer.superlayer;
+    
+    // Stop climbing if we encounter a UIScrollView, as its offset bounds origin may make it seem like our events will be clipped when
+    // scrolling will actually reveal them (because this process will not re-run due to scrolling)
+    while (intersectSuperlayer && ![intersectSuperlayer.delegate respondsToSelector:@selector(contentOffset)]) {
+      // Get our parent's tappable bounds.  If the parent has an associated node, consider hitTestSlop, as it will extend its pointInside:.
+      CGRect parentHitRect = intersectSuperlayer.bounds;
+      ASDisplayNode *parentNode = ASLayerToDisplayNode(intersectSuperlayer);
+      if (parentNode) {
+        parentHitRect = UIEdgeInsetsInsetRect(parentHitRect, [parentNode hitTestSlop]);
+      }
+      
+      // Convert our current rectangle to parent coordinates, and intersect with the parent's hit rect.
+      CGRect intersectRectInParentCoordinates = [intersectSuperlayer convertRect:intersectRect fromLayer:intersectLayer];
+      intersectRect = CGRectIntersection(parentHitRect, intersectRectInParentCoordinates);
+
+      // Advance up the tree.
+      intersectLayer = intersectSuperlayer;
+      intersectSuperlayer = intersectLayer.superlayer;
+    }
+    
+    _debugHighlightOverlay.frame = [intersectLayer convertRect:intersectRect toLayer:layer];
   }
 }
 

AsyncDisplayKit/ASDisplayNode.mm

@@ -2383,11 +2383,13 @@ - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
   return [superview gestureRecognizerShouldBegin:gestureRecognizer];
 }
 
+#if DEBUG
 - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
 {
   ASDisplayNodeAssertMainThread();
   return [_view hitTest:point withEvent:event];
 }
+#endif
 
 - (void)setHitTestSlop:(UIEdgeInsets)hitTestSlop
 {

AsyncDisplayKit/ASImageNode.mm

@@ -100,12 +100,6 @@ - (id)init
   _cropDisplayBounds = CGRectNull;
   _placeholderColor = ASDisplayNodeDefaultPlaceholderColor();
 
-  if ([ASImageNode shouldShowImageScalingOverlay]) {
-    _debugLabelNode = [[ASTextNode alloc] init];
-    _debugLabelNode.layerBacked = YES;
-    [self addSubnode:_debugLabelNode];
-  }
-
   return self;
 }
 
@@ -144,6 +138,14 @@ - (void)setImage:(UIImage *)image
     [self invalidateCalculatedLayout];
     if (image) {
       [self setNeedsDisplay];
+      
+      if ([ASImageNode shouldShowImageScalingOverlay]) {
+        ASPerformBlockOnMainThread(^{
+          _debugLabelNode = [[ASTextNode alloc] init];
+          _debugLabelNode.layerBacked = YES;
+          [self addSubnode:_debugLabelNode];
+        });
+      }
     } else {
       self.contents = nil;
     }