Create a Pluggable "Tips" System to Help in Development

Source/ASCellNode.mm

@@ -368,6 +368,11 @@ - (NSString *)supplementaryElementKind
   return self.collectionElement.supplementaryElementKind;
 }
 
+- (BOOL)supportsLayerBacking
+{
+  return NO;
+}
+
 @end
 
 

Source/ASControlNode.mm

@@ -273,6 +273,11 @@ - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
   return YES;
 }
 
+- (BOOL)supportsLayerBacking
+{
+  return super.supportsLayerBacking && !self.userInteractionEnabled;
+}
+
 #pragma mark - Action Messages
 
 - (void)addTarget:(id)target action:(SEL)action forControlEvents:(ASControlNodeEvent)controlEventMask
@@ -424,7 +429,7 @@ - (void)sendActionsForControlEvents:(ASControlNodeEvent)controlEvents withEvent:
     (ASControlNodeEvent controlEvent)
     {
       // Use a copy to itereate, the action perform could call remove causing a mutation crash.
-      NSMutableArray *eventTargetActionArray = [_controlEventDispatchTable[_ASControlNodeEventKeyForControlEvent(controlEvent)] copy];
+      NSArray *eventTargetActionArray = [_controlEventDispatchTable[_ASControlNodeEventKeyForControlEvent(controlEvent)] copy];
 
       // Iterate on each target action pair
       for (ASControlTargetAction *targetAction in eventTargetActionArray) {

Source/ASDisplayNode.h

@@ -592,6 +592,11 @@ extern NSInteger const ASDefaultDrawingPriority;
  */
 - (CGRect)convertRect:(CGRect)rect fromNode:(nullable ASDisplayNode *)node AS_WARN_UNUSED_RESULT;
 
+/**
+ * Whether or not the node would support having .layerBacked = YES.
+ */
+@property (nonatomic, readonly) BOOL supportsLayerBacking;
+
 @end
 
 /**

Source/ASDisplayNode.mm

@@ -37,6 +37,7 @@
 #import <AsyncDisplayKit/ASTraitCollection.h>
 #import <AsyncDisplayKit/ASWeakProxy.h>
 #import <AsyncDisplayKit/ASResponderChainEnumerator.h>
+#import <AsyncDisplayKit/ASTipsController.h>
 
 #if ASDisplayNodeLoggingEnabled
   #define LOG(...) NSLog(__VA_ARGS__)
@@ -245,11 +246,6 @@ + (void)load
   ASScreenScale();
 }
 
-+ (BOOL)layerBackedNodesEnabled
-{
-  return YES;
-}
-
 + (Class)viewClass
 {
   return [_ASDisplayView class];
@@ -275,6 +271,8 @@ - (void)_initializeInstance
   _eventLog = [[ASEventLog alloc] initWithObject:self];
 #endif
 
+  _viewClass = [self.class viewClass];
+  _layerClass = [self.class layerClass];
   _contentsScaleForDisplay = ASScreenScale();
 
   _primitiveTraitCollection = ASPrimitiveTraitCollectionMakeDefault();
@@ -574,9 +572,6 @@ - (UIView *)_locked_viewToLoad
     _viewBlock = nil;
     _viewClass = [view class];
   } else {
-    if (!_viewClass) {
-      _viewClass = [self.class viewClass];
-    }
     view = [[_viewClass alloc] init];
   }
 
@@ -610,9 +605,6 @@ - (CALayer *)_locked_layerToLoad
     _layerBlock = nil;
     _layerClass = [layer class];
   } else {
-    if (!_layerClass) {
-      _layerClass = [self.class layerClass];
-    }
     layer = [[_layerClass alloc] init];
   }
 
@@ -805,26 +797,22 @@ - (BOOL)isSynchronous
   return _flags.synchronous;
 }
 
-- (void)setSynchronous:(BOOL)flag
-{
-  ASDN::MutexLocker l(__instanceLock__);
-  _flags.synchronous = flag;
-}
-
 - (void)setLayerBacked:(BOOL)isLayerBacked
 {
-  if (![self.class layerBackedNodesEnabled]) {
-    return;
-  }
+  // Only call this if assertions are enabled – it could be expensive.
+  ASDisplayNodeAssert(!isLayerBacked || self.supportsLayerBacking, @"Node %@ does not support layer backing.", self);
 
   ASDN::MutexLocker l(__instanceLock__);
-  ASDisplayNodeAssert(!_view && !_layer, @"Cannot change isLayerBacked after layer or view has loaded");
-  ASDisplayNodeAssert(!_viewBlock && !_layerBlock, @"Cannot change isLayerBacked when a layer or view block is provided");
-  ASDisplayNodeAssert(!_viewClass && !_layerClass, @"Cannot change isLayerBacked when a layer or view class is provided");
-
-  if (isLayerBacked != _flags.layerBacked && !_view && !_layer) {
-    _flags.layerBacked = isLayerBacked;
+  if (_flags.layerBacked == isLayerBacked) {
+    return;
   }
+
+  if ([self _locked_isNodeLoaded]) {
+    ASDisplayNodeFailAssert(@"Cannot change layerBacked after view/layer has loaded.");
+    return;
+  }
+
+  _flags.layerBacked = isLayerBacked;
 }
 
 - (BOOL)isLayerBacked
@@ -833,6 +821,12 @@ - (BOOL)isLayerBacked
   return _flags.layerBacked;
 }
 
+- (BOOL)supportsLayerBacking
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  return !_flags.synchronous && !_flags.viewEverHadAGestureRecognizerAttached && _viewClass == [_ASDisplayView class] && _layerClass == [_ASDisplayLayer class];
+}
+
 - (BOOL)shouldAnimateSizeChanges
 {
   ASDN::MutexLocker l(__instanceLock__);
@@ -857,6 +851,12 @@ - (void)setThreadSafeBounds:(CGRect)newBounds
   _threadSafeBounds = newBounds;
 }
 
+- (void)nodeViewDidAddGestureRecognizer
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  _flags.viewEverHadAGestureRecognizerAttached = YES;
+}
+
 #pragma mark - Layout
 
 #if DEBUG
@@ -3656,6 +3656,9 @@ - (void)didEnterVisibleState
   ASDisplayNodeAssertMainThread();
   ASDisplayNodeAssertLockUnownedByCurrentThread(__instanceLock__);
   [_interfaceStateDelegate didEnterVisibleState];
+#if AS_ENABLE_TIPS
+  [ASTipsController.shared nodeDidAppear:self];
+#endif
 }
 
 - (void)didExitVisibleState

Source/ASEditableTextNode.mm

@@ -306,6 +306,11 @@ - (void)setLayerBacked:(BOOL)layerBacked
   [super setLayerBacked:layerBacked];
 }
 
+- (BOOL)supportsLayerBacking
+{
+  return NO;
+}
+
 #pragma mark - Configuration
 @synthesize delegate = _delegate;
 

Source/ASMapNode.mm

@@ -427,5 +427,11 @@ - (void)layout
     }
   }
 }
+
+- (BOOL)supportsLayerBacking
+{
+  return NO;
+}
+
 @end
 #endif

Source/ASTextNode.mm

@@ -254,6 +254,28 @@ - (void)didLoad
   }
 }
 
+- (BOOL)supportsLayerBacking
+{
+  if (!super.supportsLayerBacking) {
+    return NO;
+  }
+
+  // If the text contains any links, return NO.
+  NSAttributedString *attributedText = self.attributedText;
+  NSRange range = NSMakeRange(0, attributedText.length);
+  for (NSString *linkAttributeName in _linkAttributeNames) {
+    __block BOOL hasLink = NO;
+    [attributedText enumerateAttribute:linkAttributeName inRange:range options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired usingBlock:^(id  _Nullable value, NSRange range, BOOL * _Nonnull stop) {
+      hasLink = (value != nil);
+      *stop = YES;
+    }];
+    if (hasLink) {
+      return NO;
+    }
+  }
+  return YES;
+}
+
 #pragma mark - Renderer Management
 
 - (ASTextKitRenderer *)_renderer

Source/ASVideoPlayerNode.mm

@@ -251,6 +251,11 @@ - (void)didEnterPreloadState
   }
 }
 
+- (BOOL)supportsLayerBacking
+{
+  return NO;
+}
+
 #pragma mark - UI
 
 - (void)createControls

Source/AsyncDisplayKit.h

@@ -115,6 +115,7 @@
 #import <AsyncDisplayKit/UIResponder+AsyncDisplayKit.h>
 
 #import <AsyncDisplayKit/AsyncDisplayKit+Debug.h>
+#import <AsyncDisplayKit/AsyncDisplayKit+Tips.h>
 #import <AsyncDisplayKit/ASDisplayNode+Deprecated.h>
 
 #import <AsyncDisplayKit/ASCollectionNode+Beta.h>

Source/Base/ASBaseDefines.h

@@ -104,6 +104,10 @@
 # define ASDISPLAYNODE_NOTHROW
 #endif
 
+#ifndef AS_ENABLE_TIPS
+#define AS_ENABLE_TIPS 0
+#endif
+
 /**
  * The event backtraces take a static 2KB of memory
  * and retain all objects present in all the registers

Source/Base/ASDisplayNode+Ancestry.h

@@ -0,0 +1,25 @@
+//
+//  ASNodeAncestorEnumerator.h
+//  AsyncDisplayKit
+//
+//  Created by Adlai Holler on 4/12/17.
+//  Copyright © 2017 Facebook. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+#import <AsyncDisplayKit/ASDisplayNode.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface ASDisplayNode (Ancestry)
+
+- (NSEnumerator *)ancestorEnumeratorWithSelf:(BOOL)includeSelf;
+
+/**
+ * e.g. "(<MYTextNode: 0xFFFF>, <MYTextContainingNode: 0xFFFF>, <MYCellNode: 0xFFFF>)"
+ */
+@property (atomic, copy, readonly) NSString *ancestryDescription;
+
+@end
+
+NS_ASSUME_NONNULL_END

Source/Base/ASDisplayNode+Ancestry.m

@@ -0,0 +1,55 @@
+//
+//  ASNodeAncestorEnumerator.m
+//  AsyncDisplayKit
+//
+//  Created by Adlai Holler on 4/12/17.
+//  Copyright © 2017 Facebook. All rights reserved.
+//
+
+#import "ASDisplayNode+Ancestry.h"
+
+AS_SUBCLASSING_RESTRICTED
+@interface ASNodeAncestryEnumerator : NSEnumerator
+@end
+
+@implementation ASNodeAncestryEnumerator {
+  /// Would be nice to use __unsafe_unretained but nodes can be
+  /// deallocated on arbitrary threads so nope.
+  __weak ASDisplayNode * _nextNode;
+}
+
+- (instancetype)initWithNode:(ASDisplayNode *)node
+{
+  if (self = [super init]) {
+    _nextNode = node;
+  }
+  return self;
+}
+
+- (id)nextObject
+{
+  ASDisplayNode *node = _nextNode;
+  _nextNode = [node supernode];
+  return node;
+}
+
+@end
+
+@implementation ASDisplayNode (Ancestry)
+
+- (NSEnumerator *)ancestorEnumeratorWithSelf:(BOOL)includeSelf
+{
+  ASDisplayNode *node = includeSelf ? self : self.supernode;
+  return [[ASNodeAncestryEnumerator alloc] initWithNode:node];
+}
+
+- (NSString *)ancestryDescription
+{
+  NSMutableArray *strings = [NSMutableArray array];
+  for (ASDisplayNode *node in [self ancestorEnumeratorWithSelf:YES]) {
+    [strings addObject:ASObjectDescriptionMakeTiny(node)];
+  }
+  return strings.description;
+}
+
+@end

Source/Debug/AsyncDisplayKit+Tips.h

@@ -0,0 +1,42 @@
+//
+//  AsyncDisplayKit+Tips.h
+//  AsyncDisplayKit
+//
+//  Created by Adlai Holler on 4/12/17.
+//  Copyright © 2017 Facebook. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+#import <AsyncDisplayKit/ASDisplayNode.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+typedef void(^ASTipDisplayBlock)(ASDisplayNode *node, NSString *message);
+
+/**
+ * The methods added to ASDisplayNode to control the tips system.
+ *
+ * To enable tips, define AS_ENABLE_TIPS=1 (e.g. modify ASBaseDefines.h).
+ */
+@interface ASDisplayNode (Tips)
+
+/**
+ * Whether this class should have tips active. Default YES.
+ *
+ * NOTE: This property is for _disabling_ tips on a per-class basis,
+ * if they become annoying or have false-positives. The tips system
+ * is completely disabled unless you define AS_ENABLE_TIPS=1.
+ */
+@property (class) BOOL enableTips;
+
+/**
+ * A block to be run on the main thread to show text when a tip is tapped.
+ *
+ * If nil, the default, the message is just logged to the console with the
+ * ancestry of the node.
+ */
+@property (class, nonatomic, copy, null_resettable) ASTipDisplayBlock tipDisplayBlock; 
+
+@end
+
+NS_ASSUME_NONNULL_END