[ASTextNode, ASDisplayNode] Create -calculatedLayoutDidChange and use it in text node.

This allows the change in size for the NSTextContainer to occur off the main thread, whenever that size change
is necessary.  Then the text relayout can occur earlier, during the process of computing ASLayoutSpecs.

Author: Scott Goodson

AsyncDisplayKit/ASDisplayNode+Subclasses.h

@@ -91,6 +91,13 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)layoutDidFinish;
 
+/**
+ * @abstract Called on a background thread if !isNodeLoaded - called on the main thread if isNodeLoaded.
+ *
+ * @discussion When the .calculatedLayout property is set to a new ASLayout (directly from -calculateLayoutThatFits: or
+ * calculated via use of -layoutSpecThatFits:), subclasses may inspect it here.
+ */
+- (void)calculatedLayoutDidChange;
 
 /** @name Layout calculation */
 

AsyncDisplayKit/ASDisplayNode.mm

@@ -594,6 +594,7 @@ - (ASLayout *)__measureWithSizeRange:(ASSizeRange)constrainedSize
     _layout = [self calculateLayoutThatFits:constrainedSize];
     _constrainedSize = constrainedSize;
     _flags.isMeasured = YES;
+    [self calculatedLayoutDidChange];
   }
 
   ASDisplayNodeAssertTrue(_layout.layoutableObject == self);
@@ -615,6 +616,10 @@ - (ASLayout *)__measureWithSizeRange:(ASSizeRange)constrainedSize
   return _layout;
 }
 
+- (void)calculatedLayoutDidChange
+{
+}
+
 - (BOOL)displaysAsynchronously
 {
   ASDN::MutexLocker l(_propertyLock);

AsyncDisplayKit/ASTextNode.mm

@@ -185,19 +185,6 @@ - (NSString *)description
 
 #pragma mark - ASDisplayNode
 
-- (CGSize)calculateSizeThatFits:(CGSize)constrainedSize
-{
-  ASDisplayNodeAssert(constrainedSize.width >= 0, @"Constrained width for text (%f) is too  narrow", constrainedSize.width);
-  ASDisplayNodeAssert(constrainedSize.height >= 0, @"Constrained height for text (%f) is too short", constrainedSize.height);
-
-  _constrainedSize = constrainedSize;
-  [self _invalidateRenderer];
-  ASDisplayNodeRespectThreadAffinityOfNode(self, ^{
-    [self setNeedsDisplay];
-  });
-  return [[self _renderer] size];
-}
-
 // FIXME: Re-evaluate if it is still the right decision to clear the renderer at this stage.
 // This code was written before TextKit and when 512MB devices were still the overwhelming majority.
 - (void)displayDidFinish
@@ -303,6 +290,8 @@ - (void)_invalidateRendererIfNeededForBoundsSize:(CGSize)boundsSize
   }
 }
 
+#pragma mark - Layout and Sizing
+
 - (BOOL)_needInvalidateRendererForBoundsSize:(CGSize)boundsSize
 {
   if (!_renderer) {
@@ -323,7 +312,7 @@ - (BOOL)_needInvalidateRendererForBoundsSize:(CGSize)boundsSize
     // as this would essentially serve to set its constrainedSize to be its calculatedSize (unnecessary).
     ASLayout *layout = self.calculatedLayout;
     if (layout != nil && CGSizeEqualToSize(boundsSize, layout.size)) {
-      if (!CGSizeEqualToSize(boundsSize, rendererConstrainedSize)) {
+      if (boundsSize.width != rendererConstrainedSize.width) {
         // Don't bother changing _constrainedSize, as ASDisplayNode's -measure: method would have a cache miss
         // and ask us to recalculate layout if it were called with the same calculatedSize that got us to this point!
         _renderer.constrainedSize = boundsSize;
@@ -335,6 +324,32 @@ - (BOOL)_needInvalidateRendererForBoundsSize:(CGSize)boundsSize
   }
 }
 
+- (void)calculatedLayoutDidChange
+{
+  ASLayout *layout = self.calculatedLayout;
+  if (layout != nil) {
+    _renderer.constrainedSize = layout.size;
+  }
+}
+
+- (CGSize)calculateSizeThatFits:(CGSize)constrainedSize
+{
+  ASDisplayNodeAssert(constrainedSize.width >= 0, @"Constrained width for text (%f) is too  narrow", constrainedSize.width);
+  ASDisplayNodeAssert(constrainedSize.height >= 0, @"Constrained height for text (%f) is too short", constrainedSize.height);
+  
+  _constrainedSize = constrainedSize;
+  
+  // Instead of invalidating the renderer, in case this is a new call with a different constrained size,
+  // just update the size of the NSTextContainer that is owned by the renderer's internal context object.
+  [self _renderer].constrainedSize = _constrainedSize;
+  
+  ASDisplayNodeRespectThreadAffinityOfNode(self, ^{
+    [self setNeedsDisplay];
+  });
+  
+  return [[self _renderer] size];
+}
+
 #pragma mark - Modifying User Text
 
 - (void)setAttributedString:(NSAttributedString *)attributedString