[ASScrollNode] Add .scrollDirection property so that internal content sizing can be easily "unlimited" in the direction of scrolling. (#3001)

AsyncDisplayKit/ASScrollNode.h

@@ -9,6 +9,7 @@
 //
 
 #import <AsyncDisplayKit/ASDisplayNode.h>
+#import <AsyncDisplayKit/ASScrollDirection.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -33,6 +34,18 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property (nonatomic, assign) BOOL automaticallyManagesContentSize;
 
+/**
+ * @abstract This property controls how the constrainedSize is interpreted when sizing the content.
+ * if you are using automaticallyManagesContentSize, it can be crucial to ensure that the sizing is
+ * done how you expect.
+ * Vertical: The constrainedSize is interpreted as having unbounded .height (CGFLOAT_MAX), allowing
+ * stacks and other content in the layout spec to expand and result in scrollable content.
+ * Horizontal: The constrainedSize is interpreted as having unbounded .width (CGFLOAT_MAX), ...
+ * Vertical & Horizontal: the constrainedSize is interpreted as unbounded in both directions.
+ * @default ASScrollDirectionVerticalDirections
+ */
+@property (nonatomic, assign) ASScrollDirection scrollableDirections;
+
 @end
 
 NS_ASSUME_NONNULL_END

AsyncDisplayKit/ASScrollNode.mm

@@ -56,6 +56,7 @@
 
 @implementation ASScrollNode
 {
+  ASScrollDirection _scrollableDirections;
   BOOL _automaticallyManagesContentSize;
   CGSize _contentCalculatedSizeFromLayout;
 }
@@ -70,12 +71,20 @@
                      restrictedToSize:(ASLayoutElementSize)size
                  relativeToParentSize:(CGSize)parentSize
 {
-  ASLayout *layout = [super calculateLayoutThatFits:constrainedSize
+  ASDN::MutexLocker l(__instanceLock__);  // Lock for using our instance variables.
+
+  ASSizeRange contentConstrainedSize = constrainedSize;
+  if (ASScrollDirectionContainsVerticalDirection(_scrollableDirections)) {
+    contentConstrainedSize.max.height = CGFLOAT_MAX;
+  }
+  if (ASScrollDirectionContainsHorizontalDirection(_scrollableDirections)) {
+    contentConstrainedSize.max.width = CGFLOAT_MAX;
+  }
+  
+  ASLayout *layout = [super calculateLayoutThatFits:contentConstrainedSize
                                    restrictedToSize:size
                                relativeToParentSize:parentSize];
 
-  ASDN::MutexLocker l(__instanceLock__);  // Lock for using our two instance variables.
-  
   if (_automaticallyManagesContentSize) {
     // To understand this code, imagine we're containing a horizontal stack set within a vertical table node.
     // Our parentSize is fixed ~375pt width, but 0 - INF height.  Our stack measures 1000pt width, 50pt height.
@@ -124,6 +133,25 @@
 {
   ASDN::MutexLocker l(__instanceLock__);
   _automaticallyManagesContentSize = automaticallyManagesContentSize;
+  if (_automaticallyManagesContentSize == YES
+      && ASScrollDirectionContainsVerticalDirection(_scrollableDirections) == NO
+      && ASScrollDirectionContainsHorizontalDirection(_scrollableDirections) == NO) {
+    // Set the @default value, for more user-friendly behavior of the most
+    // common use cases of .automaticallyManagesContentSize.
+    _scrollableDirections = ASScrollDirectionVerticalDirections;
+  }
+}
+
+- (ASScrollDirection)scrollableDirections
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  return _scrollableDirections;
+}
+
+- (void)setScrollableDirections:(ASScrollDirection)scrollableDirections
+{
+  ASDN::MutexLocker l(__instanceLock__);
+  _scrollableDirections = scrollableDirections;
 }
 
 @end