Addressed comments to LayoutOptions PR

AsyncDisplayKit/Layout/ASLayoutable.h

@@ -20,11 +20,22 @@
 @class ASLayoutSpec;
 
 /** 
- * The ASLayoutable protocol declares a method for measuring the layout of an object. A class must implement the method
- * so that instances of that class can be used to build layout trees. The protocol also provides information 
- * about how an object should be laid out within an ASStackLayoutSpec.
+ * The ASLayoutable protocol declares a method for measuring the layout of an object. A layout
+ * is defined by an ASLayout return value, and must specify 1) the size (but not position) of the
+ * layoutable object, and 2) the size and position of all of its immediate child objects. The tree 
+ * recursion is driven by parents requesting layouts from their children in order to determine their 
+ * size, followed by the parents setting the position of the children once the size is known
+ *
+ * The protocol also implements a "family" of Layoutable protocols. These protocols contain layout 
+ * options that can be used for specific layout specs. For example, ASStackLayoutSpec has options
+ * defining how a layoutable should shrink or grow based upon available space.
+ *
+ * These layout options are all stored in an ASLayoutOptions class (that is defined in ASLayoutablePrivate).
+ * Generally you needn't worry about the layout options class, as the layoutable protocols allow all direct
+ * access to the options via convenience properties. If you are creating custom layout spec, then you can
+ * extend the backing layout options class to accomodate any new layout options.
  */
-@protocol ASLayoutable <ASLayoutablePrivate, ASStackLayoutable, ASStaticLayoutable>
+@protocol ASLayoutable <ASStackLayoutable, ASStaticLayoutable, ASLayoutablePrivate>
 
 /**
  * @abstract Calculate a layout based on given size range.
@@ -35,4 +46,64 @@
  */
 - (ASLayout *)measureWithSizeRange:(ASSizeRange)constrainedSize;
 
+
+#pragma mark - Layout options from the Layoutable Protocols
+
+#pragma mark - ASStackLayoutable
+/**
+ * @abstract Additional space to place before this object in the stacking direction.
+ * Used when attached to a stack layout.
+ */
+@property (nonatomic, readwrite) CGFloat spacingBefore;
+
+/**
+ * @abstract Additional space to place after this object in the stacking direction.
+ * Used when attached to a stack layout.
+ */
+@property (nonatomic, readwrite) CGFloat spacingAfter;
+
+/**
+ * @abstract If the sum of childrens' stack dimensions is less than the minimum size, should this object grow?
+ * Used when attached to a stack layout.
+ */
+@property (nonatomic, readwrite) BOOL flexGrow;
+
+/**
+ * @abstract If the sum of childrens' stack dimensions is greater than the maximum size, should this object shrink?
+ * Used when attached to a stack layout.
+ */
+@property (nonatomic, readwrite) BOOL flexShrink;
+
+/**
+ * @abstract Specifies the initial size in the stack dimension for this object.
+ * Default to ASRelativeDimensionUnconstrained.
+ * Used when attached to a stack layout.
+ */
+@property (nonatomic, readwrite) ASRelativeDimension flexBasis;
+
+/**
+ * @abstract Orientation of the object along cross axis, overriding alignItems
+ * Used when attached to a stack layout.
+ */
+@property (nonatomic, readwrite) ASStackLayoutAlignSelf alignSelf;
+
+/**
+ *  @abstract Used for baseline alignment. The distance from the top of the object to its baseline.
+ */
+@property (nonatomic, readwrite) CGFloat ascender;
+
+/**
+ *  @abstract Used for baseline alignment. The distance from the baseline of the object to its bottom.
+ */
+@property (nonatomic, readwrite) CGFloat descender;
+
+#pragma mark - ASStaticLayoutable
+/**
+ If specified, the child's size is restricted according to this size. Percentages are resolved relative to the static layout spec.
+ */
+@property (nonatomic, assign) ASRelativeSizeRange sizeRange;
+
+/** The position of this object within its parent spec. */
+@property (nonatomic, assign) CGPoint layoutPosition;
+
 @end