From eebdaffab4405e1d56f8f138cfd30e6d475a4129 Mon Sep 17 00:00:00 2001
From: Nelson Tai <chiahsien@gmail.com>
Date: Wed, 5 Feb 2014 00:03:06 +0800
Subject: [PATCH 1/6] [Fix] shouldInvalidateLayoutForBoundsChange

---
 CHTCollectionViewWaterfallLayout.m | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/CHTCollectionViewWaterfallLayout.m b/CHTCollectionViewWaterfallLayout.m
index be1813e..71a489c 100644
--- a/CHTCollectionViewWaterfallLayout.m
+++ b/CHTCollectionViewWaterfallLayout.m
@@ -267,6 +267,11 @@ - (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
 }
 
 - (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
+  CGRect oldBounds = self.collectionView.bounds;
+  if (CGRectGetWidth(newBounds) != CGRectGetWidth(oldBounds) ||
+      CGRectGetHeight(newBounds) != CGRectGetHeight(oldBounds)) {
+    return YES;
+  }
   return NO;
 }
 

From 36202fc669a15e04b4143ad76ea7174613d1663e Mon Sep 17 00:00:00 2001
From: Andreas Maechler <andreas.maechler@varian.com>
Date: Thu, 6 Feb 2014 10:26:16 -0800
Subject: [PATCH 2/6] Call [self commonInit] also in initWithCoder:

When using Nibs / storyboards for initializing the layout, initWithCoder
is the designated initializer.
---
 CHTCollectionViewWaterfallLayout.m | 36 ++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/CHTCollectionViewWaterfallLayout.m b/CHTCollectionViewWaterfallLayout.m
index be1813e..8aa6569 100644
--- a/CHTCollectionViewWaterfallLayout.m
+++ b/CHTCollectionViewWaterfallLayout.m
@@ -81,20 +81,32 @@ - (void)setVerticalItemSpacing:(CGFloat)verticalItemSpacing {
 }
 
 #pragma mark - Init
-- (void)commonInit {
-  _columnCount = 2;
-  _itemWidth = 140;
-  _headerHeight = 0;
-  _footerHeight = 0;
-  _verticalItemSpacing = 0;
-  _sectionInset = UIEdgeInsetsZero;
-}
 
 - (id)init {
-  if (self = [super init]) {
-    [self commonInit];
-  }
-  return self;
+    self = [super init];
+    if (self) {
+        [self commonInit];
+    }
+    
+    return self;
+}
+
+- (id)initWithCoder:(NSCoder *)aDecoder {
+    self = [super init];
+    if (self) {
+        [self commonInit];
+    }
+    
+    return self;
+}
+
+- (void)commonInit {
+    _columnCount = 2;
+    _itemWidth = 140;
+    _headerHeight = 0;
+    _footerHeight = 0;
+    _verticalItemSpacing = 0;
+    _sectionInset = UIEdgeInsetsZero;
 }
 
 #pragma mark - Methods to Override

From c6544f4f871c8512810be6b54fc434fd1f172cf2 Mon Sep 17 00:00:00 2001
From: Nelson Tai <chiahsien@gmail.com>
Date: Sun, 9 Feb 2014 00:54:55 +0800
Subject: [PATCH 3/6] Section header and/or footer should work properly

---
 CHTCollectionViewWaterfallLayout.h |  18 ++--
 CHTCollectionViewWaterfallLayout.m | 160 +++++++++++++++++++++--------
 2 files changed, 126 insertions(+), 52 deletions(-)

diff --git a/CHTCollectionViewWaterfallLayout.h b/CHTCollectionViewWaterfallLayout.h
index a4d08b0..9e9167b 100644
--- a/CHTCollectionViewWaterfallLayout.h
+++ b/CHTCollectionViewWaterfallLayout.h
@@ -7,9 +7,13 @@
 
 #import <UIKit/UIKit.h>
 
-#pragma mark - Constants
+/**
+ *  Constants that specify the types of supplementary views that can be presented using a waterfall layout.
+ */
 
+/// A supplementary view that identifies the header for a given section.
 extern NSString *const CHTCollectionElementKindSectionHeader;
+/// A supplementary view that identifies the footer for a given section.
 extern NSString *const CHTCollectionElementKindSectionFooter;
 
 #pragma mark - CHTCollectionViewDelegateWaterfallLayout
@@ -31,9 +35,7 @@ extern NSString *const CHTCollectionElementKindSectionFooter;
  *  @return
  *    The height of the specified item. Must be greater than 0.
  */
-- (CGFloat)collectionView:(UICollectionView *)collectionView
-                   layout:(UICollectionViewLayout *)collectionViewLayout
- heightForItemAtIndexPath:(NSIndexPath *)indexPath;
+- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout heightForItemAtIndexPath:(NSIndexPath *)indexPath;
 
 @optional
 /**
@@ -55,9 +57,7 @@ extern NSString *const CHTCollectionElementKindSectionFooter;
  *  @see
  *    headerHeight
  */
-- (CGFloat)collectionView:(UICollectionView *)collectionView
-                   layout:(UICollectionViewLayout *)collectionViewLayout
- heightForHeaderInSection:(NSInteger)section;
+- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout heightForHeaderInSection:(NSInteger)section;
 
 /**
  *  Asks the delegate for the height of the footer view in the specified section.
@@ -78,9 +78,7 @@ extern NSString *const CHTCollectionElementKindSectionFooter;
  *  @see
  *    footerHeight
  */
-- (CGFloat)collectionView:(UICollectionView *)collectionView
-                   layout:(UICollectionViewLayout *)collectionViewLayout
- heightForFooterInSection:(NSInteger)section;
+- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout heightForFooterInSection:(NSInteger)section;
 @end
 
 #pragma mark - CHTCollectionViewWaterfallLayout
diff --git a/CHTCollectionViewWaterfallLayout.m b/CHTCollectionViewWaterfallLayout.m
index 71a489c..56f2a3d 100644
--- a/CHTCollectionViewWaterfallLayout.m
+++ b/CHTCollectionViewWaterfallLayout.m
@@ -11,19 +11,18 @@
 NSString *const CHTCollectionElementKindSectionFooter = @"CHTCollectionElementKindSectionFooter";
 
 @interface CHTCollectionViewWaterfallLayout ()
-@property (nonatomic, weak) id<CHTCollectionViewDelegateWaterfallLayout> delegate;
+/// The delegate will point to collectionView.delegate automatically.
+@property (nonatomic, weak) id <CHTCollectionViewDelegateWaterfallLayout> delegate;
 /// Array to store height for each column
 @property (nonatomic, strong) NSMutableArray *columnHeights;
-/// Array of arrays
-/// Each array stores item attributes for each section
+/// Array of arrays. Each array stores item attributes for each section
 @property (nonatomic, strong) NSMutableArray *sectionItemAttributes;
-/// Array to store attributes for all items
-/// Include headers, cells, and footers
+/// Array to store attributes for all items includes headers, cells, and footers
 @property (nonatomic, strong) NSMutableArray *allItemAttributes;
-/// Array to store attributes for headers
-@property (nonatomic, strong) NSMutableArray *headersAttributes;
-/// Array to store attributes for footers
-@property (nonatomic, strong) NSMutableArray *footersAttributes;
+/// Dictionary to store section headers' attribute
+@property (nonatomic, strong) NSMutableDictionary *headersAttribute;
+/// Dictionary to store section footers' attribute
+@property (nonatomic, strong) NSMutableDictionary *footersAttrubite;
 /// Array to store union rectangles
 @property (nonatomic, strong) NSMutableArray *unionRects;
 /// Inter spacing at X-axis for each item
@@ -80,6 +79,48 @@ - (void)setVerticalItemSpacing:(CGFloat)verticalItemSpacing {
   }
 }
 
+- (NSMutableDictionary *)headersAttribute {
+  if (!_headersAttribute) {
+    _headersAttribute = [NSMutableDictionary dictionary];
+  }
+  return _headersAttribute;
+}
+
+- (NSMutableDictionary *)footersAttrubite {
+  if (!_footersAttrubite) {
+    _footersAttrubite = [NSMutableDictionary dictionary];
+  }
+  return _footersAttrubite;
+}
+
+- (NSMutableArray *)unionRects {
+  if (!_unionRects) {
+    _unionRects = [NSMutableArray array];
+  }
+  return _unionRects;
+}
+
+- (NSMutableArray *)columnHeights {
+  if (!_columnHeights) {
+    _columnHeights = [NSMutableArray array];
+  }
+  return _columnHeights;
+}
+
+- (NSMutableArray *)allItemAttributes {
+  if (!_allItemAttributes) {
+    _allItemAttributes = [NSMutableArray array];
+  }
+  return _allItemAttributes;
+}
+
+- (NSMutableArray *)sectionItemAttributes {
+  if (!_sectionItemAttributes) {
+    _sectionItemAttributes = [NSMutableArray array];
+  }
+  return _sectionItemAttributes;
+}
+
 #pragma mark - Init
 - (void)commonInit {
   _columnCount = 2;
@@ -88,6 +129,7 @@ - (void)commonInit {
   _footerHeight = 0;
   _verticalItemSpacing = 0;
   _sectionInset = UIEdgeInsetsZero;
+  _delegate = (id <CHTCollectionViewDelegateWaterfallLayout> )self.collectionView.delegate;
 }
 
 - (id)init {
@@ -123,13 +165,12 @@ - (void)prepareLayout {
     self.interItemSpacingY = self.interItemSpacingX;
   }
 
-  self.delegate = (id<CHTCollectionViewDelegateWaterfallLayout>)self.collectionView.delegate;
-  self.headersAttributes = [NSMutableArray array];
-  self.footersAttributes = [NSMutableArray array];
-  self.unionRects = [NSMutableArray array];
-  self.columnHeights = [NSMutableArray array];
-  self.allItemAttributes = [NSMutableArray array];
-  self.sectionItemAttributes = [NSMutableArray array];
+  [self.headersAttribute removeAllObjects];
+  [self.footersAttrubite removeAllObjects];
+  [self.unionRects removeAllObjects];
+  [self.columnHeights removeAllObjects];
+  [self.allItemAttributes removeAllObjects];
+  [self.sectionItemAttributes removeAllObjects];
 
   for (idx = 0; idx < self.columnCount; idx++) {
     [self.columnHeights addObject:@(0)];
@@ -138,26 +179,40 @@ - (void)prepareLayout {
   // Create attributes
   CGFloat sectionTop = self.sectionInset.top;
   UICollectionViewLayoutAttributes *attributes;
-  for (NSInteger section = 0; section < numberOfSections; ++section) {
-    // 1. Section header
-    attributes = [UICollectionViewLayoutAttributes layoutAttributesForSupplementaryViewOfKind:CHTCollectionElementKindSectionHeader withIndexPath:[NSIndexPath indexPathForItem:0 inSection:section]];
 
+  for (NSInteger section = 0; section < numberOfSections; ++section) {
+    /*
+     * 1. Section header
+     */
+    CGFloat headerHeight;
     if ([self.delegate respondsToSelector:@selector(collectionView:layout:heightForHeaderInSection:)]) {
-      CGFloat headerHeight = [self.delegate collectionView:self.collectionView layout:self heightForHeaderInSection:section];
-      attributes.frame = CGRectMake(self.sectionInset.left, sectionTop, width, headerHeight);
+      headerHeight = [self.delegate collectionView:self.collectionView layout:self heightForHeaderInSection:section];
     } else {
-      attributes.frame = CGRectMake(self.sectionInset.left, sectionTop, width, self.headerHeight);
+      headerHeight = self.headerHeight;
     }
-    [self.headersAttributes addObject:attributes];
-    [self.allItemAttributes addObject:attributes];
 
-    for (idx = 0; idx < self.columnCount; idx++) {
-      self.columnHeights[idx] = @(CGRectGetMaxY(attributes.frame) + self.interItemSpacingY);
+    if (headerHeight > 0) {
+      attributes = [UICollectionViewLayoutAttributes layoutAttributesForSupplementaryViewOfKind:CHTCollectionElementKindSectionHeader withIndexPath:[NSIndexPath indexPathForItem:0 inSection:section]];
+      attributes.frame = CGRectMake(self.sectionInset.left, sectionTop, width, headerHeight);
+
+      self.headersAttribute[@(section)] = attributes;
+      [self.allItemAttributes addObject:attributes];
+
+      for (idx = 0; idx < self.columnCount; idx++) {
+        self.columnHeights[idx] = @(CGRectGetMaxY(attributes.frame) + self.interItemSpacingY);
+      }
+    } else {
+      for (idx = 0; idx < self.columnCount; idx++) {
+        self.columnHeights[idx] = @(sectionTop);
+      }
     }
 
-    // 2. Section items
+    /*
+     * 2. Section items
+     */
     NSInteger itemCount = [self.collectionView numberOfItemsInSection:section];
     NSMutableArray *itemAttributes = [NSMutableArray arrayWithCapacity:itemCount];
+
     // Item will be put into shortest column.
     for (idx = 0; idx < itemCount; idx++) {
       NSIndexPath *indexPath = [NSIndexPath indexPathForItem:idx inSection:section];
@@ -175,23 +230,35 @@ - (void)prepareLayout {
 
     [self.sectionItemAttributes addObject:itemAttributes];
 
-    // 3. Section footer
+    /*
+     * Section footer
+     */
     NSUInteger columnIndex = [self longestColumnIndex];
     CGFloat yOffset = [self.columnHeights[columnIndex] floatValue];
-    attributes = [UICollectionViewLayoutAttributes layoutAttributesForSupplementaryViewOfKind:CHTCollectionElementKindSectionFooter withIndexPath:[NSIndexPath indexPathForItem:0 inSection:section]];
+    CGFloat footerHeight;
 
     if ([self.delegate respondsToSelector:@selector(collectionView:layout:heightForFooterInSection:)]) {
-      CGFloat footerHeight = [self.delegate collectionView:self.collectionView layout:self heightForFooterInSection:section];
-      attributes.frame = CGRectMake(self.sectionInset.left, yOffset, width, footerHeight);
+      footerHeight = [self.delegate collectionView:self.collectionView layout:self heightForFooterInSection:section];
     } else {
-      attributes.frame = CGRectMake(self.sectionInset.left, yOffset, width, self.footerHeight);
+      footerHeight = self.footerHeight;
     }
-    [self.footersAttributes addObject:attributes];
-    [self.allItemAttributes addObject:attributes];
+    
+    if (footerHeight > 0) {
+      attributes = [UICollectionViewLayoutAttributes layoutAttributesForSupplementaryViewOfKind:CHTCollectionElementKindSectionFooter withIndexPath:[NSIndexPath indexPathForItem:0 inSection:section]];
+      attributes.frame = CGRectMake(self.sectionInset.left, yOffset, width, footerHeight);
+
+      self.footersAttrubite[@(section)] = attributes;
+      [self.allItemAttributes addObject:attributes];
 
-    sectionTop = CGRectGetMaxY(attributes.frame) + self.interItemSpacingY;
-    for (idx = 0; idx < self.columnCount; idx++) {
-      self.columnHeights[idx] = @(sectionTop);
+      sectionTop = CGRectGetMaxY(attributes.frame) + self.interItemSpacingY;
+      for (idx = 0; idx < self.columnCount; idx++) {
+        self.columnHeights[idx] = @(sectionTop);
+      }
+    } else {
+      sectionTop = yOffset + self.interItemSpacingY;
+      for (idx = 0; idx < self.columnCount; idx++) {
+        self.columnHeights[idx] = @(sectionTop);
+      }
     }
   } // end of for (NSInteger section = 0; section < numberOfSections; ++section)
 
@@ -231,12 +298,13 @@ - (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSInde
 }
 
 - (UICollectionViewLayoutAttributes *)layoutAttributesForSupplementaryViewOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
+  UICollectionViewLayoutAttributes *attribute = nil;
   if ([kind isEqualToString:CHTCollectionElementKindSectionHeader]) {
-    return self.headersAttributes[indexPath.section];
+    attribute = self.headersAttribute[@(indexPath.section)];
   } else if ([kind isEqualToString:CHTCollectionElementKindSectionFooter]) {
-    return self.footersAttributes[indexPath.section];
+    attribute = self.footersAttrubite[@(indexPath.section)];
   }
-  return nil;
+  return attribute;
 }
 
 - (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
@@ -277,7 +345,11 @@ - (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
 
 #pragma mark - Private Methods
 
-// Find the shortest column.
+/**
+ *  Find the shortest column.
+ *
+ *  @return index for the shortest column
+ */
 - (NSUInteger)shortestColumnIndex {
   __block NSUInteger index = 0;
   __block CGFloat shortestHeight = MAXFLOAT;
@@ -293,7 +365,11 @@ - (NSUInteger)shortestColumnIndex {
   return index;
 }
 
-// Find the longest column.
+/**
+ *  Find the longest column.
+ *
+ *  @return index for the longest column
+ */
 - (NSUInteger)longestColumnIndex {
   __block NSUInteger index = 0;
   __block CGFloat longestHeight = 0;

From f0561f2012f3d97c50e43fd77aa0bd94e8669caf Mon Sep 17 00:00:00 2001
From: Andreas Maechler <andreas.maechler@varian.com>
Date: Sat, 8 Feb 2014 11:05:00 -0800
Subject: [PATCH 4/6] Call [super initWithCoder] instead of init

---
 CHTCollectionViewWaterfallLayout.m | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHTCollectionViewWaterfallLayout.m b/CHTCollectionViewWaterfallLayout.m
index 8aa6569..d1f1747 100644
--- a/CHTCollectionViewWaterfallLayout.m
+++ b/CHTCollectionViewWaterfallLayout.m
@@ -92,7 +92,7 @@ - (id)init {
 }
 
 - (id)initWithCoder:(NSCoder *)aDecoder {
-    self = [super init];
+    self = [super initWithCoder:aDecoder];
     if (self) {
         [self commonInit];
     }

From 3d6da7fee212d8683198ba9c261a9a655e2633ba Mon Sep 17 00:00:00 2001
From: Nelson Tai <chiahsien@gmail.com>
Date: Sun, 9 Feb 2014 16:01:26 +0800
Subject: [PATCH 5/6] Change some properties and methods to imitate
 UICollectionViewFlowLayout's usage as much as possible - Don't need to
 calculate item size by yourself. - Also fix some issues with frame
 calculation.

---
 CHTCollectionViewWaterfallLayout.h |  59 +++++++++++++----
 CHTCollectionViewWaterfallLayout.m | 100 ++++++++++++-----------------
 Demo/Demo/ViewController.h         |   1 -
 Demo/Demo/ViewController.m         |  64 ++++++++----------
 README.md                          |  20 +++---
 5 files changed, 126 insertions(+), 118 deletions(-)

diff --git a/CHTCollectionViewWaterfallLayout.h b/CHTCollectionViewWaterfallLayout.h
index 9e9167b..2dba061 100644
--- a/CHTCollectionViewWaterfallLayout.h
+++ b/CHTCollectionViewWaterfallLayout.h
@@ -20,10 +20,18 @@ extern NSString *const CHTCollectionElementKindSectionFooter;
 
 @class CHTCollectionViewWaterfallLayout;
 
+/**
+ *  The CHTCollectionViewDelegateWaterfallLayout protocol defines methods that let you coordinate with a
+ *  CHTCollectionViewWaterfallLayout object to implement a waterfall-based layout.
+ *  The methods of this protocol define the size of items.
+ *
+ *  The waterfall layout object expects the collection view’s delegate object to adopt this protocol.
+ *  Therefore, implement this protocol on object assigned to your collection view’s delegate property.
+ */
 @protocol CHTCollectionViewDelegateWaterfallLayout <UICollectionViewDelegate>
 @required
 /**
- *  Asks the delegate for the height of the specified item’s cell.
+ *  Asks the delegate for the size of the specified item’s cell.
  *
  *  @param collectionView
  *    The collection view object displaying the waterfall layout.
@@ -33,9 +41,9 @@ extern NSString *const CHTCollectionElementKindSectionFooter;
  *    The index path of the item.
  *
  *  @return
- *    The height of the specified item. Must be greater than 0.
+ *    The original size of the specified item. Both width and height must be greater than 0.
  */
-- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout heightForItemAtIndexPath:(NSIndexPath *)indexPath;
+- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath;
 
 @optional
 /**
@@ -73,7 +81,7 @@ extern NSString *const CHTCollectionElementKindSectionFooter;
  *    The height of the footer. If you return 0, no footer is added.
  *
  *  @discussion
- *    If you do not implement this method, the waterfall layout uses the value in its footerHeight property to set the size of the header.
+ *    If you do not implement this method, the waterfall layout uses the value in its footerHeight property to set the size of the footer.
  *
  *  @see
  *    footerHeight
@@ -83,7 +91,22 @@ extern NSString *const CHTCollectionElementKindSectionFooter;
 
 #pragma mark - CHTCollectionViewWaterfallLayout
 
+/**
+ *  The CHTCollectionViewWaterfallLayout class is a concrete layout object that organizes items into waterfall-based grids 
+ *  with optional header and footer views for each section.
+ *
+ *  A waterfall layout works with the collection view’s delegate object to determine the size of items, headers, and footers 
+ *  in each section. That delegate object must conform to the `CHTCollectionViewDelegateWaterfallLayout` protocol.
+ *
+ *  Each section in a waterfall layout can have its own custom header and footer. To configure the header or footer for a view, 
+ *  you must configure the height of the header or footer to be non zero. You can do this by implementing the appropriate delegate 
+ *  methods or by assigning appropriate values to the `headerHeight` and `footerHeight` properties. 
+ *  If the header or footer height is 0, the corresponding view is not added to the collection view.
+ *
+ *  @note CHTCollectionViewWaterfallLayout doesn't support decoration view, and it supports vertical scrolling direction only.
+ */
 @interface CHTCollectionViewWaterfallLayout : UICollectionViewLayout
+
 /**
  *  @brief How many columns for this layout.
  *  @discussion Default: 2
@@ -91,16 +114,24 @@ extern NSString *const CHTCollectionElementKindSectionFooter;
 @property (nonatomic, assign) NSInteger columnCount;
 
 /**
- *  @brief Width for each item.
- *  @discussion Default: 140
+ *  @brief The minimum spacing to use between successive columns.
+ *  @discussion Default: 10.0
  */
-@property (nonatomic, assign) CGFloat itemWidth;
+@property (nonatomic, assign) CGFloat minimumColumnSpacing;
+
+/**
+ *  @brief The minimum spacing to use between items in the same column.
+ *  @discussion Default: 10.0
+ *  @note This spacing is not applied to the space between header and columns or between columns and footer.
+ */
+@property (nonatomic, assign) CGFloat minimumInteritemSpacing;
 
 /**
  *  @brief Height for section header
  *  @discussion
  *    If your collectionView's delegate doesn't implement `collectionView:layout:heightForHeaderInSection:`,
  *    then this value will be used.
+ *
  *    Default: 0
  */
 @property (nonatomic, assign) CGFloat headerHeight;
@@ -110,19 +141,19 @@ extern NSString *const CHTCollectionElementKindSectionFooter;
  *  @discussion
  *    If your collectionView's delegate doesn't implement `collectionView:layout:heightForFooterInSection:`,
  *    then this value will be used.
+ *
  *    Default: 0
  */
 @property (nonatomic, assign) CGFloat footerHeight;
 
 /**
  *  @brief The margins that are used to lay out content in each section.
- *  @discussion Default: UIEdgeInsetsZero
+ *  @discussion
+ *    Section insets are margins applied only to the items in the section. 
+ *    They represent the distance between the header view and the columns and between the columns and the footer view. 
+ *    They also indicate the spacing on either side of columns. They do not affect the size of the headers or footers themselves.
+ *
+ *    Default: UIEdgeInsetsZero
  */
 @property (nonatomic, assign) UIEdgeInsets sectionInset;
-
-/**
- *  @brief Spacing between items vertically.
- *  @discussion It will be calculated automatically if you don't assign a value.
- */
-@property (nonatomic, assign) CGFloat verticalItemSpacing;
 @end
diff --git a/CHTCollectionViewWaterfallLayout.m b/CHTCollectionViewWaterfallLayout.m
index 91371d8..5a966ee 100644
--- a/CHTCollectionViewWaterfallLayout.m
+++ b/CHTCollectionViewWaterfallLayout.m
@@ -11,7 +11,7 @@
 NSString *const CHTCollectionElementKindSectionFooter = @"CHTCollectionElementKindSectionFooter";
 
 @interface CHTCollectionViewWaterfallLayout ()
-/// The delegate will point to collectionView.delegate automatically.
+/// The delegate will point to collection view's delegate automatically.
 @property (nonatomic, weak) id <CHTCollectionViewDelegateWaterfallLayout> delegate;
 /// Array to store height for each column
 @property (nonatomic, strong) NSMutableArray *columnHeights;
@@ -25,10 +25,8 @@ @interface CHTCollectionViewWaterfallLayout ()
 @property (nonatomic, strong) NSMutableDictionary *footersAttrubite;
 /// Array to store union rectangles
 @property (nonatomic, strong) NSMutableArray *unionRects;
-/// Inter spacing at X-axis for each item
-@property (nonatomic, assign) CGFloat interItemSpacingX;
-/// Inter spacing at Y-axis for each item
-@property (nonatomic, assign) CGFloat interItemSpacingY;
+/// Width for each item
+@property (nonatomic, assign) CGFloat itemWidth;
 @end
 
 @implementation CHTCollectionViewWaterfallLayout
@@ -36,7 +34,7 @@ @implementation CHTCollectionViewWaterfallLayout
 /// How many items to be union into a single rectangle
 const NSInteger unionSize = 20;
 
-#pragma mark - Accessors
+#pragma mark - Public Accessors
 - (void)setColumnCount:(NSInteger)columnCount {
   if (_columnCount != columnCount) {
     _columnCount = columnCount;
@@ -44,9 +42,16 @@ - (void)setColumnCount:(NSInteger)columnCount {
   }
 }
 
-- (void)setItemWidth:(CGFloat)itemWidth {
-  if (_itemWidth != itemWidth) {
-    _itemWidth = itemWidth;
+- (void)setMinimumColumnSpacing:(CGFloat)minimumColumnSpacing {
+  if (_minimumColumnSpacing != minimumColumnSpacing) {
+    _minimumColumnSpacing = minimumColumnSpacing;
+    [self invalidateLayout];
+  }
+}
+
+- (void)setMinimumInteritemSpacing:(CGFloat)minimumInteritemSpacing {
+  if (_minimumInteritemSpacing != minimumInteritemSpacing) {
+    _minimumInteritemSpacing = minimumInteritemSpacing;
     [self invalidateLayout];
   }
 }
@@ -72,13 +77,7 @@ - (void)setSectionInset:(UIEdgeInsets)sectionInset {
   }
 }
 
-- (void)setVerticalItemSpacing:(CGFloat)verticalItemSpacing {
-  if (_verticalItemSpacing != verticalItemSpacing) {
-    _verticalItemSpacing = verticalItemSpacing;
-    [self invalidateLayout];
-  }
-}
-
+#pragma mark - Private Accessors
 - (NSMutableDictionary *)headersAttribute {
   if (!_headersAttribute) {
     _headersAttribute = [NSMutableDictionary dictionary];
@@ -124,19 +123,17 @@ - (NSMutableArray *)sectionItemAttributes {
 #pragma mark - Init
 - (void)commonInit {
   _columnCount = 2;
-  _itemWidth = 140;
+  _minimumColumnSpacing = 10;
+  _minimumInteritemSpacing = 10;
   _headerHeight = 0;
   _footerHeight = 0;
-  _verticalItemSpacing = 0;
   _sectionInset = UIEdgeInsetsZero;
-  _delegate = (id <CHTCollectionViewDelegateWaterfallLayout> )self.collectionView.delegate;
 }
 
 - (id)init {
   if (self = [super init]) {
     [self commonInit];
   }
-
   return self;
 }
 
@@ -144,7 +141,6 @@ - (id)initWithCoder:(NSCoder *)aDecoder {
   if (self = [super initWithCoder:aDecoder]) {
     [self commonInit];
   }
-
   return self;
 }
 
@@ -157,22 +153,15 @@ - (void)prepareLayout {
     return;
   }
 
-  NSAssert(self.columnCount > 0, @"columnCount for UICollectionViewWaterfallLayout should be greater than 0.");
+  self.delegate = (id <CHTCollectionViewDelegateWaterfallLayout> )self.collectionView.delegate;
+  NSAssert([self.delegate conformsToProtocol:@protocol(CHTCollectionViewDelegateWaterfallLayout)], @"UICollectionView's delegate should conform to CHTCollectionViewDelegateWaterfallLayout protocol");
+  NSAssert(self.columnCount > 0, @"UICollectionViewWaterfallLayout's columnCount should be greater than 0");
 
   // Initialize variables
   NSInteger idx = 0;
   CGFloat width = self.collectionView.frame.size.width - self.sectionInset.left - self.sectionInset.right;
 
-  if (self.columnCount > 1) {
-    self.interItemSpacingX = floorf((width - self.columnCount * self.itemWidth) / (self.columnCount - 1));
-  } else {
-    self.interItemSpacingX = floorf((width - self.itemWidth) / 2);
-  }
-  if (self.verticalItemSpacing > 0) {
-    self.interItemSpacingY = self.verticalItemSpacing;
-  } else {
-    self.interItemSpacingY = self.interItemSpacingX;
-  }
+  self.itemWidth = floorf((width - (self.columnCount - 1) * self.minimumColumnSpacing) / self.columnCount);
 
   [self.headersAttribute removeAllObjects];
   [self.footersAttrubite removeAllObjects];
@@ -186,7 +175,7 @@ - (void)prepareLayout {
   }
 
   // Create attributes
-  CGFloat sectionTop = self.sectionInset.top;
+  CGFloat top = 0;
   UICollectionViewLayoutAttributes *attributes;
 
   for (NSInteger section = 0; section < numberOfSections; ++section) {
@@ -202,18 +191,17 @@ - (void)prepareLayout {
 
     if (headerHeight > 0) {
       attributes = [UICollectionViewLayoutAttributes layoutAttributesForSupplementaryViewOfKind:CHTCollectionElementKindSectionHeader withIndexPath:[NSIndexPath indexPathForItem:0 inSection:section]];
-      attributes.frame = CGRectMake(self.sectionInset.left, sectionTop, width, headerHeight);
+      attributes.frame = CGRectMake(0, top, self.collectionView.frame.size.width, headerHeight);
 
       self.headersAttribute[@(section)] = attributes;
       [self.allItemAttributes addObject:attributes];
 
-      for (idx = 0; idx < self.columnCount; idx++) {
-        self.columnHeights[idx] = @(CGRectGetMaxY(attributes.frame) + self.interItemSpacingY);
-      }
-    } else {
-      for (idx = 0; idx < self.columnCount; idx++) {
-        self.columnHeights[idx] = @(sectionTop);
-      }
+      top = CGRectGetMaxY(attributes.frame);
+    }
+
+    top += self.sectionInset.top;
+    for (idx = 0; idx < self.columnCount; idx++) {
+      self.columnHeights[idx] = @(top);
     }
 
     /*
@@ -225,16 +213,17 @@ - (void)prepareLayout {
     // Item will be put into shortest column.
     for (idx = 0; idx < itemCount; idx++) {
       NSIndexPath *indexPath = [NSIndexPath indexPathForItem:idx inSection:section];
-      CGFloat itemHeight = [self.delegate collectionView:self.collectionView layout:self heightForItemAtIndexPath:indexPath];
+      CGSize itemSize = [self.delegate collectionView:self.collectionView layout:self sizeForItemAtIndexPath:indexPath];
+      CGFloat itemHeight = floorf(itemSize.height * self.itemWidth / itemSize.width);
       NSUInteger columnIndex = [self shortestColumnIndex];
-      CGFloat xOffset = self.sectionInset.left + (self.itemWidth + self.interItemSpacingX) * columnIndex;
+      CGFloat xOffset = self.sectionInset.left + (self.itemWidth + self.minimumColumnSpacing) * columnIndex;
       CGFloat yOffset = [self.columnHeights[columnIndex] floatValue];
 
       attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
       attributes.frame = CGRectMake(xOffset, yOffset, self.itemWidth, itemHeight);
       [itemAttributes addObject:attributes];
       [self.allItemAttributes addObject:attributes];
-      self.columnHeights[columnIndex] = @(yOffset + itemHeight + self.interItemSpacingY);
+      self.columnHeights[columnIndex] = @(CGRectGetMaxY(attributes.frame) + self.minimumInteritemSpacing);
     }
 
     [self.sectionItemAttributes addObject:itemAttributes];
@@ -242,9 +231,9 @@ - (void)prepareLayout {
     /*
      * Section footer
      */
-    NSUInteger columnIndex = [self longestColumnIndex];
-    CGFloat yOffset = [self.columnHeights[columnIndex] floatValue];
     CGFloat footerHeight;
+    NSUInteger columnIndex = [self longestColumnIndex];
+    top = [self.columnHeights[columnIndex] floatValue] - self.minimumInteritemSpacing + self.sectionInset.bottom;
 
     if ([self.delegate respondsToSelector:@selector(collectionView:layout:heightForFooterInSection:)]) {
       footerHeight = [self.delegate collectionView:self.collectionView layout:self heightForFooterInSection:section];
@@ -254,20 +243,16 @@ - (void)prepareLayout {
 
     if (footerHeight > 0) {
       attributes = [UICollectionViewLayoutAttributes layoutAttributesForSupplementaryViewOfKind:CHTCollectionElementKindSectionFooter withIndexPath:[NSIndexPath indexPathForItem:0 inSection:section]];
-      attributes.frame = CGRectMake(self.sectionInset.left, yOffset, width, footerHeight);
+      attributes.frame = CGRectMake(0, top, self.collectionView.frame.size.width, footerHeight);
 
       self.footersAttrubite[@(section)] = attributes;
       [self.allItemAttributes addObject:attributes];
 
-      sectionTop = CGRectGetMaxY(attributes.frame) + self.interItemSpacingY;
-      for (idx = 0; idx < self.columnCount; idx++) {
-        self.columnHeights[idx] = @(sectionTop);
-      }
-    } else {
-      sectionTop = yOffset + self.interItemSpacingY;
-      for (idx = 0; idx < self.columnCount; idx++) {
-        self.columnHeights[idx] = @(sectionTop);
-      }
+      top = CGRectGetMaxY(attributes.frame);
+    }
+
+    for (idx = 0; idx < self.columnCount; idx++) {
+      self.columnHeights[idx] = @(top);
     }
   } // end of for (NSInteger section = 0; section < numberOfSections; ++section)
 
@@ -290,8 +275,7 @@ - (CGSize)collectionViewContentSize {
   }
 
   CGSize contentSize = self.collectionView.bounds.size;
-  CGFloat height = [self.columnHeights[0] floatValue];
-  contentSize.height = height - self.interItemSpacingY + self.sectionInset.bottom;
+  contentSize.height = [self.columnHeights[0] floatValue];
 
   return contentSize;
 }
diff --git a/Demo/Demo/ViewController.h b/Demo/Demo/ViewController.h
index 6d3782c..0106a90 100644
--- a/Demo/Demo/ViewController.h
+++ b/Demo/Demo/ViewController.h
@@ -11,5 +11,4 @@
 
 @interface ViewController : UIViewController <UICollectionViewDataSource, CHTCollectionViewDelegateWaterfallLayout>
 @property (nonatomic, strong) IBOutlet UICollectionView *collectionView;
-@property (nonatomic) CGFloat cellWidth;
 @end
diff --git a/Demo/Demo/ViewController.m b/Demo/Demo/ViewController.m
index e7408b7..622982e 100644
--- a/Demo/Demo/ViewController.m
+++ b/Demo/Demo/ViewController.m
@@ -11,34 +11,28 @@
 #import "CHTCollectionViewWaterfallHeader.h"
 #import "CHTCollectionViewWaterfallFooter.h"
 
-#define CELL_WIDTH 140
-#define CELL_COUNT 50
+#define CELL_COUNT 30
 #define CELL_IDENTIFIER @"WaterfallCell"
 #define HEADER_IDENTIFIER @"WaterfallHeader"
 #define FOOTER_IDENTIFIER @"WaterfallFooter"
 
 @interface ViewController ()
-@property (nonatomic, strong) NSMutableArray *cellHeights;
+@property (nonatomic, strong) NSMutableArray *cellSizes;
 @end
 
 @implementation ViewController
 
-- (id)initWithCoder:(NSCoder *)aDecoder {
-  if (self = [super initWithCoder:aDecoder]) {
-    self.cellWidth = CELL_WIDTH;    // Default if not setting runtime attribute
-  }
-  return self;
-}
-
 #pragma mark - Accessors
+
 - (UICollectionView *)collectionView {
   if (!_collectionView) {
     CHTCollectionViewWaterfallLayout *layout = [[CHTCollectionViewWaterfallLayout alloc] init];
 
-    layout.sectionInset = UIEdgeInsetsMake(9, 9, 9, 9);
-    layout.verticalItemSpacing = 5;
+    layout.sectionInset = UIEdgeInsetsMake(10, 10, 10, 10);
     layout.headerHeight = 15;
     layout.footerHeight = 10;
+    layout.minimumColumnSpacing = 20;
+    layout.minimumInteritemSpacing = 30;
 
     _collectionView = [[UICollectionView alloc] initWithFrame:self.view.bounds collectionViewLayout:layout];
     _collectionView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
@@ -57,17 +51,19 @@ - (UICollectionView *)collectionView {
   return _collectionView;
 }
 
-- (NSMutableArray *)cellHeights {
-  if (!_cellHeights) {
-    _cellHeights = [NSMutableArray arrayWithCapacity:CELL_COUNT];
+- (NSMutableArray *)cellSizes {
+  if (!_cellSizes) {
+    _cellSizes = [NSMutableArray array];
     for (NSInteger i = 0; i < CELL_COUNT; i++) {
-      _cellHeights[i] = @(arc4random() % 100 * 2 + 100);
+      CGSize size = CGSizeMake(arc4random() % 50 + 50, arc4random() % 50 + 50);
+      _cellSizes[i] = [NSValue valueWithCGSize:size];
     }
   }
-  return _cellHeights;
+  return _cellSizes;
 }
 
 #pragma mark - Life Cycle
+
 - (void)dealloc {
   _collectionView.delegate = nil;
   _collectionView.dataSource = nil;
@@ -80,24 +76,22 @@ - (void)viewDidLoad {
 
 - (void)viewDidAppear:(BOOL)animated {
   [super viewDidAppear:animated];
-  [self updateLayout];
+  [self updateLayoutForOrientation:[UIApplication sharedApplication].statusBarOrientation];
 }
 
-- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
-                                         duration:(NSTimeInterval)duration {
-  [super willAnimateRotationToInterfaceOrientation:toInterfaceOrientation
-                                          duration:duration];
-  [self updateLayout];
+- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
+  [super willAnimateRotationToInterfaceOrientation:toInterfaceOrientation duration:duration];
+  [self updateLayoutForOrientation:toInterfaceOrientation];
 }
 
-- (void)updateLayout {
+- (void)updateLayoutForOrientation:(UIInterfaceOrientation)orientation {
   CHTCollectionViewWaterfallLayout *layout =
-  (CHTCollectionViewWaterfallLayout *)self.collectionView.collectionViewLayout;
-  layout.columnCount = self.collectionView.bounds.size.width / self.cellWidth;
-  layout.itemWidth = self.cellWidth;
+    (CHTCollectionViewWaterfallLayout *)self.collectionView.collectionViewLayout;
+  layout.columnCount = UIInterfaceOrientationIsPortrait(orientation) ? 2 : 3;
 }
 
 #pragma mark - UICollectionViewDataSource
+
 - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
   return CELL_COUNT;
 }
@@ -108,15 +102,13 @@ - (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
 
 - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
   CHTCollectionViewWaterfallCell *cell =
-  (CHTCollectionViewWaterfallCell *)[collectionView dequeueReusableCellWithReuseIdentifier:CELL_IDENTIFIER
-                                                                              forIndexPath:indexPath];
+    (CHTCollectionViewWaterfallCell *)[collectionView dequeueReusableCellWithReuseIdentifier:CELL_IDENTIFIER
+                                                                                forIndexPath:indexPath];
   cell.displayString = [NSString stringWithFormat:@"%d", indexPath.item];
   return cell;
 }
 
-- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView
-           viewForSupplementaryElementOfKind:(NSString *)kind
-                                 atIndexPath:(NSIndexPath *)indexPath {
+- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
   UICollectionReusableView *reusableView = nil;
 
   if ([kind isEqualToString:CHTCollectionElementKindSectionHeader]) {
@@ -132,11 +124,9 @@ - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView
   return reusableView;
 }
 
-#pragma mark - UICollectionViewWaterfallLayoutDelegate
-- (CGFloat)   collectionView:(UICollectionView *)collectionView
-                      layout:(CHTCollectionViewWaterfallLayout *)collectionViewLayout
-    heightForItemAtIndexPath:(NSIndexPath *)indexPath {
-  return [self.cellHeights[indexPath.item] floatValue];
+#pragma mark - CHTCollectionViewDelegateWaterfallLayout
+- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
+  return [self.cellSizes[indexPath.item] CGSizeValue];
 }
 
 @end
diff --git a/README.md b/README.md
index fe450a2..1308030 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@ CHTCollectionViewWaterfallLayout
 [![Version](https://cocoapod-badges.herokuapp.com/v/CHTCollectionViewWaterfallLayout/badge.png)](http://cocoadocs.org/docsets/CHTCollectionViewWaterfallLayout)
 [![Platform](https://cocoapod-badges.herokuapp.com/p/CHTCollectionViewWaterfallLayout/badge.png)](http://cocoadocs.org/docsets/CHTCollectionViewWaterfallLayout)
 
-iOS 6 introduced a new feature called [UICollectionView]. **CHTCollectionViewWaterfallLayout** is a subclass of [UICollectionViewLayout], and it trys to imitate [UICollectionViewFlowLayout]'s usage as much as possible.
+**CHTCollectionViewWaterfallLayout** is a subclass of [UICollectionViewLayout], and it trys to imitate [UICollectionViewFlowLayout]'s usage as much as possible.
 
 This layout is inspired by [Pinterest]. It also is compatible with [PSTCollectionView].
 
@@ -25,24 +25,22 @@ How to Use
 Read the demo codes and `CHTCollectionViewWaterfallLayout.h` header file for more information.
 
 #### Step 1
-There are some properties for you. Although they have default values, I strongly recommand you to set up `columnCount` and `itemWidth` to suit your needs.
+There are some properties for you. Although they have default values, I strongly recommand you to set up `columnCount` to suit your needs.
 
 ``` objc
 @property (nonatomic, assign) NSInteger columnCount;
-@property (nonatomic, assign) CGFloat itemWidth;
+@property (nonatomic, assign) CGFloat minimumColumnSpacing;
+@property (nonatomic, assign) CGFloat minimumInteritemSpacing;
 @property (nonatomic, assign) CGFloat headerHeight;
 @property (nonatomic, assign) CGFloat footerHeight;
 @property (nonatomic, assign) UIEdgeInsets sectionInset;
-@property (nonatomic, assign) CGFloat verticalItemSpacically
 ```
 
 #### Step 2
 Your collectionView's delegate (which often is your view controller) must conforms to `CHTCollectionViewDelegateWaterfallLayout` protocol and implements the required method:
 
 ``` objc
-- (CGFloat)collectionView:(UICollectionView *)collectionView
-                   layout:(UICollectionViewLayout *)collectionViewLayout
- heightForItemAtIndexPath:(NSIndexPath *)indexPath;
+- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath;
 ```
 
 #### Step 3 (Optional)
@@ -63,6 +61,13 @@ CHTCollectionViewWaterfallLayout is available under the MIT license. See the LIC
 
 Changelog
 ---------
+#### 0.0.6
+* [Add] Add `minimumColumnSpacing` and `minimumInteritemSpacing` properties.
+* [Remove] Remove `itemWidth` property. The layout object will calculate a proper item width automatically.
+* [Change] Rename delegate method `- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout heightForItemAtIndexPath:(NSIndexPath *)indexPath` to `- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath`. It should return original size for each item.
+* [Fix] Section header and/or footer should work properly.
+* [Fix] Use `sectionInset` correctly.
+
 #### 0.0.5
 * [Add] Multiple sections.
 * [Add] Header and/or footer for section.
@@ -70,7 +75,6 @@ Changelog
 * [Change] Remove `delegate` property, your collectionView's delegate **MUST** conforms to `<CHTCollectionViewDelegateWaterfallLayout>` protocol.
 
 
-[UICollectionView]: http://developer.apple.com/library/ios/#documentation/uikit/reference/UICollectionView_class/Reference/Reference.html
 [UICollectionViewLayout]: http://developer.apple.com/library/ios/#documentation/uikit/reference/UICollectionViewLayout_class/Reference/Reference.html
 [UICollectionViewFlowLayout]: https://developer.apple.com/library/ios/documentation/uikit/reference/UICollectionViewFlowLayout_class/Reference/Reference.html
 [Pinterest]: http://pinterest.com/

From c47a2c1fe2bcf748fd86a5de6dc28b0dcd793793 Mon Sep 17 00:00:00 2001
From: Nelson Tai <chiahsien@gmail.com>
Date: Mon, 17 Feb 2014 00:33:19 +0800
Subject: [PATCH 6/6] Update podspec and README

---
 CHTCollectionViewWaterfallLayout.podspec |  2 +-
 README.md                                | 15 +++++++++++----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/CHTCollectionViewWaterfallLayout.podspec b/CHTCollectionViewWaterfallLayout.podspec
index 066ed39..39200d9 100644
--- a/CHTCollectionViewWaterfallLayout.podspec
+++ b/CHTCollectionViewWaterfallLayout.podspec
@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = "CHTCollectionViewWaterfallLayout"
-  s.version      = "0.5"
+  s.version      = "0.6"
   s.summary      = "The waterfall (i.e., Pinterest-like) layout for UICollectionView."
   s.homepage     = "https://github.com/chiahsien/CHTCollectionViewWaterfallLayout"
   s.screenshots  = "https://raw.github.com/chiahsien/UICollectionViewWaterfallLayout/master/Screenshots/2-columns.png", "https://raw.github.com/chiahsien/UICollectionViewWaterfallLayout/master/Screenshots/3-columns.png"
diff --git a/README.md b/README.md
index 1308030..28defda 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,13 @@ Screen Shots
 ![2 columns](https://raw.github.com/chiahsien/UICollectionViewWaterfallLayout/master/Screenshots/2-columns.png)
 ![3 columns](https://raw.github.com/chiahsien/UICollectionViewWaterfallLayout/master/Screenshots/3-columns.png)
 
+Features
+--------
+* Easy to use, it trys to imitate [UICollectionViewFlowLayout]'s usage as much as possible.
+* Highly customizable.
+* Outstanding performance, try 10,000+ items and see the smoothness for yourself.
+* Support header and footer views.
+
 Prerequisite
 ------------
 * ARC
@@ -25,7 +32,7 @@ How to Use
 Read the demo codes and `CHTCollectionViewWaterfallLayout.h` header file for more information.
 
 #### Step 1
-There are some properties for you. Although they have default values, I strongly recommand you to set up `columnCount` to suit your needs.
+Below lists the properties for you to customize the layout. Although they have default values, I strongly recommand you to set up at least the `columnCount` property to suit your needs.
 
 ``` objc
 @property (nonatomic, assign) NSInteger columnCount;
@@ -37,7 +44,7 @@ There are some properties for you. Although they have default values, I strongly
 ```
 
 #### Step 2
-Your collectionView's delegate (which often is your view controller) must conforms to `CHTCollectionViewDelegateWaterfallLayout` protocol and implements the required method:
+Your collection view's delegate (which often is your view controller) must conforms to `CHTCollectionViewDelegateWaterfallLayout` protocol and implements the required method, all you need to do is return the original size of the item:
 
 ``` objc
 - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath;
@@ -61,14 +68,14 @@ CHTCollectionViewWaterfallLayout is available under the MIT license. See the LIC
 
 Changelog
 ---------
-#### 0.0.6
+#### 0.6
 * [Add] Add `minimumColumnSpacing` and `minimumInteritemSpacing` properties.
 * [Remove] Remove `itemWidth` property. The layout object will calculate a proper item width automatically.
 * [Change] Rename delegate method `- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout heightForItemAtIndexPath:(NSIndexPath *)indexPath` to `- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath`. It should return original size for each item.
 * [Fix] Section header and/or footer should work properly.
 * [Fix] Use `sectionInset` correctly.
 
-#### 0.0.5
+#### 0.5
 * [Add] Multiple sections.
 * [Add] Header and/or footer for section.
 * [Add] More properties and delegation methods.