Use CADisplayLink instead of NSTimer to know when to redraw on scroll.

Author: Zach Drayer

LXRCVFL Example using Storyboard/LXRCVFL Example using Storyboard.xcodeproj/project.pbxproj

@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		927A97F41736CA0E00539F5E /* QuartzCore.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 927A97F31736CA0E00539F5E /* QuartzCore.framework */; };
 		AB0E97C7161B4BEC005498A0 /* UIKit.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = AB0E97C6161B4BEC005498A0 /* UIKit.framework */; };
 		AB0E97C9161B4BEC005498A0 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = AB0E97C8161B4BEC005498A0 /* Foundation.framework */; };
 		AB0E97CB161B4BEC005498A0 /* CoreGraphics.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = AB0E97CA161B4BEC005498A0 /* CoreGraphics.framework */; };
@@ -25,6 +26,7 @@
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
+		927A97F31736CA0E00539F5E /* QuartzCore.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = QuartzCore.framework; path = System/Library/Frameworks/QuartzCore.framework; sourceTree = SDKROOT; };
 		AB0E97C2161B4BEC005498A0 /* LXRCVFL Example using Storyboard.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = "LXRCVFL Example using Storyboard.app"; sourceTree = BUILT_PRODUCTS_DIR; };
 		AB0E97C6161B4BEC005498A0 /* UIKit.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = UIKit.framework; path = System/Library/Frameworks/UIKit.framework; sourceTree = SDKROOT; };
 		AB0E97C8161B4BEC005498A0 /* Foundation.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = Foundation.framework; path = System/Library/Frameworks/Foundation.framework; sourceTree = SDKROOT; };
@@ -55,6 +57,7 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				927A97F41736CA0E00539F5E /* QuartzCore.framework in Frameworks */,
 				AB0E97C7161B4BEC005498A0 /* UIKit.framework in Frameworks */,
 				AB0E97C9161B4BEC005498A0 /* Foundation.framework in Frameworks */,
 				AB0E97CB161B4BEC005498A0 /* CoreGraphics.framework in Frameworks */,
@@ -86,6 +89,7 @@
 		AB0E97C5161B4BEC005498A0 /* Frameworks */ = {
 			isa = PBXGroup;
 			children = (
+				927A97F31736CA0E00539F5E /* QuartzCore.framework */,
 				AB0E97C6161B4BEC005498A0 /* UIKit.framework */,
 				AB0E97C8161B4BEC005498A0 /* Foundation.framework */,
 				AB0E97CA161B4BEC005498A0 /* CoreGraphics.framework */,

LXReorderableCollectionViewFlowLayout/LXReorderableCollectionViewFlowLayout.m

@@ -7,6 +7,7 @@
 
 #import "LXReorderableCollectionViewFlowLayout.h"
 #import <QuartzCore/QuartzCore.h>
+#import <objc/runtime.h>
 
 #define LX_FRAMES_PER_SECOND 60.0
 
@@ -28,6 +29,20 @@ typedef NS_ENUM(NSInteger, LXScrollingDirection) {
 static NSString * const kLXScrollingDirectionKey = @"LXScrollingDirection";
 static NSString * const kLXCollectionViewKeyPath = @"collectionView";
 
+@interface CADisplayLink (LX_userInfo)
+@property (nonatomic, copy) NSDictionary *LX_userInfo;
+@end
+
+@implementation CADisplayLink (LX_userInfo)
+- (void) setLX_userInfo:(NSDictionary *) LX_userInfo {
+    objc_setAssociatedObject(self, "LX_userInfo", LX_userInfo, OBJC_ASSOCIATION_COPY);
+}
+
+- (NSDictionary *) LX_userInfo {
+    return objc_getAssociatedObject(self, "LX_userInfo");
+}
+@end
+
 @interface UICollectionViewCell (LXReorderableCollectionViewFlowLayout)
 
 - (UIImage *)LX_rasterizedImage;
@@ -52,7 +67,7 @@ @interface LXReorderableCollectionViewFlowLayout ()
 @property (strong, nonatomic) UIView *currentView;
 @property (assign, nonatomic) CGPoint currentViewCenter;
 @property (assign, nonatomic) CGPoint panTranslationInCollectionView;
-@property (strong, nonatomic) NSTimer *scrollingTimer;
+@property (strong, nonatomic) CADisplayLink *displayLink;
 
 @property (assign, nonatomic, readonly) id<LXReorderableCollectionViewDataSource> dataSource;
 @property (assign, nonatomic, readonly) id<LXReorderableCollectionViewDelegateFlowLayout> delegate;
@@ -152,35 +167,34 @@ - (void)invalidateLayoutIfNecessary {
 }
 
 - (void)invalidatesScrollTimer {
-    if (self.scrollingTimer.isValid) {
-        [self.scrollingTimer invalidate];
+    if (!self.displayLink.paused) {
+        [self.displayLink invalidate];
     }
-    self.scrollingTimer = nil;
+    self.displayLink = nil;
 }
 
 - (void)setupScrollTimerInDirection:(LXScrollingDirection)direction {
-    if (self.scrollingTimer.isValid) {
-        LXScrollingDirection oldDirection = [self.scrollingTimer.userInfo[kLXScrollingDirectionKey] integerValue];
-        
+    if (!self.displayLink.paused) {
+        LXScrollingDirection oldDirection = [self.displayLink.LX_userInfo[kLXScrollingDirectionKey] integerValue];
+
         if (direction == oldDirection) {
             return;
         }
     }
 
     [self invalidatesScrollTimer];
-    
-    self.scrollingTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 / LX_FRAMES_PER_SECOND
-                                                           target:self
-                                                         selector:@selector(handleScroll:)
-                                                         userInfo:@{ kLXScrollingDirectionKey : @(direction) }
-                                                          repeats:YES];
+
+    self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(handleScroll:)];
+    self.displayLink.LX_userInfo = @{ kLXScrollingDirectionKey : @(direction) };
+
+    [self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
 }
 
 #pragma mark - Target/Action methods
 
 // Tight loop, allocate memory sparely, even if they are stack allocation.
-- (void)handleScroll:(NSTimer *)timer {
-    LXScrollingDirection direction = (LXScrollingDirection)[timer.userInfo[kLXScrollingDirectionKey] integerValue];
+- (void)handleScroll:(CADisplayLink *)displayLink {
+    LXScrollingDirection direction = (LXScrollingDirection)[displayLink.LX_userInfo[kLXScrollingDirectionKey] integerValue];
     if (direction == LXScrollingDirectionUnknown) {
         return;
     }