Make animated image can resume from next frame after switch back to specified runloop mode

Source/Classes/AnimatedImages/PINAnimatedImageView.m

@@ -23,8 +23,6 @@ @interface PINAnimatedImageView ()
 @property (nonatomic, assign) CGImageRef frameImage;
 @property (nonatomic, strong) PINDisplayLink *displayLink;
 
-@property (nonatomic, assign) CFTimeInterval lastDisplayLinkFire;
-
 @end
 
 @implementation PINAnimatedImageView
@@ -239,7 +237,6 @@ - (void)stopAnimating
     PINAssertMain();
 
     _displayLink.paused = YES;
-    _lastDisplayLinkFire = 0;
 
     [_animatedImage clearAnimatedImageCache];
 }
@@ -352,14 +349,11 @@ - (void)updateAnimationForPossibleVisibility
 - (void)displayLinkFired:(PINDisplayLink *)displayLink
 {
     PINAssertMain();
-    CFTimeInterval timeBetweenLastFire;
-    if (_lastDisplayLinkFire == 0) {
-        timeBetweenLastFire = 0;
-    } else {
-        timeBetweenLastFire = CACurrentMediaTime() - self.lastDisplayLinkFire;
-    }
-
-    self.lastDisplayLinkFire = CACurrentMediaTime();
+#if PIN_TARGET_MAC
+    CFTimeInterval timeBetweenLastFire = displayLink.duration;
+#else
+    CFTimeInterval timeBetweenLastFire = displayLink.duration * displayLink.frameInterval;
+#endif
 
     _playHead += timeBetweenLastFire;
 
@@ -383,7 +377,7 @@ - (void)displayLinkFired:(PINDisplayLink *)displayLink
     if (frameImage == nil) {
         //Pause the display link until we get a file ready notification
         displayLink.paused = YES;
-        self.lastDisplayLinkFire = 0;
+        _playHead = MAX(_playHead - timeBetweenLastFire, 0);
     } else {
         if (_frameImage) {
             CGImageRelease(_frameImage);

Source/Classes/PINDisplayLink.h

@@ -20,6 +20,7 @@
 
 @property(getter=isPaused, nonatomic) BOOL paused;
 @property(nonatomic) NSInteger frameInterval;
+@property(nonatomic, readonly) CFTimeInterval duration;
 
 @end
 #endif

Source/Classes/PINDisplayLink.m

@@ -16,7 +16,7 @@ @interface PINDisplayLink ()
 @property (nonatomic, readonly) NSRunLoop *runloop;
 @property (nonatomic, readonly) NSRunLoopMode mode;
 
-- (void)displayLinkFired;
+- (void)displayLinkFiredWithDuration:(CFTimeInterval)duration;
 
 @end
 
@@ -27,8 +27,9 @@ static CVReturn displayLinkFired (CVDisplayLinkRef displayLink,
                                   CVOptionFlags *flagsOut,
                                   void *displayLinkContext)
 {
+    CFTimeInterval duration = inOutputTime->videoRefreshPeriod / (inOutputTime->videoTimeScale * inOutputTime->rateScalar);
     PINDisplayLink *link = (__bridge PINDisplayLink *)displayLinkContext;
-    [link displayLinkFired];
+    [link displayLinkFiredWithDuration:duration];
     return kCVReturnSuccess;
 }
 
@@ -38,6 +39,7 @@ @implementation PINDisplayLink
 
     BOOL _paused;
     NSInteger _frameInterval;
+    CFTimeInterval _duration;
 }
 
 + (PINDisplayLink *)displayLinkWithTarget:(id)target selector:(SEL)sel
@@ -63,9 +65,10 @@ - (void)dealloc
     }
 }
 
-- (void)displayLinkFired
+- (void)displayLinkFiredWithDuration:(CFTimeInterval)duration
 {
     dispatch_async(dispatch_get_main_queue(), ^{
+        self.duration = duration;
         [self.runloop performSelector:self.selector target:self.target argument:self order:NSUIntegerMax modes:@[self.mode]];
     });
 }
@@ -111,6 +114,18 @@ - (void)setPaused:(BOOL)paused
     }
 }
 
+- (CFTimeInterval)duration
+{
+    PINAssertMain();
+    return _duration;
+}
+
+- (void)setDuration:(CFTimeInterval)duration
+{
+    PINAssertMain();
+    _duration = duration;
+}
+
 - (NSInteger)frameInterval
 {
     PINAssertMain();