Fixes an issue with GIFs that would always be covered by their placeholder (#326)

Also adds a subclass override for when the animated image is set.

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## master
 
 * Add your own contributions to the next release on the line below this with your name.
+- Fixed an issue where GIFs with placeholders never had their placeholders uncover the GIF. [Garrett Moon](https://github.com/garrettmoon)
 - [Yoga] Implement ASYogaLayoutSpec, a simplified integration strategy for Yoga-powered layout calculation. [Scott Goodson](https://github.com/appleguy)
 - Fixed an issue where calls to setNeedsDisplay and setNeedsLayout would stop working on loaded nodes. [Garrett Moon](https://github.com/garrettmoon)
 - [ASTextKitFontSizeAdjuster] [Ricky Cancro] Replace use of NSAttributedString's boundingRectWithSize:options:context: with NSLayoutManager's boundingRectForGlyphRange:inTextContainer:

Source/ASImageNode+AnimatedImage.mm

@@ -53,6 +53,7 @@ NSString *const ASAnimatedImageDefaultRunLoopMode = NSRunLoopCommonModes;
     return;
   }
   
+  id <ASAnimatedImageProtocol> previousAnimatedImage = _animatedImage;
   _animatedImage = animatedImage;
   
   if (animatedImage != nil) {
@@ -73,6 +74,13 @@ NSString *const ASAnimatedImageDefaultRunLoopMode = NSRunLoopCommonModes;
       };
     }
   }
+  
+  [self animatedImageSet:_animatedImage previousAnimatedImage:previousAnimatedImage];
+}
+
+- (void)animatedImageSet:(id <ASAnimatedImageProtocol>)newAnimatedImage previousAnimatedImage:(id <ASAnimatedImageProtocol>)previousAnimatedImage
+{
+  //Subclasses may override
 }
 
 - (id <ASAnimatedImageProtocol>)animatedImage
@@ -301,6 +309,7 @@ NSString *const ASAnimatedImageDefaultRunLoopMode = NSRunLoopCommonModes;
     self.lastDisplayLinkFire = 0;
   } else {
     self.contents = (__bridge id)frameImage;
+    [self displayDidFinish];
   }
 }
 

Source/ASImageNode.h

@@ -148,6 +148,9 @@ typedef UIImage * _Nullable (^asimagenode_modification_block_t)(UIImage *image);
  *
  * @discussion Set this to an object which conforms to ASAnimatedImageProtocol
  * to have the ASImageNode playback an animated image.
+ * @warning this method should not be overridden, it may not always be called as
+ * another method is used internally. If you need to know when the animatedImage
+ * is set, override @c animatedImageSet:previousAnimatedImage:
  */
 @property (nullable, nonatomic, strong) id <ASAnimatedImageProtocol> animatedImage;
 
@@ -168,6 +171,15 @@ typedef UIImage * _Nullable (^asimagenode_modification_block_t)(UIImage *image);
  */
 @property (nonatomic, strong) NSString *animatedImageRunLoopMode;
 
+/**
+ * @abstract Method called when animated image has been set
+ *
+ * @discussion This method is for subclasses to override so they can know if an animated image
+ * has been set on the node.
+ * @warning this method is called with the node's lock held.
+ */
+- (void)animatedImageSet:(id <ASAnimatedImageProtocol>)newAnimatedImage previousAnimatedImage:(id <ASAnimatedImageProtocol>)previousAnimatedImage;
+
 @end
 
 @interface ASImageNode (Unavailable)

Source/ASMultiplexImageNode.mm

@@ -257,7 +257,7 @@ typedef void(^ASMultiplexImageLoadCompletionBlock)(UIImage *image, id imageIdent
 
 - (BOOL)placeholderShouldPersist
 {
-  return (self.image == nil && self.imageIdentifiers.count > 0);
+  return (self.image == nil && self.animatedImage == nil && self.imageIdentifiers.count > 0);
 }
 
 /* displayWillStart in ASNetworkImageNode has a very similar implementation. Changes here are likely necessary

Source/ASNetworkImageNode.mm

@@ -309,7 +309,7 @@ static const CGSize kMinReleaseImageOnBackgroundSize = {20.0, 20.0};
 - (BOOL)placeholderShouldPersist
 {
   ASDN::MutexLocker l(__instanceLock__);
-  return (self.image == nil && _URL != nil);
+  return (self.image == nil && self.animatedImage == nil && _URL != nil);
 }
 
 /* displayWillStart in ASMultiplexImageNode has a very similar implementation. Changes here are likely necessary