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//
// ASMultiplexImageNode.h
// AsyncDisplayKit
//
// Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
#import <AsyncDisplayKit/ASImageNode.h>
#import <AsyncDisplayKit/ASImageProtocols.h>
#import <Photos/Photos.h>
NS_ASSUME_NONNULL_BEGIN
@protocol ASMultiplexImageNodeDelegate;
@protocol ASMultiplexImageNodeDataSource;
typedef id<NSCopying, NSObject> ASImageIdentifier;
extern NSString *const ASMultiplexImageNodeErrorDomain;
/**
* ASMultiplexImageNode error codes.
*/
typedef NS_ENUM(NSUInteger, ASMultiplexImageNodeErrorCode) {
/**
* Indicates that the data source didn't provide a source for an image identifier.
*/
ASMultiplexImageNodeErrorCodeNoSourceForImage = 0,
/**
* Indicates that the best image identifier changed before a download for a worse identifier began.
*/
ASMultiplexImageNodeErrorCodeBestImageIdentifierChanged,
/**
* Indicates that the Photos framework returned no image and no error.
* This may happen if the image is in iCloud and the user did not specify `allowsNetworkAccess`
* in their image request.
*/
ASMultiplexImageNodeErrorCodePhotosImageManagerFailedWithoutError,
/**
* Indicates that the image node could not retrieve the PHAsset for a given asset identifier.
* This typically means that the user has not given Photos framework permissions yet or the asset
* has been removed from the device.
*/
ASMultiplexImageNodeErrorCodePHAssetIsUnavailable
};
/**
* @abstract ASMultiplexImageNode is an image node that can load and display multiple versions of an image. For
* example, it can display a low-resolution version of an image while the high-resolution version is loading.
*
* @discussion ASMultiplexImageNode begins loading images when its resource can either return a UIImage directly, or a URL the image node should load.
*/
@interface ASMultiplexImageNode : ASImageNode
/**
* @abstract The designated initializer.
* @param cache The object that implements a cache of images for the image node.
* @param downloader The object that implements image downloading for the image node.
* @discussion If `cache` is nil, the receiver will not attempt to retrieve images from a cache before downloading them.
* @return An initialized ASMultiplexImageNode.
*/
- (instancetype)initWithCache:(nullable id<ASImageCacheProtocol>)cache downloader:(nullable id<ASImageDownloaderProtocol>)downloader NS_DESIGNATED_INITIALIZER;
/**
* @abstract The delegate, which must conform to the <ASMultiplexImageNodeDelegate> protocol.
*/
@property (nonatomic, readwrite, weak) id <ASMultiplexImageNodeDelegate> delegate;
/**
* @abstract The data source, which must conform to the <ASMultiplexImageNodeDataSource> protocol.
* @discussion This value is required for ASMultiplexImageNode to load images.
*/
@property (nonatomic, readwrite, weak) id <ASMultiplexImageNodeDataSource> dataSource;
/**
* @abstract Whether the receiver should download more than just its highest-quality image. Defaults to NO.
*
* @discussion ASMultiplexImageNode immediately loads and displays the first image specified in <imageIdentifiers> (its
* highest-quality image). If that image is not immediately available or cached, the node can download and display
* lesser-quality images. Set `downloadsIntermediateImages` to YES to enable this behaviour.
*/
@property (nonatomic, readwrite, assign) BOOL downloadsIntermediateImages;
/**
* @abstract An array of identifiers representing various versions of an image for ASMultiplexImageNode to display.
*
* @discussion An identifier can be any object that conforms to NSObject and NSCopying. The array should be in
* decreasing order of image quality -- that is, the first identifier in the array represents the best version.
*
* @see <downloadsIntermediateImages> for more information on the image loading process.
*/
@property (nonatomic, readwrite, copy) NSArray<ASImageIdentifier> *imageIdentifiers;
/**
* @abstract Notify the receiver SSAA that its data source has new UIImages or NSURLs available for <imageIdentifiers>.
*
* @discussion If a higher-quality image than is currently displayed is now available, it will be loaded.
*/
- (void)reloadImageIdentifierSources;
/**
* @abstract The identifier for the last image that the receiver loaded, or nil.
*
* @discussion This value may differ from <displayedImageIdentifier> if the image hasn't yet been displayed.
*/
@property (nullable, nonatomic, readonly) ASImageIdentifier loadedImageIdentifier;
/**
* @abstract The identifier for the image that the receiver is currently displaying, or nil.
*/
@property (nullable, nonatomic, readonly) ASImageIdentifier displayedImageIdentifier;
/**
* @abstract If the downloader implements progressive image rendering and this value is YES progressive renders of the
* image will be displayed as the image downloads. Regardless of this properties value, progress renders will
* only occur when the node is visible. Defaults to YES.
*/
@property (nonatomic, assign, readwrite) BOOL shouldRenderProgressImages;
#if TARGET_OS_IOS
/**
* @abstract The image manager that this image node should use when requesting images from the Photos framework. If this is `nil` (the default), then `PHImageManager.defaultManager` is used.
* @see `+[NSURL URLWithAssetLocalIdentifier:targetSize:contentMode:options:]` below.
*/
@property (nullable, nonatomic, strong) PHImageManager *imageManager;
#endif
@end
#pragma mark -
/**
* The methods declared by the ASMultiplexImageNodeDelegate protocol allow the adopting delegate to respond to
* notifications such as began, progressed and finished downloading, updated and displayed an image.
*/
@protocol ASMultiplexImageNodeDelegate <NSObject>
@optional
/**
* @abstract Notification that the image node began downloading an image.
* @param imageNode The sender.
* @param imageIdentifier The identifier for the image that is downloading.
*/
- (void)multiplexImageNode:(ASMultiplexImageNode *)imageNode didStartDownloadOfImageWithIdentifier:(id)imageIdentifier;
/**
* @abstract Notification that the image node's download progressed.
* @param imageNode The sender.
* @param downloadProgress The progress of the download. Value is between 0.0 and 1.0.
* @param imageIdentifier The identifier for the image that is downloading.
*/
- (void)multiplexImageNode:(ASMultiplexImageNode *)imageNode
didUpdateDownloadProgress:(CGFloat)downloadProgress
forImageWithIdentifier:(ASImageIdentifier)imageIdentifier;
/**
* @abstract Notification that the image node's download has finished.
* @param imageNode The sender.
* @param imageIdentifier The identifier for the image that finished downloading.
* @param error The error that occurred while downloading, if one occurred; nil otherwise.
*/
- (void)multiplexImageNode:(ASMultiplexImageNode *)imageNode
didFinishDownloadingImageWithIdentifier:(ASImageIdentifier)imageIdentifier
error:(nullable NSError *)error;
/**
* @abstract Notification that the image node's image was updated.
* @param imageNode The sender.
* @param image The new image, ready for display.
* @param imageIdentifier The identifier for `image`.
* @param previousImage The old, previously-loaded image.
* @param previousImageIdentifier The identifier for `previousImage`.
* @note This method does not indicate that `image` has been displayed.
* @see <[ASMultiplexImageNodeDelegate multiplexImageNode:didDisplayUpdatedImage:withIdentifier:]>.
*/
- (void)multiplexImageNode:(ASMultiplexImageNode *)imageNode
didUpdateImage:(nullable UIImage *)image
withIdentifier:(nullable ASImageIdentifier)imageIdentifier
fromImage:(nullable UIImage *)previousImage
withIdentifier:(nullable ASImageIdentifier)previousImageIdentifier;
/**
* @abstract Notification that the image node displayed a new image.
* @param imageNode The sender.
* @param image The new image, now being displayed.
* @param imageIdentifier The identifier for `image`.
* @discussion This method is only called when `image` changes, and not on subsequent redisplays of the same image.
*/
- (void)multiplexImageNode:(ASMultiplexImageNode *)imageNode
didDisplayUpdatedImage:(nullable UIImage *)image
withIdentifier:(nullable ASImageIdentifier)imageIdentifier;
/**
* @abstract Notification that the image node finished displaying an image.
* @param imageNode The sender.
* @discussion This method is called every time an image is displayed, whether or not it has changed.
*/
- (void)multiplexImageNodeDidFinishDisplay:(ASMultiplexImageNode *)imageNode;
@end
#pragma mark -
/**
* The ASMultiplexImageNodeDataSource protocol is adopted by an object that provides the multiplex image node,
* for each image identifier, an image or a URL the image node should load.
*/
@protocol ASMultiplexImageNodeDataSource <NSObject>
@optional
/**
* @abstract An image for the specified identifier.
* @param imageNode The sender.
* @param imageIdentifier The identifier for the image that should be returned.
* @discussion If the image is already available to the data source, this method should be used in lieu of providing the
* URL to the image via -multiplexImageNode:URLForImageIdentifier:.
* @return A UIImage corresponding to `imageIdentifier`, or nil if none is available.
*/
- (nullable UIImage *)multiplexImageNode:(ASMultiplexImageNode *)imageNode imageForImageIdentifier:(ASImageIdentifier)imageIdentifier;
/**
* @abstract An image URL for the specified identifier.
* @param imageNode The sender.
* @param imageIdentifier The identifier for the image that will be downloaded.
* @discussion Supported URLs include HTTP, HTTPS, AssetsLibrary, and FTP URLs as well as Photos framework URLs (see note).
*
* If the image is already available to the data source, it should be provided via <[ASMultiplexImageNodeDataSource
* multiplexImageNode:imageForImageIdentifier:]> instead.
* @return An NSURL for the image identified by `imageIdentifier`, or nil if none is available.
* @see `+[NSURL URLWithAssetLocalIdentifier:targetSize:contentMode:options:]` below.
*/
- (nullable NSURL *)multiplexImageNode:(ASMultiplexImageNode *)imageNode URLForImageIdentifier:(ASImageIdentifier)imageIdentifier;
#if TARGET_OS_IOS
/**
* @abstract A PHAsset for the specific asset local identifier
* @param imageNode The sender.
* @param assetLocalIdentifier The local identifier for a PHAsset that this image node is loading.
*
* @discussion This optional method can improve image performance if your data source already has the PHAsset available.
* If this method is not implemented, or returns nil, the image node will request the asset from the Photos framework.
* @note This method may be called from any thread.
* @return A PHAsset corresponding to `assetLocalIdentifier`, or nil if none is available.
*/
- (nullable PHAsset *)multiplexImageNode:(ASMultiplexImageNode *)imageNode assetForLocalIdentifier:(NSString *)assetLocalIdentifier;
#endif
@end
#pragma mark -
#if TARGET_OS_IOS
@interface NSURL (ASPhotosFrameworkURLs)
/**
* @abstract Create an NSURL that specifies an image from the Photos framework.
*
* @discussion When implementing `-multiplexImageNode:URLForImageIdentifier:`, you can return a URL
* created by this method and the image node will attempt to load the image from the Photos framework.
* @note The `synchronous` flag in `options` is ignored.
* @note The `Opportunistic` delivery mode is not supported and will be treated as `HighQualityFormat`.
*/
+ (NSURL *)URLWithAssetLocalIdentifier:(NSString *)assetLocalIdentifier
targetSize:(CGSize)targetSize
contentMode:(PHImageContentMode)contentMode
options:(PHImageRequestOptions *)options AS_WARN_UNUSED_RESULT;
@end
#endif
NS_ASSUME_NONNULL_END
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