//
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// YYTextAsyncLayer.h
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// YYText <https://github.com/ibireme/YYText>
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//
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// Created by ibireme on 15/4/11.
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// Copyright (c) 2015 ibireme.
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//
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// This source code is licensed under the MIT-style license found in the
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// LICENSE file in the root directory of this source tree.
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//
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#import <UIKit/UIKit.h>
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#import <QuartzCore/QuartzCore.h>
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@class YYTextAsyncLayerDisplayTask;
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NS_ASSUME_NONNULL_BEGIN
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/**
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The YYTextAsyncLayer class is a subclass of CALayer used for render contents asynchronously.
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@discussion When the layer need update it's contents, it will ask the delegate
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for a async display task to render the contents in a background queue.
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*/
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@interface YYTextAsyncLayer : CALayer
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/// Whether the render code is executed in background. Default is YES.
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@property BOOL displaysAsynchronously;
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@end
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/**
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The YYTextAsyncLayer's delegate protocol. The delegate of the YYTextAsyncLayer (typically a UIView)
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must implements the method in this protocol.
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*/
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@protocol YYTextAsyncLayerDelegate <NSObject>
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@required
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/// This method is called to return a new display task when the layer's contents need update.
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- (YYTextAsyncLayerDisplayTask *)newAsyncDisplayTask;
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@end
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/**
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A display task used by YYTextAsyncLayer to render the contents in background queue.
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*/
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@interface YYTextAsyncLayerDisplayTask : NSObject
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/**
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This block will be called before the asynchronous drawing begins.
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It will be called on the main thread.
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@param layer The layer.
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*/
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@property (nullable, nonatomic, copy) void (^willDisplay)(CALayer *layer);
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/**
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This block is called to draw the layer's contents.
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@discussion This block may be called on main thread or background thread,
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so is should be thread-safe.
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@param context A new bitmap content created by layer.
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@param size The content size (typically same as layer's bound size).
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@param isCancelled If this block returns `YES`, the method should cancel the
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drawing process and return as quickly as possible.
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*/
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@property (nullable, nonatomic, copy) void (^display)(CGContextRef context, CGSize size, BOOL(^isCancelled)(void));
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/**
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This block will be called after the asynchronous drawing finished.
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It will be called on the main thread.
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@param layer The layer.
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@param finished If the draw process is cancelled, it's `NO`, otherwise it's `YES`;
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*/
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@property (nullable, nonatomic, copy) void (^didDisplay)(CALayer *layer, BOOL finished);
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@end
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NS_ASSUME_NONNULL_END
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