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a58844379c
This provides internal features on _ASAsyncTransaction and ASDisplayNode to facilitate implementing public API that allows clients to choose if they would prefer to block on the completion of unfinished rendering, rather than allow a placeholder state to become visible. The internal features are: -[_ASAsyncTransaction waitUntilComplete] -[ASDisplayNode recursivelyEnsureDisplay] Also provided are two such implementations: -[ASCellNode setNeverShowPlaceholders:], which integrates with both Tables and Collections -[ASViewController setNeverShowPlaceholders:], which should work with Nav and Tab controllers. Lastly, on ASDisplayNode, a new property .shouldBypassEnsureDisplay allows individual node types to exempt themselves from blocking the main thread on their display. By implementing the feature at the ASCellNode level rather than ASTableView & ASCollectionView, developers can retain fine-grained control on display characteristics. For example, certain cell types may be appropriate to display to the user with placeholders, whereas others may not. Follow-up work will include unit tests, revisiting names, and the header locations of definitions.
69 lines
2.8 KiB
Objective-C
69 lines
2.8 KiB
Objective-C
/* Copyright (c) 2014-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*/
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#import <AsyncDisplayKit/ASDisplayNode.h>
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/**
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* Generic cell node. Subclass this instead of `ASDisplayNode` to use with `ASTableView` and `ASCollectionView`.
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*/
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@interface ASCellNode : ASDisplayNode
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/**
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* @abstract When enabled, ensures that the cell is completely displayed before allowed onscreen.
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*
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* @default NO
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* @discussion Normally, ASCellNodes are preloaded and have finished display before they are onscreen.
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* However, if the Table or Collection's rangeTuningParameters are set to small values (or 0),
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* or if the user is scrolling rapidly on a slow device, it is possible for a cell's display to
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* be incomplete when it becomes visible.
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*
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* In this case, normally placeholder states are shown and scrolling continues uninterrupted.
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* The finished, drawn content is then shown as soon as it is ready.
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*
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* With this property set to YES, the main thread will be blocked until display is complete for
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* the cell. This is more similar to UIKit, and in fact makes AsyncDisplayKit scrolling visually
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* indistinguishible from UIKit's, except being faster.
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*
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* Using this option does not eliminate all of the performance advantages of AsyncDisplayKit.
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* Normally, a cell has been preloading and is almost done when it reaches the screen, so the
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* blocking time is very short. If the rangeTuningParameters are set to 0, still this option
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* outperforms UIKit: while the main thread is waiting, subnode display executes concurrently.
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*/
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@property (nonatomic, assign) BOOL neverShowPlaceholders;
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/*
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* ASTableView uses these properties when configuring UITableViewCells that host ASCellNodes.
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*/
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//@property (atomic, retain) UIColor *backgroundColor;
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@property (nonatomic) UITableViewCellSelectionStyle selectionStyle;
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/*
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* ASCellNode must forward touch events in order for UITableView and UICollectionView tap handling to work. Overriding
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* these methods (e.g. for highlighting) requires the super method be called.
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*/
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- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event ASDISPLAYNODE_REQUIRES_SUPER;
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- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event ASDISPLAYNODE_REQUIRES_SUPER;
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- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event ASDISPLAYNODE_REQUIRES_SUPER;
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- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event ASDISPLAYNODE_REQUIRES_SUPER;
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@end
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/**
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* Simple label-style cell node. Read its source for an example of custom <ASCellNode>s.
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*/
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@interface ASTextCellNode : ASCellNode
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/**
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* Text to display.
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*/
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@property (nonatomic, copy) NSString *text;
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@end
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