ASDisplayNode+InterfaceState.h
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typedef NS_OPTIONS(NSUInteger, ASInterfaceState)
{
/** The element is not predicted to be onscreen soon and preloading should not be performed */
ASInterfaceStateNone = 0,
/** The element may be added to a view soon that could become visible. Measure the layout, including size calculation. */
ASInterfaceStateMeasureLayout = 1 << 0,
/** The element is likely enough to come onscreen that disk and/or network data required for display should be fetched. */
ASInterfaceStatePreload = 1 << 1,
/** The element is very likely to become visible, and concurrent rendering should be executed for any -setNeedsDisplay. */
ASInterfaceStateDisplay = 1 << 2,
/** The element is physically onscreen by at least 1 pixel.
In practice, all other bit fields should also be set when this flag is set. */
ASInterfaceStateVisible = 1 << 3,
/**
* The node is not contained in a cell but it is in a window.
*
* Currently we only set `interfaceState` to other values for
* nodes contained in table views or collection views.
*/
ASInterfaceStateInHierarchy = ASInterfaceStateMeasureLayout | ASInterfaceStatePreload | ASInterfaceStateDisplay | ASInterfaceStateVisible,
};
ASInterfaceStateDelegate
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@protocol ASInterfaceStateDelegate <NSObject>
/**
* @abstract Called whenever any bit in the ASInterfaceState bitfield is changed.
* @discussion Subclasses may use this to monitor when they become visible, should free cached data, and much more.
* @see ASInterfaceState
*/
- (void)interfaceStateDidChange:(ASInterfaceState)newState fromState:(ASInterfaceState)oldState;
/**
* @abstract Called whenever the node becomes visible.
* @discussion Subclasses may use this to monitor when they become visible.
* @note This method is guaranteed to be called on main.
*/
- (void)didEnterVisibleState;
/**
* @abstract Called whenever the node is no longer visible.
* @discussion Subclasses may use this to monitor when they are no longer visible.
* @note This method is guaranteed to be called on main.
*/
- (void)didExitVisibleState;
/**
* @abstract Called whenever the the node has entered the display state.
* @discussion Subclasses may use this to monitor when a node should be rendering its content.
* @note This method is guaranteed to be called on main.
*/
- (void)didEnterDisplayState;
/**
* @abstract Called whenever the the node has exited the display state.
* @discussion Subclasses may use this to monitor when a node should no longer be rendering its content.
* @note This method is guaranteed to be called on main.
*/
- (void)didExitDisplayState;
/**
* @abstract Called whenever the the node has entered the preload state.
* @discussion Subclasses may use this to monitor data for a node should be preloaded, either from a local or remote source.
* @note This method is guaranteed to be called on main.
*/
- (void)didEnterPreloadState;
/**
* @abstract Called whenever the the node has exited the preload state.
* @discussion Subclasses may use this to monitor whether preloading data for a node should be canceled.
* @note This method is guaranteed to be called on main.
*/
- (void)didExitPreloadState;
/**
* @abstract Called when the node has completed applying the layout.
* @discussion Can be used for operations that are performed after layout has completed.
* @note This method is guaranteed to be called on main.
*/
- (void)nodeDidLayout;
/**
* @abstract Called when the node loads.
* @discussion Can be used for operations that are performed after the node's view is available.
* @note This method is guaranteed to be called on main.
*/
- (void)nodeDidLoad;
/**
* @abstract Indicates that the receiver and all subnodes have finished displaying.
* @discussion May be called more than once, for example if the receiver has a network image node.
* This is called after the first display pass even if network image nodes have not downloaded anything
* (text would be done, and other nodes that are ready to do their final display). Each render of
* every progressive jpeg network node would cause this to be called, so this hook could be called up to
* 1 + (pJPEGcount * pJPEGrenderCount) times. The render count depends on how many times the downloader calls
* the progressImage block.
* @note This method is guaranteed to be called on main.
*/
- (void)hierarchyDisplayDidFinish;
@optional
/**
* @abstract Called when the node is about to calculate layout. This is only called before
* Yoga-driven layouts.
* @discussion Can be used for operations that are performed after the node's view is available.
* @note This method is guaranteed to be called on main, but implementations should be careful not
* to attempt to ascend the node tree when handling this, as the root node is locked when this is
* called.
*/
- (void)nodeWillCalculateLayout:(ASSizeRange)constrainedSize;
@end