Swiftgram/AsyncDisplayKit/Private/ASPendingStateController.mm
2016-02-20 15:40:47 -08:00

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//
// ASPendingStateController.m
// AsyncDisplayKit
//
// Created by Adlai Holler on 1/7/16.
// Copyright © 2016 Facebook. All rights reserved.
//
#import "ASPendingStateController.h"
#import "ASThread.h"
#import "ASWeakSet.h"
#import "ASAssert.h"
#import "ASDisplayNodeInternal.h"
@interface ASPendingStateController()
{
ASDN::Mutex _lock;
struct ASPendingStateControllerFlags {
unsigned pendingFlush:1;
} _flags;
}
@property (nonatomic, strong, readonly) ASWeakSet<ASDisplayNode *> *dirtyNodes;
@end
@implementation ASPendingStateController
#pragma mark Lifecycle & Singleton
- (instancetype)init
{
self = [super init];
if (self) {
_dirtyNodes = [ASWeakSet new];
}
return self;
}
+ (ASPendingStateController *)sharedInstance
{
static dispatch_once_t onceToken;
static ASPendingStateController *controller;
dispatch_once(&onceToken, ^{
controller = [ASPendingStateController new];
});
return controller;
}
#pragma mark External API
- (void)flush
{
ASDisplayNodeAssertMainThread();
[self flushNow];
}
- (void)registerNode:(ASDisplayNode *)node
{
ASDisplayNodeAssert(node.nodeLoaded, @"Expected display node to be loaded before it was registered with ASPendingStateController. Node: %@", node);
ASDN::MutexLocker l(_lock);
[_dirtyNodes addObject:node];
[self scheduleFlushIfNeeded];
}
#pragma mark Private Methods
/**
This method is assumed to be called with the lock held.
*/
- (void)scheduleFlushIfNeeded
{
if (_flags.pendingFlush) {
return;
}
_flags.pendingFlush = YES;
dispatch_async(dispatch_get_main_queue(), ^{
[self flushNow];
});
}
/**
* NOTE: There is a small re-entrancy hazard here.
* If the user gives us a subclass of UIView/CALayer that
* adds side-effects to property sets, and one side effect
* waits on a background thread that sets a view/layer property
* on a loaded node, then we've got a deadlock.
*/
- (void)flushNow
{
ASDN::MutexLocker l(_lock);
for (ASDisplayNode *node in _dirtyNodes) {
[node applyPendingViewState];
}
[_dirtyNodes removeAllObjects];
_flags.pendingFlush = NO;
}
@end
@implementation ASPendingStateController (Testing)
- (BOOL)test_isFlushScheduled
{
return _flags.pendingFlush;
}
@end