#import "ViewController.h"
@interface ViewController ()
@property (nonatomic, strong) CADisplayLink *link;
@property (nonatomic, assign) NSTimeInterval lastTime;  // 每隔1秒記錄一次時間
@property (nonatomic, assign) NSUInteger count;         // 記錄VSync1秒內(nèi)發(fā)送的數(shù)量
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    self.link = [CADisplayLink displayLinkWithTarget:self selector:@selector(linkAction:)];
    [_link addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
}
- (void)linkAction: (CADisplayLink *)link {
    if (_lastTime == 0) {
        _lastTime = link.timestamp;
        return;
    }
    _count++;
    NSTimeInterval delta = link.timestamp - _lastTime;
    if (delta < 1) return;
    _lastTime = link.timestamp;
    float fps = _count / delta;
    _count = 0;
    NSLog(@"?? FPS : %f ", fps);
}
@end

#import "LZBlockMonitor.h"
@interface LZBlockMonitor (){
    CFRunLoopActivity activity;
}
@property (nonatomic, strong) dispatch_semaphore_t semaphore;
@property (nonatomic, assign) NSUInteger timeoutCount;
@end
@implementation LZBlockMonitor
+ (instancetype)sharedInstance {
    static id instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[self alloc] init];
    });
    return instance;
}
- (void)start{
    [self registerObserver];
    [self startMonitor];
}
- (void)registerObserver{
    CFRunLoopObserverContext context = {0, (__bridge void*)self, NULL, NULL};
    //NSIntegerMax : 優(yōu)先級最小
    CFRunLoopObserverRef observer = CFRunLoopObserverCreate(kCFAllocatorDefault,
                                                            kCFRunLoopAllActivities,
                                                            YES,
                                                            NSIntegerMax,
                                                            &CallBack,
                                                            &context);
    CFRunLoopAddObserver(CFRunLoopGetMain(), observer, kCFRunLoopCommonModes);
}
static void CallBack(CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info)
{
    LZBlockMonitor *monitor = (__bridge LZBlockMonitor *)info;
    monitor->activity = activity;
    // 發(fā)送信號
    dispatch_semaphore_t semaphore = monitor->_semaphore;
    dispatch_semaphore_signal(semaphore);
}
- (void)startMonitor{
    // 創(chuàng)建信號
    _semaphore = dispatch_semaphore_create(0);
    // 在子線程監(jiān)控時長
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        while (YES)
        {
            // 超時時間是 1 秒，沒有等到信號量，st 就不等于 0， RunLoop 所有的任務(wù)
            long st = dispatch_semaphore_wait(self->_semaphore, dispatch_time(DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC));
            if (st != 0)
            {
                if (self->activity == kCFRunLoopBeforeSources || self->activity == kCFRunLoopAfterWaiting)
                {
                    if (++self->_timeoutCount < 2){
                        NSLog(@"timeoutCount==%lu",(unsigned long)self->_timeoutCount);
                        continue;
                    }
                    // 一秒左右的衡量尺度 很大可能性連續(xù)來 避免大規(guī)模打印!
                    NSLog(@"檢測到超過兩次連續(xù)卡頓");
                }
            }
            self->_timeoutCount = 0;
        }
    });
}
@end

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
    [needLoadArr removeAllObjects];
}
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset{
    NSIndexPath *ip = [self indexPathForRowAtPoint:CGPointMake(0, targetContentOffset->y)];
    NSIndexPath *cip = [[self indexPathsForVisibleRows] firstObject];
    NSInteger skipCount = 8;
    if (labs(cip.row-ip.row)>skipCount) {
        NSArray *temp = [self indexPathsForRowsInRect:CGRectMake(0, targetContentOffset->y, self.width, self.height)];
        NSMutableArray *arr = [NSMutableArray arrayWithArray:temp];
        if (velocity.y<0) {
            NSIndexPath *indexPath = [temp lastObject];
            if (indexPath.row+3<datas.count) {
                [arr addObject:[NSIndexPath indexPathForRow:indexPath.row+1 inSection:0]];
                [arr addObject:[NSIndexPath indexPathForRow:indexPath.row+2 inSection:0]];
                [arr addObject:[NSIndexPath indexPathForRow:indexPath.row+3 inSection:0]];
            }
        } else {
            NSIndexPath *indexPath = [temp firstObject];
            if (indexPath.row>3) {
                [arr addObject:[NSIndexPath indexPathForRow:indexPath.row-3 inSection:0]];
                [arr addObject:[NSIndexPath indexPathForRow:indexPath.row-2 inSection:0]];
                [arr addObject:[NSIndexPath indexPathForRow:indexPath.row-1 inSection:0]];
            }
        }
        [needLoadArr addObjectsFromArray:arr];
    }
}

- (BOOL)scrollViewShouldScrollToTop:(UIScrollView *)scrollView{
    scrollToToping = YES;
    return YES;
}
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView{
    scrollToToping = NO;
    [self loadContent];
}
- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView{
    scrollToToping = NO;
    [self loadContent];
}
//用戶觸摸時第一時間加載內(nèi)容
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event{
    if (!scrollToToping) {
        [needLoadArr removeAllObjects];
        [self loadContent];
    }
    return [super hitTest:point withEvent:event];
}
- (void)loadContent{
    if (scrollToToping) {
        return;
    }
    if (self.indexPathsForVisibleRows.count<=0) {
        return;
    }
    if (self.visibleCells && self.visibleCells.count>0) {
        for (id temp in [self.visibleCells copy]) {
            VVeboTableViewCell *cell = (VVeboTableViewCell *)temp;
            [cell draw];
        }
    }
}

#import "LZLayer.h"
@implementation LZLayer
//前面斷點調(diào)用寫下的代碼
- (void)layoutSublayers{
    if (self.delegate && [self.delegate respondsToSelector:@selector(layoutSublayersOfLayer:)]) {
        //UIView
        [self.delegate layoutSublayersOfLayer:self];
    }else{
        [super layoutSublayers];
    }
}
//繪制流程的發(fā)起函數(shù)
- (void)display{
    // Graver 實現(xiàn)思路
    CGContextRef context = (__bridge CGContextRef)([self.delegate performSelector:@selector(createContext)]);
    [self.delegate layerWillDraw:self];
    [self drawInContext:context];
    [self.delegate displayLayer:self];
    [self.delegate performSelector:@selector(closeContext)];
}
@end

// - (CGContextRef)createContext 和 - (void)closeContext要在.h中聲明
#import "LZView.h"
#import "LZLayer.h"
@implementation LZView
- (void)drawRect:(CGRect)rect {
    // Drawing code， 繪制的操作， BackingStore(額外的存儲區(qū)域產(chǎn)于的) -- GPU
}
//子視圖的布局
- (void)layoutSubviews{
    [super layoutSubviews];
}
+ (Class)layerClass{
    return [LZLayer class];
}
//
- (void)layoutSublayersOfLayer:(CALayer *)layer{
    [super layoutSublayersOfLayer:layer];
    [self layoutSubviews];
}
- (CGContextRef)createContext{
    UIGraphicsBeginImageContextWithOptions(self.bounds.size, self.layer.opaque, self.layer.contentsScale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    return context;
}
- (void)layerWillDraw:(CALayer *)layer{
    //繪制的準(zhǔn)備工作,do nontihing
}
//繪制的操作
- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx{
    [super drawLayer:layer inContext:ctx];
    // 畫個不規(guī)則圖形
    CGContextMoveToPoint(ctx, self.bounds.size.width / 2- 20, 20);
    CGContextAddLineToPoint(ctx, self.bounds.size.width / 2 + 20, 20);
    CGContextAddLineToPoint(ctx, self.bounds.size.width / 2 + 40, 80);
    CGContextAddLineToPoint(ctx, self.bounds.size.width / 2 - 40, 100);
    CGContextAddLineToPoint(ctx, self.bounds.size.width / 2 - 20, 20);
    CGContextSetFillColorWithColor(ctx, UIColor.magentaColor.CGColor);
    CGContextSetStrokeColorWithColor(ctx, UIColor.magentaColor.CGColor); // 描邊
    CGContextDrawPath(ctx, kCGPathFillStroke);
    // 畫個紅色方塊
    [[UIColor redColor] set];
       //Core Graphics
    UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(self.bounds.size.width / 2- 20, self.bounds.size.height / 2- 20, 40, 40)];
    CGContextAddPath(ctx, path.CGPath);
    CGContextFillPath(ctx);
    // 文字
    [@"LZ" drawInRect:CGRectMake(self.bounds.size.width / 2 - 40, 100, 80, 24) withAttributes:@{NSFontAttributeName: [UIFont systemFontOfSize:20],NSForegroundColorAttributeName: UIColor.blueColor}];
    // 圖片
    [[UIImage imageWithContentsOfFile:@"/Volumes/Disk_D/test code/Test/Test/yasuo.png"] drawInRect:CGRectMake(10, self.bounds.size.height/2, self.bounds.size.width  - 20, self.bounds.size.height/2 -10)];
}
//layer.contents = (位圖)
- (void)displayLayer:(CALayer *)layer{
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    dispatch_async(dispatch_get_main_queue(), ^{
        layer.contents = (__bridge id)(image.CGImage);
    });
}
- (void)closeContext{
    UIGraphicsEndImageContext();
}