NSAttributedString+CoreTextHelper.m

//
//  NSAttributedString+CoreTextHelper.m
//  TutorTeacherHD
//
//  Created by skyline on 16/8/8.
//  Copyright © 2016年 skyline. All rights reserved.
//

#import "NSAttributedString+CoreTextHelper.h"
#import <CoreText/CoreText.h>
#import <objc/runtime.h>

static char lastLineWidthCacheKey;
static char lineCountCacheKey;

@implementation NSAttributedString (CoreTextHelper)

- (NSMutableDictionary *)lastLineWidthCache {
    NSMutableDictionary *cache = objc_getAssociatedObject(self, &lastLineWidthCacheKey);
    if (cache) {
        return cache;
    }
    cache = [NSMutableDictionary dictionary];
    objc_setAssociatedObject(self, &lastLineWidthCacheKey, cache, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    return cache;
}

- (NSMutableDictionary *)lineCountCache {
    NSMutableDictionary *cache = objc_getAssociatedObject(self, &lineCountCacheKey);
    if (cache) {
        return cache;
    }
    cache = [NSMutableDictionary dictionary];
    objc_setAssociatedObject(self, &lineCountCacheKey, cache, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    return cache;
}

- (NSString *)cacheStoreKeyWithRect:(CGRect)rect {
    return [NSString stringWithFormat:@"%@_%@", self.string, NSStringFromCGRect(rect)];
}

- (CGFloat)lastLineWidthWithBoundingRect:(CGRect)rect {
    NSNumber *cachedValue = [self.lastLineWidthCache objectForKey:[self cacheStoreKeyWithRect:rect]];
    if (cachedValue) {
#if CGFLOAT_IS_DOUBLE
        return [cachedValue doubleValue];
#else
        return [cachedValue floatValue];
#endif
    }
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFMutableAttributedStringRef)self);
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, rect);
    CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);
    CFArrayRef lines = CTFrameGetLines(frame);

    NSInteger lineCount = CFArrayGetCount(lines);
    [self.lineCountCache setObject:@(lineCount) forKey:[self cacheStoreKeyWithRect:rect]];

    CTLineRef lastLine = CFArrayGetValueAtIndex(lines, MAX(lineCount - 1, 0));
    CGFloat ascent;
    CGFloat descent;
    CGFloat leading;
#if CGFLOAT_IS_DOUBLE
    double lineWidth = CTLineGetTypographicBounds(lastLine, &ascent, &descent, &leading);
#else
    CGFloat lineWidth = (CGFloat)CTLineGetTypographicBounds(lastLine, &ascent, &descent, &leading);
#endif
    [self.lastLineWidthCache setObject:@(lineWidth) forKey:[self cacheStoreKeyWithRect:rect]];

    CFRelease(path);
    CFRelease(frame);
    CFRelease(framesetter);
    return lineWidth;
}

- (NSInteger)lineCountWithBoundingRect:(CGRect)rect {
    NSNumber *cachedValue = [self.lineCountCache objectForKey:[self cacheStoreKeyWithRect:rect]];
    if (cachedValue) {
        return [cachedValue integerValue];
    }
    return -1;
}

@end