基于 CoreText 的排版引擎：基础

#import "CTDisplayView.h"
#import "CoreText/CoreText.h"

@implementation CTDisplayView

- (void)drawRect:(CGRect)rect
{
    [super drawRect:rect];

    // 步骤 1
    CGContextRef context = UIGraphicsGetCurrentContext();

    // 步骤 2
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    CGContextTranslateCTM(context, 0, self.bounds.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    // 步骤 3
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, self.bounds);

    // 步骤 4
    NSAttributedString *attString = [[NSAttributedString alloc] initWithString:@"Hello World!"];
    CTFramesetterRef framesetter =
    CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attString);
    CTFrameRef frame =
    CTFramesetterCreateFrame(framesetter,
                             CFRangeMake(0, [attString length]), path, NULL);

    // 步骤 5
    CTFrameDraw(frame, context);

    // 步骤 6
    CFRelease(frame);
    CFRelease(path);
    CFRelease(framesetter);
}

@end

// 步骤 3
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddEllipseInRect(path, NULL, self.bounds);

// 步骤 4
NSAttributedString *attString = [[NSAttributedString alloc] initWithString:@"Hello World! "
                                 " 创建绘制的区域，CoreText 本身支持各种文字排版的区域，"
                                 " 我们这里简单地将 UIView 的整个界面作为排版的区域。"
                                 " 为了加深理解，建议读者将该步骤的代码替换成如下代码，"
                                 " 测试设置不同的绘制区域带来的界面变化。"];

#ifdef DEBUG
#define debugLog(...) NSLog(__VA_ARGS__)
#define debugMethod() NSLog(@"%s", __func__)
#else
#define debugLog(...)
#define debugMethod()
#endif

#define RGB(A, B, C)    [UIColor colorWithRed:A/255.0 green:B/255.0 blue:C/255.0 alpha:1.0]

#import <Foundation/Foundation.h>

@interface UIView (frameAdjust)

- (CGFloat)x;
- (void)setX:(CGFloat)x;

- (CGFloat)y;
- (void)setY:(CGFloat)y;

- (CGFloat)height;
- (void)setHeight:(CGFloat)height;

- (CGFloat)width;
- (void)setWidth:(CGFloat)width;

@end

@implementation UIView (frameAdjust)
- (CGFloat)x {
    return self.frame.origin.x;
}

- (void)setX:(CGFloat)x {
    self.frame = CGRectMake(x, self.y, self.width, self.height);
}

- (CGFloat)y {
    return self.frame.origin.y;
}

- (void)setY:(CGFloat)y {
    self.frame = CGRectMake(self.x, y, self.width, self.height);
}

- (CGFloat)height {
    return self.frame.size.height;
}
- (void)setHeight:(CGFloat)height {
    self.frame = CGRectMake(self.x, self.y, self.width, height);
}

- (CGFloat)width {
    return self.frame.size.width;
}
- (void)setWidth:(CGFloat)width {
    self.frame = CGRectMake(self.x, self.y, width, self.height);
}

@end

#import <Foundation/Foundation.h>
@interface CTFrameParserConfig : NSObject

@property (nonatomic, assign) CGFloat width;
@property (nonatomic, assign) CGFloat fontSize;
@property (nonatomic, assign) CGFloat lineSpace;
@property (nonatomic, strong) UIColor *textColor;

@end

#import "CTFrameParserConfig.h"

@implementation CTFrameParserConfig

- (id)init {
    self = [super init];
    if (self) {
        _width = 200.0f;
        _fontSize = 16.0f;
        _lineSpace = 8.0f;
        _textColor = RGB(108, 108, 108);
    }
    return self;
}

@end

#import <Foundation/Foundation.h>
#import "CoreTextData.h"
#import "CTFrameParserConfig.h"

@interface CTFrameParser : NSObject

+ (CoreTextData *)parseContent:(NSString *)content config:(CTFrameParserConfig*)config;

@end

#import "CTFrameParser.h"
#import "CTFrameParserConfig.h"

@implementation CTFrameParser

+ (NSDictionary *)attributesWithConfig:(CTFrameParserConfig *)config {
    CGFloat fontSize = config.fontSize;
    CTFontRef fontRef = CTFontCreateWithName((CFStringRef)@"ArialMT", fontSize, NULL);
    CGFloat lineSpacing = config.lineSpace;
    const CFIndex kNumberOfSettings = 3;
    CTParagraphStyleSetting theSettings[kNumberOfSettings] = {
        { kCTParagraphStyleSpecifierLineSpacingAdjustment, sizeof(CGFloat), &lineSpacing },
        { kCTParagraphStyleSpecifierMaximumLineSpacing, sizeof(CGFloat), &lineSpacing },
        { kCTParagraphStyleSpecifierMinimumLineSpacing, sizeof(CGFloat), &lineSpacing }
    };

    CTParagraphStyleRef theParagraphRef = CTParagraphStyleCreate(theSettings, kNumberOfSettings);

    UIColor * textColor = config.textColor;

    NSMutableDictionary * dict = [NSMutableDictionary dictionary];
    dict[(id)kCTForegroundColorAttributeName] = (id)textColor.CGColor;
    dict[(id)kCTFontAttributeName] = (__bridge id)fontRef;
    dict[(id)kCTParagraphStyleAttributeName] = (__bridge id)theParagraphRef;

    CFRelease(theParagraphRef);
    CFRelease(fontRef);
    return dict;
}

+ (CoreTextData *)parseContent:(NSString *)content config:(CTFrameParserConfig*)config {
    NSDictionary *attributes = [self attributesWithConfig:config];
    NSAttributedString *contentString =
        [[NSAttributedString alloc] initWithString:content
                                        attributes:attributes];

    // 创建 CTFramesetterRef 实例
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)contentString);

    // 获得要绘制的区域的高度
    CGSize restrictSize = CGSizeMake(config.width, CGFLOAT_MAX);
    CGSize coreTextSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter, CFRangeMake(0,0), nil, restrictSize, nil);
    CGFloat textHeight = coreTextSize.height;

    // 生成 CTFrameRef 实例
    CTFrameRef frame = [self createFrameWithFramesetter:framesetter config:config height:textHeight];

    // 将生成好的 CTFrameRef 实例和计算好的绘制高度保存到 CoreTextData 实例中，最后返回 CoreTextData 实例
    CoreTextData *data = [[CoreTextData alloc] init];
    data.ctFrame = frame;
    data.height = textHeight;

    // 释放内存
    CFRelease(frame);
    CFRelease(framesetter);
    return data;
}

+ (CTFrameRef)createFrameWithFramesetter:(CTFramesetterRef)framesetter
                                  config:(CTFrameParserConfig *)config
                                  height:(CGFloat)height {

    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, CGRectMake(0, 0, config.width, height));

    CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);
    CFRelease(path);
    return frame;
}

@end

#import <Foundation/Foundation.h>

@interface CoreTextData : NSObject

@property (assign, nonatomic) CTFrameRef ctFrame;
@property (assign, nonatomic) CGFloat height;

@end

#import "CoreTextData.h"

@implementation CoreTextData

- (void)setCtFrame:(CTFrameRef)ctFrame {
    if (_ctFrame != ctFrame) {
        if (_ctFrame != nil) {
            CFRelease(_ctFrame);
        }
        CFRetain(ctFrame);
        _ctFrame = ctFrame;
    }
}

- (void)dealloc {
    if (_ctFrame != nil) {
        CFRelease(_ctFrame);
        _ctFrame = nil;
    }
}

@end

#import <Foundation/Foundation.h>
#import "CoreTextData.h"

@interface CTDisplayView : UIView

@property (strong, nonatomic) CoreTextData * data;

@end

#import "CTDisplayView.h"

@implementation CTDisplayView

- (void)drawRect:(CGRect)rect
{
    [super drawRect:rect];
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    CGContextTranslateCTM(context, 0, self.bounds.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    if (self.data) {
        CTFrameDraw(self.data.ctFrame, context);
    }
}

@end

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath;

- (UITableViewCell *)cellForRowAtIndexPath:(NSIndexPath *)indexPath;

#import "ViewController.h"

@interface ViewController ()

@property (weak, nonatomic) IBOutlet CTDisplayView *ctView;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    CTFrameParserConfig *config = [[CTFrameParserConfig alloc] init];
    config.textColor = [UIColor redColor];
    config.width = self.ctView.width;

    CoreTextData *data = [CTFrameParser parseContent:@" 按照以上原则，我们将`CTDisplayView`中的部分内容拆开。" config:config];
    self.ctView.data = data;
    self.ctView.height = data.height;
    self.ctView.backgroundColor = [UIColor yellowColor];
}

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    CTFrameParserConfig *config = [[CTFrameParserConfig alloc] init];
    config.width = self.ctView.width;
    config.textColor = [UIColor blackColor];

    NSString *content =
        @" 对于上面的例子，我们给 CTFrameParser 增加了一个将 NSString 转 "
         " 换为 CoreTextData 的方法。"
         " 但这样的实现方式有很多局限性，因为整个内容虽然可以定制字体 "
         " 大小，颜色，行高等信息，但是却不能支持定制内容中的某一部分。"
         " 例如，如果我们只想让内容的前三个字显示成红色，而其它文字显 "
         " 示成黑色，那么就办不到了。"
         "\n\n"
         " 解决的办法很简单，我们让`CTFrameParser`支持接受 "
         "NSAttributeString 作为参数，然后在 NSAttributeString 中设置好 "
         " 我们想要的信息。";
    NSDictionary *attr = [CTFrameParser attributesWithConfig:config];
    NSMutableAttributedString *attributedString =
         [[NSMutableAttributedString alloc] initWithString:content
                                                attributes:attr];
    [attributedString addAttribute:NSForegroundColorAttributeName
                             value:[UIColor redColor]
                             range:NSMakeRange(0, 7)];

    CoreTextData *data = [CTFrameParser parseAttributedContent:attributedString
                                                        config:config];
    self.ctView.data = data;
    self.ctView.height = data.height;
    self.ctView.backgroundColor = [UIColor yellowColor];
}

@end

[ { "color" : "blue",
    "content" : " 更进一步地，实际工作中，我们更希望通过一个排版文件，来设置需要排版的文字的 ",
    "size" : 16,
    "type" : "txt"
  },
  { "color" : "red",
    "content" : " 内容、颜色、字体 ",
    "size" : 22,
    "type" : "txt"
  },
  { "color" : "black",
    "content" : " 大小等信息。\n",
    "size" : 16,
    "type" : "txt"
  },
  { "color" : "default",
    "content" : " 我在开发猿题库应用时，自己定义了一个基于 UBB 的排版模版，但是实现该排版文件的解析器要花费大量的篇幅，考虑到这并不是本章的重点，所以我们以一个较简单的排版文件来讲解其思想。",
    "type" : "txt"
  }
]

// 方法一
+ (CoreTextData *)parseTemplateFile:(NSString *)path config:(CTFrameParserConfig*)config {
    NSAttributedString *content = [self loadTemplateFile:path config:config];
    return [self parseAttributedContent:content config:config];
}

// 方法二
+ (NSAttributedString *)loadTemplateFile:(NSString *)path config:(CTFrameParserConfig*)config {
    NSData *data = [NSData dataWithContentsOfFile:path];
    NSMutableAttributedString *result = [[NSMutableAttributedString alloc] init];
    if (data) {
        NSArray *array = [NSJSONSerialization JSONObjectWithData:data
                                           options:NSJSONReadingAllowFragments
                                             error:nil];
        if ([array isKindOfClass:[NSArray class]]) {
            for (NSDictionary *dict in array) {
                NSString *type = dict[@"type"];
                if ([type isEqualToString:@"txt"]) {
                    NSAttributedString *as =
                       [self parseAttributedContentFromNSDictionary:dict
                                                             config:config];
                    [result appendAttributedString:as];
                }
            }
        }
    }
    return result;
}

// 方法三
+ (NSAttributedString *)parseAttributedContentFromNSDictionary:(NSDictionary *)dict
                                                        config:(CTFrameParserConfig*)config {
    NSMutableDictionary *attributes = [self attributesWithConfig:config];
    // set color
    UIColor *color = [self colorFromTemplate:dict[@"color"]];
    if (color) {
        attributes[(id)kCTForegroundColorAttributeName] = (id)color.CGColor;
    }
    // set font size
    CGFloat fontSize = [dict[@"size"] floatValue];
    if (fontSize > 0) {
        CTFontRef fontRef = CTFontCreateWithName((CFStringRef)@"ArialMT", fontSize, NULL);
        attributes[(id)kCTFontAttributeName] = (__bridge id)fontRef;
        CFRelease(fontRef);
    }
    NSString *content = dict[@"content"];
    return [[NSAttributedString alloc] initWithString:content attributes:attributes];
}

// 方法四
+ (UIColor *)colorFromTemplate:(NSString *)name {
    if ([name isEqualToString:@"blue"]) {
        return [UIColor blueColor];
    } else if ([name isEqualToString:@"red"]) {
        return [UIColor redColor];
    } else if ([name isEqualToString:@"black"]) {
        return [UIColor blackColor];
    } else {
        return nil;
    }
}

// 方法五
+ (CoreTextData *)parseAttributedContent:(NSAttributedString *)content config:(CTFrameParserConfig*)config {
    // 创建 CTFramesetterRef 实例
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)content);

    // 获得要缓制的区域的高度
    CGSize restrictSize = CGSizeMake(config.width, CGFLOAT_MAX);
    CGSize coreTextSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter, CFRangeMake(0,0), nil, restrictSize, nil);
    CGFloat textHeight = coreTextSize.height;

    // 生成 CTFrameRef 实例
    CTFrameRef frame = [self createFrameWithFramesetter:framesetter config:config height:textHeight];

    // 将生成好的 CTFrameRef 实例和计算好的缓制高度保存到 CoreTextData 实例中，最后返回 CoreTextData 实例
    CoreTextData *data = [[CoreTextData alloc] init];
    data.ctFrame = frame;
    data.height = textHeight;

    // 释放内存
    CFRelease(frame);
    CFRelease(framesetter);
    return data;
}

// 方法六
+ (CTFrameRef)createFrameWithFramesetter:(CTFramesetterRef)framesetter
                                  config:(CTFrameParserConfig *)config
                                  height:(CGFloat)height {

    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, CGRectMake(0, 0, config.width, height));

    CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);
    CFRelease(path);
    return frame;
}

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    CTFrameParserConfig *config = [[CTFrameParserConfig alloc] init];
    config.width = self.ctView.width;
    NSString *path = [[NSBundle mainBundle] pathForResource:@"content" ofType:@"json"];
    CoreTextData *data = [CTFrameParser parseTemplateFile:path config:config];
    self.ctView.data = data;
    self.ctView.height = data.height;
    self.ctView.backgroundColor = [UIColor whiteColor];
}

@end