coretext简单使用

相对于UIKit，使用coretext绘制文本效率高，具有更高的自由度，可随时插入图片，增加文本点击事件等。

1.增加文本的点击事件

思路：定义UILabel子类，设置可点击的富文本range及其他属性（颜色、字体），touchBegin方法中根据点击位置判断所在行所在index，最后判断index是否在range内，若在，则响应事件。

　　首先定义可点击的文本model，该model主要含有3个属性，string-用于回调显示，range-用于判断位置，attributes-用于绘制文本

class LinkAttributesModel:NSObject {
    var string:String!
    var range:NSRange!
    var attributes:Dictionary<NSAttributedStringKey,Any>!
}

 　　接着在label子类实现方法setString(string:String,attributes:Dictionary<NSAttributedStringKey,Any>?,linkArr:Array<LinkAttributesModel>)，第一个参数是显示string，第二个参数是string的属性，第三个参数是一个可点击文本的集合，需要手动赋值

// 声明
func setString(string:String,attributes:Dictionary<NSAttributedStringKey,Any>?,linkArr:Array<LinkAttributesModel>) {
        locLinkArr = linkArr;
        let attributedString = NSMutableAttributedString(string: string, attributes: attributes)
        for linkMdl in linkArr {
            attributedString.addAttributes(linkMdl.attributes, range: linkMdl.range)
        }
//        self.attributedText = attributedString
        tmpAttributedString = attributedString
        
        // create frameRef
        let frameSetter = CTFramesetterCreateWithAttributedString(attributedString)
        let path = CGMutablePath()
        path.addRect(self.bounds)
        frameRef = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, string.count), path, nil)
        
        self.isUserInteractionEnabled = true
    }

// 调用
// 构造属性model
        var mdlArr = [LinkAttributesModel]()
        for i in 0...2 {
            let mdl = LinkAttributesModel()
            let loc = i*10
            let range = NSMakeRange(loc, 5)
            mdl.range = range
            let startIdx = showString.index(showString.startIndex, offsetBy: range.location)
            let endIdx = showString.index(startIdx, offsetBy: range.length)
            mdl.string = String(showString[startIdx...endIdx])
            let randomColor = UIColor(red: CGFloat(arc4random_uniform(256))/255.0, green: CGFloat(arc4random_uniform(256))/255.0, blue: CGFloat(arc4random_uniform(256))/255.0, alpha: 1)
            mdl.attributes = [NSAttributedStringKey.foregroundColor:randomColor]
            mdlArr.append(mdl)
        }
        
        let lbl = Taplabel(frame:self.view.bounds.insetBy(dx: 0, dy: 50))
        let style = NSMutableParagraphStyle()
        style.lineSpacing = 10
        lbl.setString(string: showString, attributes: [NSAttributedStringKey.font:UIFont.systemFont(ofSize: 20),NSAttributedStringKey.paragraphStyle:style], linkArr: mdlArr)

 　　最后根据属性文本创建对应的frameRef，然后遍历其CTLine数组，判断点击的位置在哪行内，再根据x获取当前行的偏移位置index，最后遍历linkAttributesModel，判断range是否包含index，如果包含，则触发回调事件

func touchEvents(pt:CGPoint) {
        if (frameRef == nil) {return}
        let lines:[CTLine] = CTFrameGetLines(frameRef!) as! [CTLine]
        let lineCount = lines.count
        if (lineCount == 0) {return}
//        let flipTransform = CGAffineTransform(translationX: 0, y: self.bounds.size.height).scaledBy(x: 1, y: -1)
        for i in 0..<lineCount {
            let line = lines[i]//CFArrayGetValueAtIndex(lines, i) as! CTLine
            var ascent:CGFloat = 0
            var descent:CGFloat = 0
            var leading:CGFloat = 0
            let width =  CGFloat(CTLineGetTypographicBounds(line, &ascent, &descent, &leading))
            let height = ascent + abs(descent) + leading
            
            var rect = CGRect(x: pt.x, y: pt.y,  width, height: height)
//            var rect = flippedRect.applying(flipTransform)
            
            var lineSpace:CGFloat = 0;
            if let style = tmpAttributedString?.attribute(NSAttributedStringKey.paragraphStyle, at: 0, effectiveRange: nil) as? NSParagraphStyle{
                lineSpace = style.lineSpacing
            }
            
            rect.origin.y = (height+lineSpace)*CGFloat(i);
            
            if rect.contains(pt) {
                var stringIndex = CTLineGetStringIndexForPosition(line, pt)
                var offset:CGFloat = 0
                CTLineGetOffsetForStringIndex(line, stringIndex, &offset)
                if (offset > pt.x) {
                    stringIndex = stringIndex - 1
                }
                
                for linkMdl in locLinkArr! {
                    if linkMdl.range.contains(stringIndex) {
                        tapBlock!(linkMdl.string)
                    }
                }
            }
        }
    }

 　　上述代码的主要核心在于

　　 a.算行高　　CTLineGetTypographicBounds(line,&asent,&descent,&leading)

　　 b.算行内偏移　　CTLineGetStringIndexForPosition(line,pt)　　如果根据该index算出的偏移量大于pt.x，则index-1

　　 c.判断range包含　　range.contains(index)

2.图文绘制

思路：NSAttributedString中插入占位空白符-关联图片属性。图片宽高由CTRunDelegate，图片可藏于追加属性中。ctx.draw(image,in:drawRect)时遍历CTLine，寻找含有CTRunDelegate的CTRun，如果存在，则获取图片的相应数组，构造drawRect和image绘制图片。

　　追加图片属性

func appendImage(attrStr:NSAttributedString)->NSAttributedString {
        var callBacks = CTRunDelegateCallbacks(version: kCTRunDelegateVersion1, dealloc: { (pointer) in
        }, getAscent: { (ref) -> CGFloat in
            let dic = ref.assumingMemoryBound(to: NSDictionary.self)
            return dic.pointee.object(forKey: "height") as! CGFloat
        }, getDescent: { (ref) -> CGFloat in
            return 0
        }) { (ref) -> CGFloat in
            let dic = ref.assumingMemoryBound(to: NSDictionary.self)
            return dic.pointee.object(forKey: "width") as! CGFloat
        }
        
        let imageData:Dictionary<String,Any> = ["height":100,"width":200]
        let imageDataPointer = UnsafeMutablePointer<Dictionary<String,Any>>.allocate(capacity: 1)
        imageDataPointer.initialize(to: imageData)
        let runDelegate = CTRunDelegateCreate(&callBacks, imageDataPointer)
        
        let runAttributes:[NSAttributedStringKey:Any] = [kCTRunDelegateAttributeName as NSAttributedStringKey:runDelegate as Any]
        let runAttributeStr = NSMutableAttributedString(string: " ", attributes: runAttributes)
        runAttributeStr.addAttribute(NSAttributedStringKey(rawValue: "imageName"), value: "shot", range: NSMakeRange(0, 1))
        
        let mutableAttrStr = NSMutableAttributedString(attributedString: attrStr)
        let whiteSpaceStr = createAttributedString(str: "临时换行
")
        let suffixStr = createAttributedString(str: "
haha insert image succeed")
        mutableAttrStr.append(whiteSpaceStr)
        mutableAttrStr.append(runAttributeStr)
        mutableAttrStr.append(suffixStr)
        return mutableAttrStr
    }

 　　绘制追加的图片属性

func drawImage(frame:CTFrame,ctx:CGContext) {
        let lines = CTFrameGetLines(frame) as Array
        var lineOrigins:Array<CGPoint> = Array(repeating: .zero, count: lines.count)
        CTFrameGetLineOrigins(frame, CFRange(location: 0, length: 0), &lineOrigins)
        for i in 0..<lines.count {
            let line = lines[i] as! CTLine
            let runs = CTLineGetGlyphRuns(line) as Array
            print("lineCount == (lines.count)  i == (i)
")
            for j in 0..<runs.count {
                let run = runs[j] as! CTRun
                let runAttribute = CTRunGetAttributes(run) as NSDictionary
//                if runAttribute == nil {return}
                print("runCount == (runs.count)    j == (j) runattribute == (runAttribute)")
                let runDelegate = runAttribute.object(forKey: kCTRunDelegateAttributeName as String)
                if (runDelegate == nil) {continue}
                var ascent:CGFloat = 0
                var descent:CGFloat = 0
                let CGFloat = CGFloat(CTRunGetTypographicBounds(run, CFRange(location: 0, length: 0), &ascent, &descent, nil))
                let xoffset = lineOrigins[i].x + CTLineGetOffsetForStringIndex(line, CTRunGetStringRange(run).location, nil)
                let yoffset = lineOrigins[i].y
                let drawRect = CGRect(x: xoffset, y: yoffset,  width, height: ascent+descent)
                if let imgName = runAttribute.object(forKey: "imageName") as? String {
                    let img = UIImage(named: imgName)
                    ctx.draw((img?.cgImage)!, in: drawRect)
                }
            }
        }
    }

 　　关键代码是

　　a.获取lineOrigin　　CTFrameGetLineOrigins(frame, CFRange(location: 0, length: 0), &lineOrigins)

　　b.获取width,height　　CTRunGetTypographicBounds(run, CFRange(location: 0, length: 0), &ascent, &descent, nil)　　//图片忽略leading属性

　　c.获取x偏移量　　lineOrigins[i].x+CTLineGetOffsetForStringIndex(line,CTRunGetStringRange(run).location,nil)

　　d.获取图片　　runAttributes.object(forKey:"imageName")