Question

默认的布局管理器填充没有文本（最后一行除外）的背景颜色（通过NSAttributedString .backgroundColor属性指定）。

我通过对NSLayoutManager进行子类化并按如下方式覆盖func drawBackground(forGlyphRange glyphsToShow: NSRange, at origin: CGPoint)来实现了想要的效果：

override func drawBackground(forGlyphRange glyphsToShow: NSRange, at origin: CGPoint) {
    guard let textContainer = textContainers.first, let textStorage = textStorage else { fatalError() }

    // This just takes the color of the first character assuming the entire container has the same background color.
    // To support ranges of different colours, you'll need to draw each glyph separately, querying the attributed string for the
    // background color attribute for the range of each character.
    guard textStorage.length > 0, let backgroundColor = textStorage.attribute(.backgroundColor, at: 0, effectiveRange: nil) as? UIColor else { return }

    var lineRects = [CGRect]()

    // create an array of line rects to be drawn.
    enumerateLineFragments(forGlyphRange: glyphsToShow) { (_, usedRect, _, range, _) in
        var usedRect = usedRect
        let locationOfLastGlyphInLine = NSMaxRange(range)-1
        // Remove the space at the end of each line (except last).
        if self.isThereAWhitespace(at: locationOfLastGlyphInLine) {
            let lastGlyphInLineWidth = self.boundingRect(forGlyphRange: NSRange(location: locationOfLastGlyphInLine, length: 1), in: textContainer).width
            usedRect.size.width -= lastGlyphInLineWidth
        }
        lineRects.append(usedRect)
    }

    lineRects = adjustRectsToContainerHeight(rects: lineRects, containerHeight: textContainer.size.height)

    for (lineNumber, lineRect) in lineRects.enumerated() {
        guard let context = UIGraphicsGetCurrentContext() else { return }
        context.saveGState()
        context.setFillColor(backgroundColor.cgColor)
        context.fill(lineRect)
        context.restoreGState()
    }
}

private func isThereAWhitespace(at location: Int) -> Bool {
    return propertyForGlyph(at: location) == NSLayoutManager.GlyphProperty.elastic
}

但是，这不能解决在属性字符串中具有由range指定的多种颜色的可能性。我该如何实现？我看着fillBackgroundRectArray收效甚微。

Answer 1

或者，您可以根本不使用属性，就像这样：

所以首先我定义了这个结构：

struct HighlightBackground {
    let range: NSRange
    let color: NSColor
}

然后在我的NSTextView子类中：

var highlightBackgrounds = [HighlightBackground]()

override func setSelectedRanges(_ ranges: [NSValue], affinity: NSSelectionAffinity, stillSelecting stillSelectingFlag: Bool) {
    if stillSelectingFlag == false {
        return
    }

 // remove old ranges first
    highlightBackgrounds = highlightBackgrounds.filter { $0.color != .green }

    for value in ranges {
        let range = value.rangeValue

        highlightBackgrounds.append(HighlightBackground(range: range, color: .green))
    }

    super.setSelectedRanges(ranges, affinity: affinity, stillSelecting: stillSelectingFlag)
}

然后从您的draw(_ rect: NSRect)方法中调用它：

func showBackgrounds() {
    guard
        let context = NSGraphicsContext.current?.cgContext,
        let lm = self.layoutManager
    else { return }

    context.saveGState()
    //        context.translateBy(x: origin.x, y: origin.y)

    for bg in highlightBackgrounds {
        bg.color.setFill()

        let glRange = lm.glyphRange(forCharacterRange: bg.range, actualCharacterRange: nil)    
        for rect in lm.rectsForGlyphRange(glRange) {    
            let path = NSBezierPath(roundedRect: rect, xRadius: selectedTextCornerRadius, yRadius: selectedTextCornerRadius)
            path.fill()
        }
    }

    context.restoreGState()
}

最后，您可能需要在NSLayoutManager子类中使用它，尽管您也可以将其放在NSTextView子类中：

func rectsForGlyphRange(_ glyphsToShow: NSRange) -> [NSRect] {

    var rects = [NSRect]()
    guard
        let tc = textContainer(forGlyphAt: glyphsToShow.location, effectiveRange: nil)
    else { return rects }

    enumerateLineFragments(forGlyphRange: glyphsToShow) { _, _, _, effectiveRange, _ in
        let rect = self.boundingRect(forGlyphRange: NSIntersectionRange(glyphsToShow, effectiveRange), in: tc)
        rects.append(rect)
    }

    return rects
}

希望这对您也适用。

Answer 2

我该如何实现？

在这里，我达到您的目标的方式是，在著名的Lorem ipsum...内以不同的颜色突出显示“ sit” 术语，该术语足够多行测试。

this answer中提供了支持以下代码（Swift 5.1，iOS 13）的所有基础知识，出于清晰原因不会在此处复制⟹它们导致了结果<此后strong> 1 。

在您的情况下，您想突出显示字符串的某些特定部分，这意味着由于这些元素的内容，这些元素应具有专用的键属性⟹在我看来，textStorage才可以解决。

MyTextStorage.swift

// Sent when a modification appears via the 'replaceCharacters' method.
    override func processEditing() {

        var regEx: NSRegularExpression

        do {
            regEx = try NSRegularExpression.init(pattern: " sit ", options: .caseInsensitive)
            let stringLength = backingStorage.string.distance(from: backingStorage.string.startIndex,
                                                              to: backingStorage.string.endIndex)
            regEx.enumerateMatches(in: backingStorage.string,
                                   options: .reportCompletion,
                                   range: NSRange(location: 1, length: stringLength-1)) { (result, flags, stop) in

                                guard let result = result else { return }
                                self.setAttributes([NSAttributedString.Key.foregroundColor : UIColor.black, //To be seen above every colors.
                                                    NSAttributedString.Key.backgroundColor : UIColor.random()],
                                                   range: result.range)
            }
        } catch let error as NSError {
            print(error.description)
        }

        super.processEditing()
    }
}

//A random color is provided for each " sit " element to highlight the possible different colors in a string.
extension UIColor {
    static func random () -> UIColor {
        return UIColor(red: CGFloat.random(in: 0...1),
                       green: CGFloat.random(in: 0...1),
                       blue: CGFloat.random(in: 0...1),
                       alpha: 1.0)
    }
}

如果从此处构建并运行，则会得到结果 2 ，该结果表明在文本found中出现的每个“坐” 彩色背景都存在问题，⟹会有偏移量lineFragment和彩色背景矩形之间。 ?

我去看看您提到的fillBackgroundRectArray方法，以及哪个苹果公司声明它“用颜色填充背景矩形” ，而'是{ {1}}'：这里似乎很适合纠正布局问题。 ?

MyLayoutManager.swift

drawBackground

需要深入研究参数调整以具有通用公式，但对于本示例而言，它可以正常工作。

最后，我们得到的结果 3 使得一旦调整了正则表达式的条件，就可以使属性字符串中的范围指定多种颜色。 ???

NSLayoutManager：如何在只有可渲染字形的地方填充背景色

2 个答案: