swift - 无论我做什么，NSLayoutManager 都会隐藏换行符

我试图在我的 NSTextView 子类中显示不可见的字符，比如换行符。像覆盖 NSLayoutManager 的 drawGlyph 方法这样的常用方法是一个坏主意，因为它太慢并且不能在多页面布局中正常工作。

我想要做的是覆盖 NSLayoutManager 的 setGlyph 方法，以便它将不可见的“\n”字形替换为“¶”字形，将“”替换为“∙”。

它适用于“”空格字形，但对换行符没有影响。

public override func setGlyphs(_ glyphs: UnsafePointer<CGGlyph>, properties props: UnsafePointer<NSGlyphProperty>, characterIndexes charIndexes: UnsafePointer<Int>, font aFont: Font, forGlyphRange glyphRange: NSRange) {
    var substring = (self.currentTextStorage.string as NSString).substring(with: glyphRange)

    // replace invisible characters with visible
    if PreferencesManager.shared.shouldShowInvisibles == true {
        substring = substring.replacingOccurrences(of: " ", with: "\u{00B7}")
        substring = substring.replacingOccurrences(of: "\n", with: "u{00B6}")
    }

    // create a CFString
    let stringRef = substring as CFString
    let count = CFStringGetLength(stringRef)

    // convert processed string to the C-pointer
    let cfRange = CFRangeMake(0, count)
    let fontRef = CTFontCreateWithName(aFont.fontName as CFString?, aFont.pointSize, nil)
    let characters = UnsafeMutablePointer<UniChar>.allocate(capacity: MemoryLayout<UniChar>.size * count)
    CFStringGetCharacters(stringRef, cfRange, characters)

    // get glyphs for the pointer of characters
    let glyphsRef = UnsafeMutablePointer<CGGlyph>.allocate(capacity: MemoryLayout<CGGlyph>.size * count)
    CTFontGetGlyphsForCharacters(fontRef, characters, glyphsRef, count)

    // set those glyphs
    super.setGlyphs(glyphsRef, properties:props, characterIndexes: charIndexes, font: aFont, forGlyphRange: glyphRange)
}

然后我想出了一个想法:它看起来像 NSTypesetter 标记新的行字符范围，就像它根本不应该处理的那样。所以我继承了 NSTypesetter 并重写了一个方法:

override func setNotShownAttribute(_ flag: Bool, forGlyphRange glyphRange: NSRange) {
    let theFlag = PreferencesManager.shared.shouldShowInvisibles == true ? false : true
    super.setNotShownAttribute(theFlag, forGlyphRange: glyphRange)
}

但它不起作用。无论我创建什么字形，NSLayoutManager 仍然不会为新行字符生成字形。

我究竟做错了什么？

最佳答案

正如我发现的那样，类的 NSTypesetter 的 setNotShownAttribute: 的默认实现不会更改其字形存储中已生成的字形。所以，调用 super 不会产生任何效果。我只需要在调用 super 之前手动替换字形。

因此，显示不可见字符的最有效实现(缩放 View 时您会看到差异)是这样的:

这种方法的局限性: 如果你的应用程序必须在文本 View 中有多种字体，那么这种方法可能不是一个好主意，因为那些显示的不可见字符的字体也会不同。这不是您可能想要实现的目标。

子类 NSLayoutManager 并覆盖 setGlyphs 以显示空格字符:

public override func setGlyphs(_ glyphs: UnsafePointer<CGGlyph>, properties props: UnsafePointer<NSGlyphProperty>, characterIndexes charIndexes: UnsafePointer<Int>, font aFont: Font, forGlyphRange glyphRange: NSRange) {
    var substring = (self.currentTextStorage.string as NSString).substring(with: glyphRange)

    // replace invisible characters with visible
    if PreferencesManager.shared.shouldShowInvisibles == true {
        substring = substring.replacingOccurrences(of: " ", with: "\u{00B7}")
    }

    // create a CFString
    let stringRef = substring as CFString
    let count = CFStringGetLength(stringRef)

    // convert processed string to the C-pointer
    let cfRange = CFRangeMake(0, count)
    let fontRef = CTFontCreateWithName(aFont.fontName as CFString?, aFont.pointSize, nil)
    let characters = UnsafeMutablePointer<UniChar>.allocate(capacity: MemoryLayout<UniChar>.size * count)
    CFStringGetCharacters(stringRef, cfRange, characters)

    // get glyphs for the pointer of characters
    let glyphsRef = UnsafeMutablePointer<CGGlyph>.allocate(capacity: MemoryLayout<CGGlyph>.size * count)
    CTFontGetGlyphsForCharacters(fontRef, characters, glyphsRef, count)

    // set those glyphs
    super.setGlyphs(glyphsRef, properties:props, characterIndexes: charIndexes, font: aFont, forGlyphRange: glyphRange)
}

子类 NSATSTypesetter 并将其分配给您的 NSLayoutManager 子类。子类将显示换行符，并确保每个不可见的字符都用不同的颜色绘制:

class CustomTypesetter: NSATSTypesetter {

    override func setNotShownAttribute(_ flag: Bool, forGlyphRange glyphRange: NSRange) {
        var theFlag = flag

        if PreferencesManager.shared.shouldShowInvisibles == true   {
            theFlag = false

            // add new line glyphs into the glyph storage
            var newLineGlyph = yourFont.glyph(withName: "paragraph")
            self.substituteGlyphs(in: glyphRange, withGlyphs: &newLineGlyph)

            // draw new line char with different color
            self.layoutManager?.addTemporaryAttribute(NSForegroundColorAttributeName, value: NSColor.invisibleTextColor, forCharacterRange: glyphRange)
        }

        super.setNotShownAttribute(theFlag, forGlyphRange: glyphRange)
    }

    /// Currently hadn't found any faster way to draw space glyphs with different color
    override func setParagraphGlyphRange(_ paragraphRange: NSRange, separatorGlyphRange paragraphSeparatorRange: NSRange) {
        super.setParagraphGlyphRange(paragraphRange, separatorGlyphRange: paragraphSeparatorRange)

        guard PreferencesManager.shared.shouldShowInvisibles == true else { return }

        if let substring = (self.layoutManager?.textStorage?.string as NSString?)?.substring(with: paragraphRange) {
            let expression = try? NSRegularExpression.init(pattern: "\\s", options: NSRegularExpression.Options.useUnicodeWordBoundaries)
            let sunstringRange = NSRange(location: 0, length: substring.characters.count)

            if let matches = expression?.matches(in: substring, options: NSRegularExpression.MatchingOptions.withoutAnchoringBounds, range: sunstringRange) {
                for match in matches {
                    let globalSubRange = NSRange(location: paragraphRange.location + match.range.location, length: 1)
                    self.layoutManager?.addTemporaryAttribute(NSForegroundColorAttributeName, value: Color.invisibleText, forCharacterRange: globalSubRange)
                }
            }
        }
    }
}

要显示/隐藏不可见字符，只需调用:

let storageRange = NSRange(location: 0, length: currentTextStorage.length)
layoutManager.invalidateGlyphs(forCharacterRange: storageRange, changeInLength: 0, actualCharacterRange: nil)
layoutManager.ensureGlyphs(forGlyphRange: storageRange)

关于swift - 无论我做什么，NSLayoutManager 都会隐藏换行符，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/39545718/