无论我做什么，NSLayoutManager都会隐藏新行字符

Question

我试图在我的NSTextView子类中显示不可见的字符，如新行字符。像覆盖NSLayoutManager的drawGlyph方法这样的常用方法是一个坏主意，因为它太慢而且在多页面布局中无法正常工作。

我要做的是覆盖NSLayoutManager的setGlyph方法，以便用“¶”字形替换不可见的“\ n”字形，用“∙”替换“”。

它适用于“”空格字形，但对新行字符没有影响。

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)
}

然后我提出了一个想法：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。所以我将NSTypesetter子类化并覆盖了一个方法：

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？

Answer 1

正如我所知，该类的NSTypesetter的setNotShownAttribute：的默认实现不会改变其字形存储中已生成的字形。所以，超级电话不会产生任何影响。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（您将在缩放视图时看到差异）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视图中有多个字体，那么这种方法可能不是一个好主意，因为那些显示不可见字符的字体也会有所不同。这不是你想要达到的目标。

1. 子类NSLayoutManager并覆盖setGlyphs以显示空间字符：

   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)
   }

2. 子类NSATSTypesetter并将其分配给NSLayoutManager子类。子类将显示新的行字符，并确保使用不同的颜色绘制每个不可见的字符：

   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)
                   }
               }
           }
       }
   }

3. 要显示/隐藏不可见的字符，只需调用：

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

Answer 2

这可能超过了这个问题的实用性，但我是通过Google来到这里的。

至少在macOS 10.14上进行测试时，-[NSLayoutManager setNotShownAttribute:forGlyphAtIndex:]能够在生成该索引的字形后更改其值。关键是，在布线的最后，它将无条件地为换行符号设置setNotShownAttribute:YES。你完成后会得到-[NSLayoutManagerDelegate layoutManager:shouldUseAction:forControlCharacterAtIndex:]，你可以在那里重置它：

- (NSControlCharacterAction)layoutManager:(NSLayoutManager *)layoutManager shouldUseAction:(NSControlCharacterAction)action forControlCharacterAtIndex:(NSUInteger)characterIndex {
  if (layoutManager.showsInvisibleCharacters && (action & NSControlCharacterActionLineBreak)) {
    [layoutManager setNotShownAttribute:NO forGlyphAtIndex:[layoutManager glyphIndexForCharacterAtIndex:characterIndex]];
  }

  return action;
}

func layoutManager(_ layoutManager: NSLayoutManager, shouldUse action: NSLayoutManager.ControlCharacterAction, forControlCharacterAt characterIndex: Int) -> NSLayoutManager.ControlCharacterAction {
  if layoutManager.showsInvisibleCharacters, action.contains(.lineBreak) {
    let glyphIndex = layoutManager.glyphIndexForCharacter(at: characterIndex)
    layoutManager.setNotShownAttribute(false, forGlyphAt: glyphIndex)
  }

  return action
}

您会注意到我在示例中使用showsInvisibleCharacters，它实际上适用于内置方法，即使它没有该字符的映射，产生“我不知道”的字形：

使用-[NSLayoutManagerDelegate layoutManager:shouldGenerateGlyphs:properties:characterIndexes:font:forGlyphRange:，您可以使其完美运行：