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

Question

我试图在我的 NSTextView 子类中显示不可见字符，例如换行符。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正确处理多页布局。

我想做的是重写 NSLayoutManager 的 setGlyph 方法，这样它将用“¶”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)
}

然后我想出了一个主意:看起来 NSTypesetter 标记了新的行字符范围，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 仍然不会为换行符生成字形。

我做错了什么？

Answer 1

正如我发现的那样，NSTypesetter 的 setNotShownAttribute: 类的默认实现不会更改其字形存储中已经生成的字形。因此，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:如果您的应用必须在 TextView 中使用多种字体，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会有所不同出色地。这不是您想要实现的目标。

1. 继承 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)
   }
   

2. 子类 NSATSTypesetter 并将其分配给您的 NSLayoutManager 子类。子类将显示新行字符并确保每个不可见字符都将以不同的颜色绘制:

   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)
                   }
               }
           }
       }
   }
   

3. 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)