Display hidden characters in NSTextView

Question

I am writing a text editor for Mac OS X. I need to display hidden characters in an NSTextView (such as spaces, tabs, and special characters). I have spent a lot of time se

Answer 1

Here is Pol's solution in Swift:

class MyLayoutManager: NSLayoutManager {
    override func drawGlyphsForGlyphRange(glyphsToShow: NSRange, atPoint origin: NSPoint) {
        if let storage = self.textStorage {
            let s = storage.string
            let startIndex = s.startIndex
            for var glyphIndex = glyphsToShow.location; glyphIndex < glyphsToShow.location + glyphsToShow.length; glyphIndex++ {
                let characterIndex = self.characterIndexForGlyphAtIndex(glyphIndex)
                let ch = s[startIndex.advancedBy(characterIndex)]
                switch ch {
                case " ":
                    let attrs = storage.attributesAtIndex(characterIndex, effectiveRange: nil)
                    if let font = attrs[NSFontAttributeName] {
                        let g = font.glyphWithName("periodcentered")
                        self.replaceGlyphAtIndex(glyphIndex, withGlyph: g)
                    }
                case "\n":
                    let attrs = storage.attributesAtIndex(characterIndex, effectiveRange: nil)
                    if let font = attrs[NSFontAttributeName] {
//                        let g = font.glyphWithName("carriagereturn")
                        let g = font.glyphWithName("paragraph")
                        self.replaceGlyphAtIndex(glyphIndex, withGlyph: g)
                    }
                case "\t":
                    let attrs = storage.attributesAtIndex(characterIndex, effectiveRange: nil)
                    if let font = attrs[NSFontAttributeName] {
                        let g = font.glyphWithName("arrowdblright")
                        self.replaceGlyphAtIndex(glyphIndex, withGlyph: g)
                    }
                default:
                    break
                }
            }
        }
        super.drawGlyphsForGlyphRange(glyphsToShow, atPoint: origin)
    }
}

And to list the glyph names:

   func listFonts() {
        let font = CGFontCreateWithFontName("Menlo-Regular")
        for var i:UInt16 = 0; i < UInt16(CGFontGetNumberOfGlyphs(font)); i++ {
            if let name = CGFontCopyGlyphNameForGlyph(font, i) {
                print("name: \(name) at index \(i)")
            }
        }
    }