How to get all characters of the font with CTFontCopyCharacterSet() in Swift? - swift

Question

How does one get all characters of the font with CTFontCopyCharacterSet() in Swift? ... for macOS?
The issue occured when implementing the approach from an OSX: CGGlyph to UniChar answer in Swift.
func createUnicodeFontMap() {
// Get all characters of the font with CTFontCopyCharacterSet().
let cfCharacterSet: CFCharacterSet = CTFontCopyCharacterSet(ctFont)
//
let cfCharacterSetStr = "\(cfCharacterSet)"
print("CFCharacterSet: \(cfCharacterSet)")
// Map all Unicode characters to corresponding glyphs
var unichars = [UniChar](…NYI…) // NYI: lacking unichars for CFCharacterSet
var glyphs = [CGGlyph](repeating: 0, count: unichars.count)
guard CTFontGetGlyphsForCharacters(
ctFont, // font: CTFont
&unichars, // characters: UnsafePointer<UniChar>
&glyphs, // UnsafeMutablePointer<CGGlyph>
unichars.count // count: CFIndex
)
else {
return
}
// For each Unicode character and its glyph,
// store the mapping glyph -> Unicode in a dictionary.
// ... NYI
}
What to do with CFCharacterSet to retrieve the actual characters has been elusive. Autocompletion of the cfCharacterSet instance offers show no relavant methods.
And the Core Foundation > CFCharacterSet appears have methods for creating another CFCharacterSet, but not something the provides an array|list|string of unichars to be able to create a mapped dictionary.
Note: I'm looking for a solution which is not specific to iOS as in Get all available characters from a font which uses UIFont.

Answer 1

CFCharacterSet is toll-free bridged with the Cocoa Foundation counterpart NSCharacterSet, and can be bridged to the corresponding Swift value type CharacterSet:
let charset = CTFontCopyCharacterSet(ctFont) as CharacterSet
Then the approach from NSArray from NSCharacterSet can be used to enumerate all Unicode scalar values of that character set (including non-BMP points, i.e. Unicode scalar values greater than U+FFFF).
The CTFontGetGlyphsForCharacters() expects non-BMP characters as surrogate pair, i.e. as an array of UTF-16 code units.
Putting it together, the function would look like this:
func createUnicodeFontMap(ctFont: CTFont) -> [CGGlyph : UnicodeScalar] {
let charset = CTFontCopyCharacterSet(ctFont) as CharacterSet
var glyphToUnicode = [CGGlyph : UnicodeScalar]() // Start with empty map.
// Enumerate all Unicode scalar values from the character set:
for plane: UInt8 in 0...16 where charset.hasMember(inPlane: plane) {
for unicode in UTF32Char(plane) << 16 ..< UTF32Char(plane + 1) << 16 {
if let uniChar = UnicodeScalar(unicode), charset.contains(uniChar) {
// Get glyph for this `uniChar` ...
let utf16 = Array(uniChar.utf16)
var glyphs = [CGGlyph](repeating: 0, count: utf16.count)
if CTFontGetGlyphsForCharacters(ctFont, utf16, &glyphs, utf16.count) {
// ... and add it to the map.
glyphToUnicode[glyphs[0]] = uniChar
}
}
}
}
return glyphToUnicode
}

Answer 2

You can do something like this.
let cs = CTFontCopyCharacterSet(font) as NSCharacterSet
let bitmapRepresentation = cs.bitmapRepresentation
The format of the bitmap is defined in the reference page for CFCharacterSetCreateWithBitmapRepresentation