Core Text calculate letter AND ruby annotation frames in iOS with Swift

How can I get the bounding box for each ruby annotation character (or furigana) in a CTFrame text rendered by CoreText and CoreGraphics in iOS? (iOS 11, 12 or 13)


I made a swift version program that encloses each character in a red box but I wasn't able to get the bounding boxes for the ruby annotation characters, *aka furigana*. I painted in green the ruby character boxes for the purpose of this question. (Please see the image in the GitHub link)

How can I achieve that? Any Ideas?

Edit: For clarity, the green boxes were painted by hand in an illustration software. I need to draw the green boxes by code.

The full source is in GitHub https://github.com/huse360/LetterFrame
This is the main source code:

Code Block 
	 override func draw(_ rect: CGRect) {
					guard let context = UIGraphicsGetCurrentContext() else { return }
			 
				
				 context.textMatrix = .identity
				 context.translateBy(x: 0, y: self.bounds.size.height)
				 context.scaleBy(x: 1.0, y: -1.0)
			 
				
				 let string = "｜優勝《ゆうしょう》の｜懸《か》かった｜試合《しあい》。｜Test《テスト》.\nThe quick brown fox jumps over the lazy dog. 12354567890 @#-+"
	
				
				 let attributedString = Utility.sharedInstance.furigana(String: string)
			 
				 let range = attributedString.mutableString.range(of: attributedString.string)
				 attributedString.addAttribute(.font, value: font, range: range)
			 
				 let framesetter = attributedString.framesetter()
			 
				 let textBounds = self.bounds.insetBy(dx: 20, dy: 20)
				 let frame = framesetter.createFrame(textBounds)
				
	//Draw the frame text:
			 
				 frame.draw(in: context)
							 
				 let origins = frame.lineOrigins()
			 
				 let lines = frame.lines()
					context.setStrokeColor(UIColor.red.cgColor)
					context.setLineWidth(0.7)
					for i in 0 ..< origins.count {
							let line = lines[i]
						 
							for run in line.glyphRuns() {
								
									let font = run.font
									let glyphPositions = run.glyphPositions()
									let glyphs = run.glyphs()
								
									let glyphsBoundingRects =	font.boundingRects(of: glyphs)
								
	//DRAW the bounding box for each glyph:
								
									for k in 0 ..< glyphPositions.count {
											let point = glyphPositions[k]
											let gRect = glyphsBoundingRects [k]
								
											var box = gRect
											box.origin +=	point + origins[i] + textBounds.origin
											context.stroke(box)
														
									}// for k
						
							}//for run
						
				 }//for i
				
			}//func draw