Fix text run display node

Sources/SwiftUIMath/Internal/Display/CGContext+DisplayNode.swift

@@ -49,18 +49,10 @@ extension CGContext {
   }
 
   private func draw(_ textRun: Math.DisplayTextRun, foregroundColor: CGColor) {
-    guard let platformFont = Math.PlatformFont(font: textRun.font) else {
-      return
-    }
-
-    let attributes: [NSAttributedString.Key: Any] = [
-      NSAttributedString.Key(kCTFontAttributeName as String): platformFont.ctFont,
-      NSAttributedString.Key(kCTForegroundColorAttributeName as String): foregroundColor,
-    ]
-    let attributedString = NSAttributedString(string: textRun.text, attributes: attributes)
-    let line = CTLineCreateWithAttributedString(attributedString)
+    let line = CTLineCreateWithAttributedString(textRun.attributedString)
 
     saveGState()
+    setFillColor(foregroundColor)
     textPosition = textRun.position
     CTLineDraw(line, self)
     restoreGState()

Sources/SwiftUIMath/Internal/Display/DisplayTextRun.swift

@@ -3,14 +3,19 @@ import Foundation
 
 extension Math {
   final class DisplayTextRun: DisplayNode {
-    var text: String
+    var attributedString: NSAttributedString
     var font: Math.Font
     var atoms: [Math.Atom]
+    var text: String { attributedString.string }
 
     init(
-      text: String, font: Math.Font, position: CGPoint = .zero, range: NSRange, atoms: [Math.Atom]
+      attributedString: NSAttributedString,
+      font: Math.Font,
+      position: CGPoint = .zero,
+      range: NSRange,
+      atoms: [Math.Atom]
     ) {
-      self.text = text
+      self.attributedString = attributedString
       self.font = font
       self.atoms = atoms
       super.init()

Sources/SwiftUIMath/Internal/Display/Typesetter.swift

@@ -1794,9 +1794,10 @@ extension Math {
        "The length of the current line: %@ does not match the length of the range (%d, %d)",
        currentLine, currentLineIndexRange.location, currentLineIndexRange.length);*/
 
-      let line = CTLineCreateWithAttributedString(currentLine)
+      let attributedString = currentLine.copy() as! NSAttributedString
+      let line = CTLineCreateWithAttributedString(attributedString)
       let displayAtom = DisplayTextRun(
-        text: currentLine.string,
+        attributedString: attributedString,
         font: styleFont.font,
         position: currentPosition,
         range: currentLineIndexRange,
@@ -2406,9 +2407,10 @@ extension Math {
         line.addAttribute(
           kCTFontAttributeName as NSAttributedString.Key, value: styleFont.ctFont,
           range: NSMakeRange(0, line.length))
-        let ctLine = CTLineCreateWithAttributedString(line)
+        let attributedString = line.copy() as! NSAttributedString
+        let ctLine = CTLineCreateWithAttributedString(attributedString)
         let displayAtom = DisplayTextRun(
-          text: line.string,
+          attributedString: attributedString,
           font: styleFont.font,
           position: currentPosition,
           range: op.indexRange,