Implement DisplayNode drawing

Package.swift

@@ -5,10 +5,10 @@ import PackageDescription
 let package = Package(
   name: "swiftui-math",
   platforms: [
-    .macOS(.v12),
-    .iOS(.v15),
-    .tvOS(.v15),
-    .watchOS(.v8),
+    .macOS(.v14),
+    .iOS(.v17),
+    .tvOS(.v17),
+    .watchOS(.v10),
     .visionOS(.v1),
   ],
   products: [

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

@@ -0,0 +1,227 @@
+import CoreGraphics
+import CoreText
+import Foundation
+
+extension CGContext {
+  func draw(_ displayNode: Math.DisplayNode, foregroundColor: CGColor) {
+    let foregroundColor =
+      displayNode.localTextColor?.cgColor
+      ?? displayNode.textColor?.cgColor
+      ?? foregroundColor
+
+    switch displayNode {
+    case let list as Math.DisplayList:
+      draw(list, foregroundColor: foregroundColor)
+    case let textRun as Math.DisplayTextRun:
+      draw(textRun, foregroundColor: foregroundColor)
+    case let glyph as Math.DisplayGlyph:
+      draw(glyph, foregroundColor: foregroundColor)
+    case let glyphRun as Math.DisplayGlyphRun:
+      draw(glyphRun, foregroundColor: foregroundColor)
+    case let fraction as Math.DisplayFraction:
+      draw(fraction, foregroundColor: foregroundColor)
+    case let radical as Math.DisplayRadical:
+      draw(radical, foregroundColor: foregroundColor)
+    case let line as Math.DisplayLine:
+      draw(line, foregroundColor: foregroundColor)
+    case let largeOperator as Math.DisplayLargeOperator:
+      draw(largeOperator, foregroundColor: foregroundColor)
+    case let accent as Math.DisplayAccent:
+      draw(accent, foregroundColor: foregroundColor)
+    default:
+      break
+    }
+  }
+}
+
+extension CGContext {
+  private func draw(_ list: Math.DisplayList, foregroundColor: CGColor) {
+    saveGState()
+
+    translateBy(x: list.position.x, y: list.position.y)
+    textPosition = .zero
+
+    for child in list.children {
+      draw(child, foregroundColor: foregroundColor)
+    }
+
+    restoreGState()
+  }
+
+  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)
+
+    saveGState()
+    textPosition = textRun.position
+    CTLineDraw(line, self)
+    restoreGState()
+  }
+
+  private func draw(_ glyph: Math.DisplayGlyph, foregroundColor: CGColor) {
+    guard let platformFont = Math.PlatformFont(font: glyph.font) else {
+      return
+    }
+
+    saveGState()
+
+    translateBy(x: glyph.position.x, y: glyph.position.y - glyph.shiftDown)
+    textPosition = .zero
+
+    setFillColor(foregroundColor)
+
+    var cgGlyph = CGGlyph(glyph.glyph)
+    var pos = CGPoint.zero
+    CTFontDrawGlyphs(platformFont.ctFont, &cgGlyph, &pos, 1, self)
+
+    restoreGState()
+  }
+
+  private func draw(_ glyphRun: Math.DisplayGlyphRun, foregroundColor: CGColor) {
+    guard let platformFont = Math.PlatformFont(font: glyphRun.font) else {
+      return
+    }
+
+    saveGState()
+
+    translateBy(x: glyphRun.position.x, y: glyphRun.position.y - glyphRun.shiftDown)
+    textPosition = .zero
+
+    setFillColor(foregroundColor)
+
+    var glyphs = glyphRun.glyphs.map { CGGlyph($0) }
+    var positions = glyphRun.offsets.map { CGPoint(x: 0, y: $0) }
+    CTFontDrawGlyphs(platformFont.ctFont, &glyphs, &positions, glyphs.count, self)
+
+    restoreGState()
+  }
+
+  private func draw(_ fraction: Math.DisplayFraction, foregroundColor: CGColor) {
+    if let numerator = fraction.numerator {
+      draw(numerator, foregroundColor: foregroundColor)
+    }
+    if let denominator = fraction.denominator {
+      draw(denominator, foregroundColor: foregroundColor)
+    }
+
+    guard fraction.lineThickness > 0 else {
+      return
+    }
+
+    saveGState()
+
+    setStrokeColor(foregroundColor)
+    setLineWidth(fraction.lineThickness)
+
+    let lineStart = CGPoint(
+      x: fraction.position.x,
+      y: fraction.position.y + fraction.linePosition
+    )
+    let lineEnd = CGPoint(
+      x: fraction.position.x + fraction.width,
+      y: lineStart.y
+    )
+
+    move(to: lineStart)
+    addLine(to: lineEnd)
+    strokePath()
+
+    restoreGState()
+  }
+
+  private func draw(_ radical: Math.DisplayRadical, foregroundColor: CGColor) {
+    if let radicand = radical.radicand {
+      draw(radicand, foregroundColor: foregroundColor)
+    }
+    if let degree = radical.degree {
+      draw(degree, foregroundColor: foregroundColor)
+    }
+
+    saveGState()
+
+    setStrokeColor(foregroundColor)
+    setFillColor(foregroundColor)
+
+    translateBy(x: radical.position.x + radical.radicalShift, y: radical.position.y)
+    textPosition = .zero
+
+    if let radicalGlyph = radical.radicalGlyph {
+      draw(radicalGlyph, foregroundColor: foregroundColor)
+    }
+
+    let heightFromTop = radical.topKern
+    let glyphWidth = radical.radicalGlyph?.width ?? 0
+    let radicandWidth = radical.radicand?.width ?? 0
+    let lineStart = CGPoint(
+      x: glyphWidth,
+      y: radical.ascent - heightFromTop - radical.lineThickness / 2
+    )
+    let lineEnd = CGPoint(x: lineStart.x + radicandWidth, y: lineStart.y)
+
+    setLineWidth(radical.lineThickness)
+    setLineCap(.round)
+    move(to: lineStart)
+    addLine(to: lineEnd)
+    strokePath()
+
+    restoreGState()
+  }
+
+  private func draw(_ line: Math.DisplayLine, foregroundColor: CGColor) {
+    if let inner = line.inner {
+      draw(inner, foregroundColor: foregroundColor)
+    }
+
+    saveGState()
+
+    setStrokeColor(foregroundColor)
+    setLineWidth(line.lineThickness)
+
+    let lineStart = CGPoint(x: line.position.x, y: line.position.y + line.lineShiftUp)
+    let lineEnd = CGPoint(x: lineStart.x + (line.inner?.width ?? 0), y: lineStart.y)
+
+    move(to: lineStart)
+    addLine(to: lineEnd)
+    strokePath()
+
+    restoreGState()
+  }
+
+  private func draw(_ largeOperator: Math.DisplayLargeOperator, foregroundColor: CGColor) {
+    if let upperLimit = largeOperator.upperLimit {
+      draw(upperLimit, foregroundColor: foregroundColor)
+    }
+    if let lowerLimit = largeOperator.lowerLimit {
+      draw(lowerLimit, foregroundColor: foregroundColor)
+    }
+    if let nucleus = largeOperator.nucleus {
+      draw(nucleus, foregroundColor: foregroundColor)
+    }
+  }
+
+  private func draw(_ accent: Math.DisplayAccent, foregroundColor: CGColor) {
+    if let accentee = accent.accentee {
+      draw(accentee, foregroundColor: foregroundColor)
+    }
+
+    guard let accentGlyph = accent.accent else {
+      return
+    }
+
+    saveGState()
+
+    translateBy(x: accent.position.x, y: accent.position.y)
+    textPosition = .zero
+    draw(accentGlyph, foregroundColor: foregroundColor)
+
+    restoreGState()
+  }
+}

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

@@ -0,0 +1,27 @@
+import SwiftUI
+
+extension GraphicsContext {
+  func draw(_ displayNode: Math.DisplayNode, size: CGSize, foregroundColor: Color) {
+    var context = self
+
+    context.translateBy(x: 0, y: size.height)
+    context.scaleBy(x: 1, y: -1)
+
+    let foregroundColor = foregroundColor.resolve(in: environment).cgColor
+
+    context.withCGContext { cgContext in
+      cgContext.draw(displayNode, foregroundColor: foregroundColor)
+    }
+  }
+
+  func draw(_ displayNode: Math.DisplayNode, size: CGSize, with shading: GraphicsContext.Shading) {
+    var context = self
+
+    context.fill(Path(CGRect(origin: .zero, size: size)), with: shading)
+    context.blendMode = .destinationIn
+
+    context.drawLayer {
+      $0.draw(displayNode, size: size, foregroundColor: .black)
+    }
+  }
+}