Implement Math view

Sources/SwiftUIMath/Font.swift

@@ -1,4 +1,4 @@
-import Foundation
+import SwiftUI
 
 extension Math {
   public struct Font: Hashable, Sendable {
@@ -33,3 +33,13 @@ extension Math.Font.Name {
   public static let garamond: Self = "Garamond-Math"
   public static let leteSans: Self = "LeteSansMath"
 }
+
+extension View {
+  public func mathFont(_ font: Math.Font) -> some View {
+    environment(\.mathFont, font)
+  }
+}
+
+extension EnvironmentValues {
+  @Entry var mathFont = Math.Font(name: .latinModern, size: 20)
+}

Sources/SwiftUIMath/Internal/Display/DisplayNode.swift

@@ -13,7 +13,7 @@ extension Math {
     var localTextColor: CGColor?
     var localBackgroundColor: CGColor?
 
-    func bounds() -> CGRect {
+    var bounds: CGRect {
       CGRect(x: position.x, y: position.y - descent, width: width, height: ascent + descent)
     }
   }

Sources/SwiftUIMath/Internal/Display/DisplayProvider.swift

@@ -0,0 +1,118 @@
+import Foundation
+
+extension Math {
+  final class DisplayProvider: Sendable {
+    private struct Cache {
+      struct Key: Hashable {
+        let latex: String
+        let font: Font
+        let style: TypesettingStyle
+        let proposedWidth: CGFloat
+      }
+
+      let atomList = NSCache<NSString, AtomList>()
+      let displayNode = NSCache<KeyBox<Key>, DisplayNode>()
+    }
+
+    static let shared = DisplayProvider()
+
+    private let cache = ReadWriteLockIsolated<Cache>(Cache())
+
+    func sizeThatFits(
+      proposedWidth width: CGFloat,
+      latex: String,
+      font: Font,
+      style: TypesettingStyle
+    ) -> CGSize {
+      display(
+        for: latex,
+        font: font,
+        style: style,
+        proposedWidth: width
+      )?.bounds.size ?? .zero
+    }
+
+    func display(
+      for latex: String,
+      font: Font,
+      style: TypesettingStyle,
+      proposedWidth: CGFloat
+    ) -> DisplayNode? {
+      cache.withValue { cache in
+        let roundedWidth = proposedWidth.halfPointRounded()
+        let key = KeyBox(
+          Cache.Key(
+            latex: latex,
+            font: font,
+            style: style,
+            proposedWidth: roundedWidth
+          )
+        )
+
+        if let displayNode = cache.displayNode.object(forKey: key) {
+          return displayNode
+        }
+
+        guard
+          let atomList = atomList(for: latex, cache: &cache),
+          let displayNode = Typesetter.createLineForMathList(
+            atomList,
+            font: .init(font: font),
+            style: .init(style),
+            maxWidth: roundedWidth
+          )
+        else {
+          return nil
+        }
+
+        cache.displayNode.setObject(displayNode, forKey: key)
+
+        if displayNode.width != roundedWidth {
+          // Cache the measured width to avoid a miss between layout and draw passes
+          let secondaryKey = KeyBox(
+            Cache.Key(
+              latex: latex,
+              font: font,
+              style: style,
+              proposedWidth: displayNode.width.halfPointRounded()
+            )
+          )
+          cache.displayNode.setObject(displayNode, forKey: secondaryKey)
+        }
+
+        return displayNode
+      }
+    }
+
+    private func atomList(for latex: String, cache: inout Cache) -> AtomList? {
+      if let atomList = cache.atomList.object(forKey: latex as NSString) {
+        return atomList
+      }
+
+      guard let atomList = Parser.build(fromString: latex) else {
+        return nil
+      }
+
+      cache.atomList.setObject(atomList, forKey: latex as NSString)
+      return atomList
+    }
+  }
+}
+
+extension Math.Style.Level {
+  fileprivate init(_ typesettingStyle: Math.TypesettingStyle) {
+    switch typesettingStyle {
+    case .display:
+      self = .display
+    case .text:
+      self = .text
+    }
+  }
+}
+
+extension CGFloat {
+  fileprivate func halfPointRounded() -> CGFloat {
+    guard self > 0 else { return 0 }
+    return (self * 2).rounded() / 2
+  }
+}

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

@@ -6,6 +6,7 @@ extension GraphicsContext {
 
     context.translateBy(x: 0, y: size.height)
     context.scaleBy(x: 1, y: -1)
+    context.translateBy(x: 0, y: displayNode.descent)
 
     let foregroundColor = foregroundColor.resolve(in: environment).cgColor
 

Sources/SwiftUIMath/Internal/Display/Typesetter.swift

@@ -1793,6 +1793,10 @@ extension Math {
       currentLine.addAttribute(
         kCTFontAttributeName as NSAttributedString.Key, value: styleFont.ctFont as Any,
         range: NSMakeRange(0, currentLine.length))
+      currentLine.addAttribute(
+        NSAttributedString.Key(kCTForegroundColorFromContextAttributeName as String),
+        value: true,
+        range: NSMakeRange(0, currentLine.length))
       /*assert(currentLineIndexRange.length == numCodePoints(currentLine.string),
        "The length of the current line: %@ does not match the length of the range (%d, %d)",
        currentLine, currentLineIndexRange.location, currentLineIndexRange.length);*/
@@ -2410,6 +2414,10 @@ extension Math {
         line.addAttribute(
           kCTFontAttributeName as NSAttributedString.Key, value: styleFont.ctFont,
           range: NSMakeRange(0, line.length))
+        line.addAttribute(
+          NSAttributedString.Key(kCTForegroundColorFromContextAttributeName as String),
+          value: true,
+          range: NSMakeRange(0, line.length))
         let attributedString = line.copy() as! NSAttributedString
         let ctLine = CTLineCreateWithAttributedString(attributedString)
         let displayAtom = DisplayTextRun(

Sources/SwiftUIMath/Internal/Font/FontRegistry.swift

@@ -4,14 +4,14 @@ import Foundation
 
 extension Math {
   final class FontRegistry: Sendable {
-    static let shared = FontRegistry()
-
     private struct Cache {
       var graphicsFonts: [Font.Name: CGFont] = [:]
       var tables: [Font.Name: FontTable] = [:]
       let fonts = NSCache<KeyBox<Font>, CTFont>()
     }
 
+    static let shared = FontRegistry()
+
     private let cache = ReadWriteLockIsolated<Cache>(Cache())
 
     func graphicsFont(named name: Font.Name) -> CGFont? {

Sources/SwiftUIMath/Math.swift

@@ -1,14 +1,185 @@
 import SwiftUI
 
 public struct Math: View {
-  public init() {
+  @Environment(\.mathFont) private var font
+  @Environment(\.mathTypesettingStyle) private var typesettingStyle
+  @Environment(\.mathRenderingMode) private var renderingMode
+
+  private let latex: String
+
+  public init(_ latex: String) {
+    self.latex = latex
   }
 
   public var body: some View {
-    Text("TODO: implement")
+    Layout(latex: latex, font: font, style: typesettingStyle) {
+      Canvas { context, size in
+        guard
+          let displayNode = DisplayProvider.shared.display(
+            for: latex,
+            font: font,
+            style: typesettingStyle,
+            proposedWidth: size.width
+          )
+        else {
+          return
+        }
+
+        switch renderingMode {
+        case .monochrome:
+          // Monochrome rendering with foreground style
+          context.draw(displayNode, size: size, with: .foreground)
+        case .multicolor(let base):
+          // Multicolor rendering with base color for uncolored elements
+          context.draw(displayNode, size: size, foregroundColor: base)
+        }
+      }
+    }
   }
 }
 
-#Preview {
+extension Math {
-  Math()
+  @_spi(Textual)
+  public struct TypographicBounds: Sendable {
+    @_spi(Textual)
+    public var origin: CGPoint
+
+    @_spi(Textual)
+    public var width: CGFloat
+
+    @_spi(Textual)
+    public var ascent: CGFloat
+
+    @_spi(Textual)
+    public var descent: CGFloat
+
+    @_spi(Textual)
+    public var size: CGSize {
+      .init(width: self.width, height: self.ascent + self.descent)
+    }
+
+    static let zero = TypographicBounds(origin: .zero, width: 0, ascent: 0, descent: 0)
+  }
+
+  @_spi(Textual)
+  public func typographicBounds(
+    fitting proposal: ProposedViewSize,
+    font: Font,
+    style: TypesettingStyle
+  ) -> TypographicBounds {
+    if let width = proposal.width, width <= 0 {
+      return .zero
+    }
+
+    return DisplayProvider.shared
+      .display(
+        for: self.latex,
+        font: font,
+        style: style,
+        proposedWidth: proposal.width ?? 0
+      )
+      .map {
+        TypographicBounds(
+          origin: $0.position,
+          width: $0.width,
+          ascent: $0.ascent,
+          descent: $0.descent
+        )
+      } ?? .zero
+  }
+}
+
+extension Math {
+  private struct Layout: SwiftUI.Layout {
+    let latex: String
+    let font: Font
+    let style: TypesettingStyle
+
+    func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
+      if let width = proposal.width, width <= 0 {
+        return .zero
+      }
+
+      return DisplayProvider.shared.sizeThatFits(
+        proposedWidth: proposal.width ?? 0,
+        latex: latex,
+        font: font,
+        style: style
+      )
+    }
+
+    func placeSubviews(
+      in bounds: CGRect,
+      proposal: ProposedViewSize,
+      subviews: Subviews,
+      cache: inout ()
+    ) {
+      if let view = subviews.first {
+        view.place(at: bounds.origin, proposal: .init(bounds.size))
+      }
+    }
+  }
+}
+
+#Preview("Display Style") {
+  Math("\\frac{1}{2}+\\sqrt{2}+\\sum_{i=1}^{n}x_i")
+    .mathFont(Math.Font(name: .latinModern, size: 24))
+    .foregroundStyle(
+      .linearGradient(
+        colors: [.red, .blue],
+        startPoint: .top,
+        endPoint: .bottom
+      )
+    )
+    .padding()
+}
+
+#Preview("Text Style") {
+  Math("\\int_0^1 x^2\\,dx = \\frac{1}{3}")
+    .mathTypesettingStyle(.text)
+    .mathFont(Math.Font(name: .libertinus, size: 20))
+    .padding()
+}
+
+#Preview("Large Operators") {
+  Math("\\lim_{n\\to\\infty}\\sum_{k=1}^{n}\\frac{1}{k^2}=\\frac{\\pi^2}{6}")
+    .mathTypesettingStyle(.display)
+    .mathFont(Math.Font(name: .xits, size: 22))
+    .padding()
+}
+
+#Preview("Matrix") {
+  Math("A=\\begin{pmatrix}1&2\\\\3&4\\end{pmatrix}")
+    .mathTypesettingStyle(.display)
+    .mathFont(Math.Font(name: .asana, size: 22))
+    .padding()
+}
+
+#Preview("Cases") {
+  Math("\\begin{cases} x + y = 5 \\\\ 2x - y = 1 \\end{cases}")
+    .mathTypesettingStyle(.display)
+    .mathFont(Math.Font(name: .termes, size: 22))
+    .padding()
+}
+
+#Preview("Accents And Scripts") {
+  Math("\\hat{x}+\\bar{y}+\\vec{z}+a_{i}^{2}")
+    .mathTypesettingStyle(.text)
+    .mathFont(Math.Font(name: .euler, size: 22))
+    .padding()
+}
+
+#Preview("Multicolor") {
+  Math("\\color{#cc0000}{a}+\\color{#00aa00}{b}+\\color{#0000cc}{c}")
+    .mathTypesettingStyle(.text)
+    .mathRenderingMode(.multicolor)
+    .mathFont(Math.Font(name: .latinModern, size: 22))
+    .padding()
+}
+
+#Preview("Multicolor 2") {
+  Math("\\textcolor{#ff8800}{\\int_0^1 x^2\\,dx}=\\textcolor{#0088ff}{\\frac{1}{3}}")
+    .mathRenderingMode(.multicolor)
+    .mathFont(Math.Font(name: .libertinus, size: 20))
+    .padding()
 }

Sources/SwiftUIMath/RenderingMode.swift

@@ -0,0 +1,22 @@
+import SwiftUI
+
+extension Math {
+  public enum RenderingMode: Sendable {
+    case monochrome
+    case multicolor(base: SwiftUI.Color)
+
+    static var multicolor: Self {
+      .multicolor(base: .primary)
+    }
+  }
+}
+
+extension View {
+  public func mathRenderingMode(_ mathRenderingMode: Math.RenderingMode) -> some View {
+    environment(\.mathRenderingMode, mathRenderingMode)
+  }
+}
+
+extension EnvironmentValues {
+  @Entry var mathRenderingMode: Math.RenderingMode = .monochrome
+}

Sources/SwiftUIMath/TypesettingStyle.swift

@@ -0,0 +1,18 @@
+import SwiftUI
+
+extension Math {
+  public enum TypesettingStyle: Sendable {
+    case display
+    case text
+  }
+}
+
+extension View {
+  public func mathTypesettingStyle(_ typesettingStyle: Math.TypesettingStyle) -> some View {
+    environment(\.mathTypesettingStyle, typesettingStyle)
+  }
+}
+
+extension EnvironmentValues {
+  @Entry var mathTypesettingStyle: Math.TypesettingStyle = .display
+}