Light adaptation follow-ups: palette provenance, minimum-contrast, settings, iOS

apple/GhostteaApp/App/GhostteaAppModel.swift

@@ -965,6 +965,8 @@ extension GhostteaTerminalPresentationConfig {
       && palette == other.palette
       && backgroundOpacity == other.backgroundOpacity
       && backgroundOpacityCells == other.backgroundOpacityCells
+      && minimumContrast == other.minimumContrast
+      && lightAdaptation == other.lightAdaptation
       && fontSize == other.fontSize
       && fontFamilies == other.fontFamilies
       && paddingX == other.paddingX

apple/GhostteaApp/App/GhostteaSSHAppModel.swift

@@ -1408,6 +1408,8 @@ extension GhostteaTerminalPresentationConfig {
       palette: palette,
       backgroundOpacity: backgroundOpacity,
       backgroundOpacityCells: backgroundOpacityCells,
+      minimumContrast: minimumContrast,
+      lightAdaptation: lightAdaptation,
       fontSize: runtime.fontSize,
       fontFamilies: runtime.fontFamilies,
       paddingX: paddingX,

apple/GhostteaApp/App/GhostteaSettingsView.swift

@@ -135,6 +135,29 @@ private struct GhostteaAppearanceSettingsView: View {
         .foregroundStyle(.secondary)
       }
 
+      Section("Readability") {
+        Toggle(
+          "Restyle dark apps under light themes",
+          isOn: Binding(
+            get: { configuration.appearance.lightAdaptation == .auto },
+            set: { value in update { $0.lightAdaptation = value ? .auto : .off } }))
+        Picker(
+          "Minimum text contrast",
+          selection: Binding(
+            get: { configuration.appearance.minimumContrast },
+            set: { value in update { $0.minimumContrast = value } })
+        ) {
+          ForEach(contrastChoices, id: \.self) { ratio in
+            Text(contrastLabel(ratio)).tag(ratio)
+          }
+        }
+        Text(
+          "Apps that paint their own dark background are redrawn as a light design when a light theme is active. Text below the minimum contrast against its background is lightened or darkened, keeping its hue; 4.5:1 is the WCAG AA level for body text."
+        )
+        .font(.caption)
+        .foregroundStyle(.secondary)
+      }
+
       if !configuration.appearance.shaderEffects.isEmpty {
         Section("Shader order") {
           ForEach(configuration.appearance.shaderEffects, id: \.self) { id in
@@ -201,6 +224,17 @@ private struct GhostteaAppearanceSettingsView: View {
     configuration.applyAppearance(selection)
   }
 
+  /// The offered ratios, plus a hand-edited one so the picker can show it.
+  private var contrastChoices: [Double] {
+    let current = configuration.appearance.minimumContrast
+    let choices = GhostteaAppearanceSelection.minimumContrastChoices
+    return choices.contains(current) ? choices : (choices + [current]).sorted()
+  }
+
+  private func contrastLabel(_ ratio: Double) -> String {
+    ratio > 1 ? "\(ratio.formatted(.number.precision(.fractionLength(0...2)))):1" : "Off"
+  }
+
   private func shaderName(_ id: String) -> String {
     GhostteaShaderOption.available.first { $0.id == id }?.name ?? id
   }

apple/GhostteaKit/Sources/GhostteaAppearance/GhostteaAppearance.swift

@@ -88,19 +88,30 @@ public struct GhostteaAppearanceSelection: Equatable, Sendable {
   public var backgroundOpacityCells: Bool
   public var shaderEffects: [String]
   public var shaderAnimation: Bool
+  /// `ghosttea-light-adaptation`: restyle dark-painted apps under light themes.
+  public var lightAdaptation: GhostteaLightAdaptation
+  /// Ghostty `minimum-contrast` ratio (1 is off).
+  public var minimumContrast: Double
+
+  /// Ratios offered by Settings; 4.5:1 is the WCAG AA level for body text.
+  public static let minimumContrastChoices: [Double] = [1, 3, 4.5, 7]
 
   public init(
     theme: GhostteaColorTheme? = nil,
     backgroundOpacity: Double = 1,
     backgroundOpacityCells: Bool = false,
     shaderEffects: [String] = [],
-    shaderAnimation: Bool = false
+    shaderAnimation: Bool = false,
+    lightAdaptation: GhostteaLightAdaptation = .auto,
+    minimumContrast: Double = 1
   ) {
     self.theme = theme
     self.backgroundOpacity = backgroundOpacity
     self.backgroundOpacityCells = backgroundOpacityCells
     self.shaderEffects = shaderEffects
     self.shaderAnimation = shaderAnimation
+    self.lightAdaptation = lightAdaptation
+    self.minimumContrast = minimumContrast
   }
 
   public init(config: GhostteaConfigSnapshot) {
@@ -112,6 +123,8 @@ public struct GhostteaAppearanceSelection: Equatable, Sendable {
       ? [GhostteaShaderEffect.betterCRT.rawValue]
       : config.renderer.shaderEffects
     shaderAnimation = config.renderer.customShaderAnimation
+    lightAdaptation = config.renderer.lightAdaptation
+    minimumContrast = Double(config.renderer.minimumContrast)
   }
 }
 
@@ -237,6 +250,8 @@ public enum GhostteaConfigurationDraft {
   public static func appearanceBlock(_ selection: GhostteaAppearanceSelection) throws -> String {
     guard selection.backgroundOpacity.isFinite,
       (0...1).contains(selection.backgroundOpacity),
+      selection.minimumContrast.isFinite,
+      (1...21).contains(selection.minimumContrast),
       selection.shaderEffects.allSatisfy({ id in
         GhostteaShaderOption.available.contains { $0.id == id }
       })
@@ -268,6 +283,8 @@ public enum GhostteaConfigurationDraft {
     }
     lines += [
       "custom-shader-animation = \(selection.shaderAnimation)",
+      "ghosttea-light-adaptation = \(selection.lightAdaptation.rawValue)",
+      "minimum-contrast = \(contrastRatio(selection.minimumContrast))",
       appearanceBlockEnd,
     ]
     return lines.joined(separator: "\n")
@@ -434,6 +451,7 @@ public enum GhostteaConfigurationDraft {
     lines.append("custom-shader =")
     lines += config.renderer.shaderEffects.map { "custom-shader = \($0)" }
     lines.append("custom-shader-animation = \(config.renderer.customShaderAnimation)")
+    lines.append("minimum-contrast = \(contrastRatio(Double(config.renderer.minimumContrast)))")
     lines += config.renderer.palette.map { entry in
       "palette = \(entry.index)=\(GhostteaFriendlyConfigValues.hex(entry.color))"
     }
@@ -514,6 +532,15 @@ public enum GhostteaConfigurationDraft {
     String(format: "%.2f", locale: Locale(identifier: "en_US_POSIX"), value)
   }
 
+  /// Up to two decimals without trailing zeros, matching the desktop's
+  /// `minimum-contrast = 4.5` rather than `4.50`.
+  private static func contrastRatio(_ value: Double) -> String {
+    var text = String(format: "%.2f", locale: Locale(identifier: "en_US_POSIX"), value)
+    while text.hasSuffix("0") { text.removeLast() }
+    if text.hasSuffix(".") { text.removeLast() }
+    return text
+  }
+
   private static func isColor(_ value: String) -> Bool {
     value.range(of: "^#[0-9a-fA-F]{6}$", options: .regularExpression) != nil
   }

apple/GhostteaKit/Sources/GhostteaCore/GhostteaConfiguration.swift

@@ -24,6 +24,13 @@ public enum GhostteaRendererPostProcess: String, Codable, Sendable {
   case betterCRT = "better-crt"
 }
 
+/// Whether a light theme may restyle applications that paint their own dark
+/// backgrounds (`ghosttea-light-adaptation`).
+public enum GhostteaLightAdaptation: String, Codable, Sendable {
+  case auto
+  case off
+}
+
 public enum GhostteaShaderEffect: String, CaseIterable, Codable, Sendable {
   case betterCRT = "ghosttea:better-crt"
   case crt = "ghosttea:crt"
@@ -113,6 +120,9 @@ public struct GhostteaResolvedRendererConfig: Codable, Equatable, Sendable {
   public let palette: [GhostteaPaletteConfigEntry]
   public let backgroundOpacity: Float
   public let backgroundOpacityCells: Bool
+  /// WCAG contrast ratio text keeps against its cell background (1 = off).
+  public let minimumContrast: Float
+  public let lightAdaptation: GhostteaLightAdaptation
   public let fontSize: Float
   public let fontFamilies: [String]
   public let paddingX: [Float]
@@ -125,6 +135,7 @@ public struct GhostteaResolvedRendererConfig: Codable, Equatable, Sendable {
   private enum CodingKeys: String, CodingKey {
     case foreground, background, cursor, cursorText, selectionBackground, selectionForeground
     case palette, backgroundOpacity, backgroundOpacityCells
+    case minimumContrast, lightAdaptation
     case fontSize, fontFamilies, paddingX, paddingY, postProcess
     case shaderEffects, customShaderAnimation, customShaderPaths
   }
@@ -141,6 +152,9 @@ public struct GhostteaResolvedRendererConfig: Codable, Equatable, Sendable {
     backgroundOpacity = try values.decodeIfPresent(Float.self, forKey: .backgroundOpacity) ?? 1
     backgroundOpacityCells =
       try values.decodeIfPresent(Bool.self, forKey: .backgroundOpacityCells) ?? false
+    minimumContrast = try values.decodeIfPresent(Float.self, forKey: .minimumContrast) ?? 1
+    lightAdaptation =
+      try values.decodeIfPresent(GhostteaLightAdaptation.self, forKey: .lightAdaptation) ?? .auto
     fontSize = try values.decode(Float.self, forKey: .fontSize)
     fontFamilies = try values.decode([String].self, forKey: .fontFamilies)
     paddingX = try values.decode([Float].self, forKey: .paddingX)
@@ -169,6 +183,9 @@ public struct GhostteaTerminalPresentationConfig: Codable, Equatable, Sendable {
   public let palette: [GhostteaPaletteConfigEntry]
   public let backgroundOpacity: Float
   public let backgroundOpacityCells: Bool
+  /// WCAG contrast ratio text keeps against its cell background (1 = off).
+  public let minimumContrast: Float
+  public let lightAdaptation: GhostteaLightAdaptation
   public let fontSize: Float
   public let fontFamilies: [String]
   public let paddingX: [Float]
@@ -191,6 +208,8 @@ public struct GhostteaTerminalPresentationConfig: Codable, Equatable, Sendable {
     palette: [GhostteaPaletteConfigEntry] = [],
     backgroundOpacity: Float = 1,
     backgroundOpacityCells: Bool = false,
+    minimumContrast: Float = 1,
+    lightAdaptation: GhostteaLightAdaptation = .auto,
     fontSize: Float,
     fontFamilies: [String],
     paddingX: [Float],
@@ -211,6 +230,8 @@ public struct GhostteaTerminalPresentationConfig: Codable, Equatable, Sendable {
     self.palette = palette
     self.backgroundOpacity = backgroundOpacity
     self.backgroundOpacityCells = backgroundOpacityCells
+    self.minimumContrast = minimumContrast
+    self.lightAdaptation = lightAdaptation
     self.fontSize = fontSize
     self.fontFamilies = fontFamilies
     self.paddingX = paddingX
@@ -225,6 +246,7 @@ public struct GhostteaTerminalPresentationConfig: Codable, Equatable, Sendable {
     case schemaVersion, revision, foreground, background, cursor, cursorText
     case selectionBackground, selectionForeground, palette
     case backgroundOpacity, backgroundOpacityCells
+    case minimumContrast, lightAdaptation
     case fontSize, fontFamilies, paddingX, paddingY, postProcess
     case shaderEffects, customShaderAnimation, customShaderCount
   }
@@ -243,6 +265,9 @@ public struct GhostteaTerminalPresentationConfig: Codable, Equatable, Sendable {
     backgroundOpacity = try values.decodeIfPresent(Float.self, forKey: .backgroundOpacity) ?? 1
     backgroundOpacityCells =
       try values.decodeIfPresent(Bool.self, forKey: .backgroundOpacityCells) ?? false
+    minimumContrast = try values.decodeIfPresent(Float.self, forKey: .minimumContrast) ?? 1
+    lightAdaptation =
+      try values.decodeIfPresent(GhostteaLightAdaptation.self, forKey: .lightAdaptation) ?? .auto
     fontSize = try values.decode(Float.self, forKey: .fontSize)
     fontFamilies = try values.decode([String].self, forKey: .fontFamilies)
     paddingX = try values.decode([Float].self, forKey: .paddingX)
@@ -310,6 +335,8 @@ public struct GhostteaConfigSnapshot: Codable, Equatable, Sendable {
       palette: renderer.palette,
       backgroundOpacity: renderer.backgroundOpacity,
       backgroundOpacityCells: renderer.backgroundOpacityCells,
+      minimumContrast: renderer.minimumContrast,
+      lightAdaptation: renderer.lightAdaptation,
       fontSize: renderer.fontSize,
       fontFamilies: renderer.fontFamilies,
       paddingX: renderer.paddingX,

apple/GhostteaKit/Sources/GhostteaFrame/TRF1Decoder.swift

@@ -37,6 +37,7 @@ public struct TRF1SectionKind: RawRepresentable, Hashable, Sendable {
   public static let viewportMetadata = Self(rawValue: 9)
   public static let accessibilityText = Self(rawValue: 10)
   public static let clipboardWrite = Self(rawValue: 11)
+  public static let stylePalette = Self(rawValue: 13)
 }
 
 public struct TRF1Section: Sendable {
@@ -122,6 +123,45 @@ public struct TRF1StyleDefinition: Equatable, Sendable {
   public let underline: Bool
   public let foreground: TRF1RGB?
   public let background: TRF1RGB?
+  /// Palette index `foreground` was resolved from, when it came from the palette.
+  public let foregroundPalette: UInt8?
+  /// Palette index `background` was resolved from, when it came from the palette.
+  public let backgroundPalette: UInt8?
+
+  public init(
+    id: UInt32,
+    bold: Bool,
+    italic: Bool,
+    faint: Bool,
+    inverse: Bool,
+    invisible: Bool,
+    strikethrough: Bool,
+    underline: Bool,
+    foreground: TRF1RGB?,
+    background: TRF1RGB?,
+    foregroundPalette: UInt8? = nil,
+    backgroundPalette: UInt8? = nil
+  ) {
+    self.id = id
+    self.bold = bold
+    self.italic = italic
+    self.faint = faint
+    self.inverse = inverse
+    self.invisible = invisible
+    self.strikethrough = strikethrough
+    self.underline = underline
+    self.foreground = foreground
+    self.background = background
+    self.foregroundPalette = foregroundPalette
+    self.backgroundPalette = backgroundPalette
+  }
+}
+
+/// Palette provenance for one style definition (TRF1 section 13).
+public struct TRF1StylePaletteEntry: Equatable, Sendable {
+  public let styleID: UInt32
+  public let foreground: UInt8?
+  public let background: UInt8?
 }
 
 public enum TRF1CursorStyle: UInt8, Sendable {
@@ -421,7 +461,12 @@ public func decodeTRF1GlyphDefinitions(_ section: TRF1Section) throws -> [TRF1Gl
   return definitions
 }
 
-public func decodeTRF1StyleDefinitions(_ section: TRF1Section) throws -> [TRF1StyleDefinition] {
+/// Decodes style definitions. Pass the frame's optional style palette section
+/// to attach palette provenance; the RGB colors are complete without it.
+public func decodeTRF1StyleDefinitions(
+  _ section: TRF1Section,
+  palette paletteSection: TRF1Section? = nil
+) throws -> [TRF1StyleDefinition] {
   try requireKind(section, .styleDefinitions, "wrong style definition section kind")
   let reader = TRF1Reader(data: section.bytes)
   try reader.require(offset: 0, length: 4, "truncated style definition header")
@@ -469,7 +514,55 @@ public func decodeTRF1StyleDefinitions(_ section: TRF1Section) throws -> [TRF1St
       )
     )
   }
-  return styles
+  guard let paletteSection else { return styles }
+  var palette: [UInt32: TRF1StylePaletteEntry] = [:]
+  for entry in try decodeTRF1StylePalette(paletteSection) {
+    palette[entry.styleID] = entry
+  }
+  return styles.map { style in
+    guard let entry = palette[style.id] else { return style }
+    return TRF1StyleDefinition(
+      id: style.id,
+      bold: style.bold,
+      italic: style.italic,
+      faint: style.faint,
+      inverse: style.inverse,
+      invisible: style.invisible,
+      strikethrough: style.strikethrough,
+      underline: style.underline,
+      foreground: style.foreground,
+      background: style.background,
+      foregroundPalette: style.foreground == nil ? nil : entry.foreground,
+      backgroundPalette: style.background == nil ? nil : entry.background
+    )
+  }
+}
+
+public func decodeTRF1StylePalette(_ section: TRF1Section) throws -> [TRF1StylePaletteEntry] {
+  try requireKind(section, .stylePalette, "wrong style palette section kind")
+  let reader = TRF1Reader(data: section.bytes)
+  try reader.require(offset: 0, length: 4, "truncated style palette header")
+  let count = try reader.uint32(0, "truncated style palette header")
+  try require(count == section.itemCount, "style palette count mismatch")
+  try require(Int(count) <= (section.bytes.count - 4) / 8, "invalid style palette length")
+  try require(section.bytes.count == 4 + Int(count) * 8, "invalid style palette length")
+  var entries: [TRF1StylePaletteEntry] = []
+  entries.reserveCapacity(Int(count))
+  for index in 0..<Int(count) {
+    let offset = 4 + index * 8
+    let flags = try reader.uint8(offset + 4, "truncated style palette entry")
+    try require(flags & ~0x3 == 0, "invalid style palette flags")
+    let foreground = try reader.uint8(offset + 5, "truncated style palette entry")
+    let background = try reader.uint8(offset + 6, "truncated style palette entry")
+    entries.append(
+      TRF1StylePaletteEntry(
+        styleID: try reader.uint32(offset, "truncated style palette entry"),
+        foreground: flags & 1 != 0 ? foreground : nil,
+        background: flags & 2 != 0 ? background : nil
+      )
+    )
+  }
+  return entries
 }
 
 public func decodeTRF1CursorState(_ section: TRF1Section) throws -> TRF1CursorState {