Add DynamicTypeSize (#215)

Author: Kyle-Ye

Sources/OpenSwiftUICore/Text/DynamicTypeSize.swift

@@ -0,0 +1,124 @@
+//
+//  DynamicTypeSize.swift
+//  OpenSwiftUICore
+//
+//  Audited for iOS 18.0
+//  Status: Complete
+//  ID: B498FA81088CF7FADFFFFFC897E05C74 (SwiftUICore)
+
+/// A Dynamic Type size, which specifies how large scalable content should be.
+///
+/// For more information, see
+/// [Typography](https://developer.apple.com/design/human-interface-guidelines/ios/visual-design/typography/)
+/// in the Human Interface Guidelines.
+public enum DynamicTypeSize: Hashable, Comparable, CaseIterable, Sendable {
+    /// An extra small size.
+    case xSmall
+
+    /// A small size.
+    case small
+
+    /// A medium size.
+    case medium
+
+    /// A large size.
+    case large
+
+    /// An extra large size.
+    case xLarge
+
+    /// An extra extra large size.
+    case xxLarge
+
+    /// An extra extra extra large size.
+    case xxxLarge
+
+    /// The first accessibility size.
+    case accessibility1
+
+    /// The second accessibility size.
+    case accessibility2
+
+    /// The third accessibility size.
+    case accessibility3
+
+    /// The fourth accessibility size.
+    case accessibility4
+
+    /// The fifth accessibility size.
+    case accessibility5
+
+    /// A Boolean value indicating whether the size is one that is associated
+    /// with accessibility.
+    public var isAccessibilitySize: Bool {
+        switch self {
+        case .accessibility1, .accessibility2, .accessibility3, .accessibility4, .accessibility5: true
+        default: false
+        }
+    }
+
+    package static var systemDefault: DynamicTypeSize {
+        .large
+        // CoreGlue2.shared.systemDefaultDynamicTypeSize
+    }
+}
+
+private struct DynamicTypeSizeKey: EnvironmentKey {
+    static var defaultValue: DynamicTypeSize { .large }
+}
+
+extension EnvironmentValues {
+    public var dynamicTypeSize: DynamicTypeSize {
+        get { self[DynamicTypeSizeKey.self] }
+        set { self[DynamicTypeSizeKey.self] = newValue }
+    }
+}
+
+extension View {
+    nonisolated public func dynamicTypeSize(_ size: DynamicTypeSize) -> some View {
+        self.environment(\.dynamicTypeSize, size)
+    }
+
+    nonisolated public func dynamicTypeSize<T>(_ range: T) -> some View where T: RangeExpression, T.Bound == DynamicTypeSize {
+        self.transformEnvironment(\.dynamicTypeSize) { $0 = $0.clamped(to: range) }
+    }
+}
+
+private struct DynamicTypeSizeCollection: Collection {
+    func index(after i: DynamicTypeSize) -> DynamicTypeSize {
+        let index = DynamicTypeSize.allCases.firstIndex(of: i)!
+        let targetIndex = index + 1
+        let count = DynamicTypeSize.allCases.count
+        let resultIndex = targetIndex < count ? targetIndex : count-1
+        return DynamicTypeSize.allCases[resultIndex]
+    }
+    
+    subscript(position: DynamicTypeSize) -> Element {
+        _read { yield position }
+    }
+
+    typealias Index = DynamicTypeSize
+
+    typealias Element = DynamicTypeSize
+
+    var startIndex: Index { .small }
+
+    var endIndex: Index { .accessibility5 }
+}
+
+extension DynamicTypeSize {
+    package func clamped<T>(to range: T) -> DynamicTypeSize where T: RangeExpression, T.Bound == DynamicTypeSize {
+        let bound = range.relative(to: DynamicTypeSizeCollection())
+
+        let upperBound: DynamicTypeSize
+        if range.contains(bound.upperBound) {
+            upperBound = bound.upperBound
+        } else {
+            let index = DynamicTypeSize.allCases.firstIndex(of: bound.upperBound)!
+            let targetIndex = index + 1
+            let resultIndex = max(0, index)
+            upperBound = DynamicTypeSize.allCases[resultIndex]
+        }
+        return clamp(min: bound.lowerBound, max: upperBound)
+    }
+}