Add LinearGradient and UnitPoint

Author: colemancda

AndroidSwiftUICore/Sources/AndroidSwiftUICore/Primitives/Gradient.swift

@@ -0,0 +1,57 @@
+//
+//  Gradient.swift
+//  AndroidSwiftUICore
+//
+
+/// A location in a view, normalized to its size (0…1 on each axis).
+public struct UnitPoint: Equatable, Sendable {
+    public var x: Double
+    public var y: Double
+    public init(x: Double, y: Double) { self.x = x; self.y = y }
+
+    public static let leading = UnitPoint(x: 0, y: 0.5)
+    public static let trailing = UnitPoint(x: 1, y: 0.5)
+    public static let top = UnitPoint(x: 0.5, y: 0)
+    public static let bottom = UnitPoint(x: 0.5, y: 1)
+    public static let topLeading = UnitPoint(x: 0, y: 0)
+    public static let topTrailing = UnitPoint(x: 1, y: 0)
+    public static let bottomLeading = UnitPoint(x: 0, y: 1)
+    public static let bottomTrailing = UnitPoint(x: 1, y: 1)
+    public static let center = UnitPoint(x: 0.5, y: 0.5)
+}
+
+/// An ordered list of colors for a gradient.
+public struct Gradient: Equatable, Sendable {
+    public var colors: [Color]
+    public init(colors: [Color]) { self.colors = colors }
+}
+
+/// A linear gradient fill, usable as a view.
+public struct LinearGradient: View {
+
+    internal let colors: [Color]
+    internal let startPoint: UnitPoint
+    internal let endPoint: UnitPoint
+
+    public init(colors: [Color], startPoint: UnitPoint, endPoint: UnitPoint) {
+        self.colors = colors
+        self.startPoint = startPoint
+        self.endPoint = endPoint
+    }
+
+    public init(gradient: Gradient, startPoint: UnitPoint, endPoint: UnitPoint) {
+        self.init(colors: gradient.colors, startPoint: startPoint, endPoint: endPoint)
+    }
+
+    public typealias Body = Never
+}
+
+extension LinearGradient: PrimitiveView {
+    public func _render(in context: ResolveContext) -> RenderNode {
+        RenderNode(type: "LinearGradient", id: context.path, props: [
+            "colors": .array(colors.map { $0.propValue }),
+            "startX": .double(startPoint.x), "startY": .double(startPoint.y),
+            "endX": .double(endPoint.x), "endY": .double(endPoint.y),
+        ])
+    }
+}