Reimplement padding modifiers under new layout system

Author: stackotter

Sources/SwiftCrossUI/Modifiers/Padding.swift

@@ -1,42 +1,73 @@
-// extension View {
-//     /// Adds a specific padding amount to each edge of this view.
-//     public func padding(_ amount: Int) -> some View {
-//         return PaddingModifierView(body: VariadicView1(self), edges: .all, padding: amount)
-//     }
-
-//     /// Adds an equal padding amount to specific edges of this view.
-//     public func padding(_ edges: Edge.Set, _ amount: Int) -> some View {
-//         return PaddingModifierView(body: VariadicView1(self), edges: edges, padding: amount)
-//     }
-// }
-
-// /// The implementation for the ``View/padding(_:_:)`` and ``View/padding(_:)`` view modifiers.
-// struct PaddingModifierView<Child: View>: TypeSafeView {
-//     var body: VariadicView1<Child>
-
-//     /// The edges on which to apply padding.
-//     var edges: Edge.Set
-//     /// The amount of padding to apply to the child view.
-//     var padding: Int
-
-//     func asWidget<Backend: AppBackend>(
-//         _ children: ViewGraphNodeChildren1<Child>,
-//         backend: Backend
-//     ) -> Backend.Widget {
-//         return backend.createPaddingContainer(for: children.child0.widget.into())
-//     }
-
-//     func update<Backend: AppBackend>(
-//         _ container: Backend.Widget,
-//         children: ViewGraphNodeChildren1<Child>,
-//         backend: Backend
-//     ) {
-//         backend.setPadding(
-//             ofPaddingContainer: container,
-//             top: edges.contains(.top) ? padding : 0,
-//             bottom: edges.contains(.bottom) ? padding : 0,
-//             leading: edges.contains(.leading) ? padding : 0,
-//             trailing: edges.contains(.trailing) ? padding : 0
-//         )
-//     }
-// }
+extension View {
+    /// Adds a specific padding amount to each edge of this view.
+    public func padding(_ amount: Int) -> some View {
+        return PaddingModifierView(body: VariadicView1(self), edges: .all, padding: amount)
+    }
+
+    /// Adds an equal padding amount to specific edges of this view.
+    public func padding(_ edges: Edge.Set, _ amount: Int) -> some View {
+        return PaddingModifierView(body: VariadicView1(self), edges: edges, padding: amount)
+    }
+}
+
+/// The implementation for the ``View/padding(_:_:)`` and ``View/padding(_:)`` view modifiers.
+struct PaddingModifierView<Child: View>: TypeSafeView {
+    var body: VariadicView1<Child>
+
+    /// The edges on which to apply padding.
+    var edges: Edge.Set
+    /// The amount of padding to apply to the child view.
+    var padding: Int
+
+    public var flexibility: Int {
+        body.flexibility - 10
+    }
+
+    func children<Backend: AppBackend>(
+        backend: Backend,
+        snapshots: [ViewGraphSnapshotter.NodeSnapshot]?,
+        environment: Environment
+    ) -> ViewGraphNodeChildren1<Child> {
+        body.children(backend: backend, snapshots: snapshots, environment: environment)
+    }
+
+    func asWidget<Backend: AppBackend>(
+        _ children: ViewGraphNodeChildren1<Child>,
+        backend: Backend
+    ) -> Backend.Widget {
+        let container = backend.createContainer()
+        backend.addChild(children.child0.widget.into(), to: container)
+        return container
+    }
+
+    func update<Backend: AppBackend>(
+        _ container: Backend.Widget,
+        children: ViewGraphNodeChildren1<Child>,
+        proposedSize: SIMD2<Int>,
+        environment: Environment,
+        backend: Backend
+    ) -> SIMD2<Int> {
+        let topPadding = edges.contains(.top) ? padding : 0
+        let bottomPadding = edges.contains(.bottom) ? padding : 0
+        let leadingPadding = edges.contains(.leading) ? padding : 0
+        let trailingPadding = edges.contains(.trailing) ? padding : 0
+
+        let childSize = children.child0.update(
+            with: body.view0,
+            proposedSize: SIMD2(
+                proposedSize.x - leadingPadding - trailingPadding,
+                proposedSize.y - topPadding - bottomPadding
+            ),
+            environment: environment
+        )
+
+        let size = SIMD2(
+            childSize.x + leadingPadding + trailingPadding,
+            childSize.y + topPadding + bottomPadding
+        )
+        backend.setSize(of: container, to: size)
+        backend.setPosition(ofChildAt: 0, in: container, to: SIMD2(topPadding, leadingPadding))
+
+        return size
+    }
+}