Support <meta>/<title> in Fiber renderers

Sources/TokamakCore/App/Scenes/WindowGroup.swift

@@ -15,6 +15,11 @@
 //  Created by Carson Katri on 7/16/20.
 //
 
+@_spi(TokamakCore)
+public struct _WindowGroupTitle: _PrimitiveView {
+  public let title: Text?
+}
+
 public struct WindowGroup<Content>: Scene, TitledScene where Content: View {
   public let id: String
   public let title: Text?
@@ -77,6 +82,9 @@ public struct WindowGroup<Content>: Scene, TitledScene where Content: View {
 //  }
 
   public func _visitChildren<V>(_ visitor: V) where V: SceneVisitor {
-    visitor.visit(content)
+    visitor.visit(Group {
+      _WindowGroupTitle(title: self.title)
+      content
+    })
   }
 }

Sources/TokamakCore/Fiber/Fiber+CustomDebugStringConvertible.swift

@@ -29,7 +29,7 @@ extension FiberReconciler.Fiber: CustomDebugStringConvertible {
   private func flush(level: Int = 0) -> String {
     let spaces = String(repeating: " ", count: level)
     let geometry = geometry ?? .init(
-      origin: .init(origin: .zero),
+      origin: .init(parent: .zero, origin: .zero),
       dimensions: .init(size: .zero, alignmentGuides: [:]),
       proposal: .unspecified
     )

Sources/TokamakCore/Fiber/Fiber.swift

@@ -423,7 +423,8 @@ public extension FiberReconciler {
           environment: .init(rootEnvironment),
           traits: .init(),
           preferenceStore: preferences
-        )
+        ),
+        preferenceStore: preferences ?? .init()
       )
       if let preferenceStore = outputs.preferenceStore {
         preferences = preferenceStore

Sources/TokamakCore/Fiber/FiberReconciler.swift

@@ -41,15 +41,13 @@ public final class FiberReconciler<Renderer: FiberRenderer> {
 
   private var sceneSizeCancellable: AnyCancellable?
 
-  private var isReconciling = false
   /// The identifiers for each `Fiber` that changed state during the last run loop.
   ///
   /// The reconciler loop starts at the root of the `View` hierarchy
   /// to ensure all preference values are passed down correctly.
   /// To help mitigate performance issues related to this, we only perform reconcile
   /// checks when we reach a changed `Fiber`.
   private var changedFibers = Set<ObjectIdentifier>()
-  public var afterReconcileActions = [() -> ()]()
 
   struct RootView<Content: View>: View {
     let content: Content
@@ -59,7 +57,6 @@ public final class FiberReconciler<Renderer: FiberRenderer> {
       var environment = reconciler.renderer.defaultEnvironment
       environment.measureText = reconciler.renderer.measureText
       environment.measureImage = reconciler.renderer.measureImage
-      environment.afterReconcile = reconciler.afterReconcile
       return environment
     }
 
@@ -69,6 +66,10 @@ public final class FiberReconciler<Renderer: FiberRenderer> {
           .environmentValues(environment)
       }
     }
+
+    static func _makeView(_ inputs: ViewInputs<Self>) -> ViewOutputs {
+      .init(inputs: inputs, preferenceStore: inputs.preferenceStore ?? .init())
+    }
   }
 
   /// The `Layout` container for the root of a `View` hierarchy.
@@ -140,7 +141,6 @@ public final class FiberReconciler<Renderer: FiberRenderer> {
     var environment = renderer.defaultEnvironment
     environment.measureText = renderer.measureText
     environment.measureImage = renderer.measureImage
-    environment.afterReconcile = afterReconcile
     var app = app
     current = .init(
       &app,
@@ -215,15 +215,6 @@ public final class FiberReconciler<Renderer: FiberRenderer> {
     }
   }
 
-  func afterReconcile(_ action: @escaping () -> ()) {
-    guard isReconciling == true
-    else {
-      action()
-      return
-    }
-    afterReconcileActions.append(action)
-  }
-
   /// Called by any `Fiber` that experiences a state change.
   ///
   /// Reconciliation only runs after every change during the current run loop has been performed.
@@ -243,7 +234,6 @@ public final class FiberReconciler<Renderer: FiberRenderer> {
   ///
   /// A `reconcile()` call is queued from `fiberChanged` once per run loop.
   func reconcile() {
-    isReconciling = true
     let changedFibers = changedFibers
     self.changedFibers.removeAll()
     // Create a list of mutations.
@@ -270,21 +260,8 @@ public final class FiberReconciler<Renderer: FiberRenderer> {
     self.alternate = current
     current = alternate
 
-    isReconciling = false
-
-    for action in afterReconcileActions {
-      action()
+    if let preferences = current.preferences {
+      renderer.preferencesChanged(preferences)
     }
   }
 }
-
-public extension EnvironmentValues {
-  private enum AfterReconcileKey: EnvironmentKey {
-    static let defaultValue: (@escaping () -> ()) -> () = { _ in }
-  }
-
-  var afterReconcile: (@escaping () -> ()) -> () {
-    get { self[AfterReconcileKey.self] }
-    set { self[AfterReconcileKey.self] = newValue }
-  }
-}

Sources/TokamakCore/Fiber/FiberRenderer.swift

@@ -88,6 +88,9 @@ public protocol FiberRenderer {
   /// (in this case just `DuelOfTheStates` as both properties were on it),
   /// and reconcile after all changes have been collected.
   func schedule(_ action: @escaping () -> ())
+
+  /// Called by the reconciler when the preferences of the topmost `Fiber` changed.
+  func preferencesChanged(_ preferenceStore: _PreferenceStore)
 }
 
 public extension FiberRenderer {
@@ -107,6 +110,8 @@ public extension FiberRenderer {
     }
   }
 
+  func preferencesChanged(_ preferenceStore: _PreferenceStore) {}
+
   @discardableResult
   @_disfavoredOverload
   func render<V: View>(_ view: V) -> FiberReconciler<Self> {

Sources/TokamakCore/Fiber/Layout/LayoutSubviews.swift

@@ -22,15 +22,20 @@ public struct LayoutSubviews: Equatable, RandomAccessCollection {
   public var layoutDirection: LayoutDirection
   var storage: [LayoutSubview]
 
-  init(layoutDirection: LayoutDirection, storage: [LayoutSubview]) {
+  @_spi(TokamakCore)
+  public var globalOrigin: CGPoint
+
+  init(layoutDirection: LayoutDirection, storage: [LayoutSubview], globalOrigin: CGPoint) {
     self.layoutDirection = layoutDirection
     self.storage = storage
+    self.globalOrigin = globalOrigin
   }
 
   init<R: FiberRenderer>(_ node: FiberReconciler<R>.Fiber) {
     self.init(
       layoutDirection: node.outputs.environment.environment.layoutDirection,
-      storage: []
+      storage: [],
+      globalOrigin: node.geometry?.origin.globalOrigin ?? .zero
     )
   }
 
@@ -53,15 +58,20 @@ public struct LayoutSubviews: Equatable, RandomAccessCollection {
   }
 
   public subscript(bounds: Range<Int>) -> LayoutSubviews {
-    .init(layoutDirection: layoutDirection, storage: .init(storage[bounds]))
+    .init(
+      layoutDirection: layoutDirection,
+      storage: .init(storage[bounds]),
+      globalOrigin: globalOrigin
+    )
   }
 
   public subscript<S>(indices: S) -> LayoutSubviews where S: Sequence, S.Element == Int {
     .init(
       layoutDirection: layoutDirection,
       storage: storage.enumerated()
         .filter { indices.contains($0.offset) }
-        .map(\.element)
+        .map(\.element),
+      globalOrigin: globalOrigin
     )
   }
 }
@@ -165,17 +175,24 @@ public struct LayoutSubview: Equatable {
       guard let fiber = fiber, let element = element else { return }
       let geometry = ViewGeometry(
         // Shift to the anchor point in the parent's coordinate space.
-        origin: .init(origin: .init(
-          x: position.x - (dimensions.width * anchor.x),
-          y: position.y - (dimensions.height * anchor.y)
-        )),
+        origin: .init(
+          parent: fiber.elementParent?.geometry?.origin.globalOrigin ?? .zero,
+          origin: .init(
+            x: position.x - (dimensions.width * anchor.x),
+            y: position.y - (dimensions.height * anchor.y)
+          )
+        ),
         dimensions: dimensions,
         proposal: proposal
       )
       // Push a layout mutation if needed.
       if geometry != fiber.alternate?.geometry {
         caches.mutations.append(.layout(element: element, geometry: geometry))
       }
+      caches.layoutSubviews[
+        ObjectIdentifier(fiber),
+        default: .init(fiber)
+      ].globalOrigin = geometry.origin.globalOrigin
       // Update ours and our alternate's geometry
       fiber.geometry = geometry
       fiber.alternate?.geometry = geometry

Sources/TokamakCore/Fiber/Passes/ReconcilePass.swift

@@ -251,7 +251,7 @@ struct ReconcilePass: FiberReconcilerPass {
           previous: element,
           newContent: newContent,
           geometry: node.fiber?.geometry ?? .init(
-            origin: .init(origin: .zero),
+            origin: .init(parent: .zero, origin: .zero),
             dimensions: .init(size: .zero, alignmentGuides: [:]),
             proposal: .unspecified
           )

Sources/TokamakCore/Fiber/ViewGeometry.swift

@@ -29,13 +29,20 @@ public struct ViewGeometry: Equatable {
 
 /// The position of the `View` relative to its parent.
 public struct ViewOrigin: Equatable {
+  @_spi(TokamakCore)
+  public let parent: CGPoint
+
   @_spi(TokamakCore)
   public let origin: CGPoint
 
   @_spi(TokamakCore)
   public var x: CGFloat { origin.x }
   @_spi(TokamakCore)
   public var y: CGFloat { origin.y }
+
+  public var globalOrigin: CGPoint {
+    parent.offset(by: origin)
+  }
 }
 
 public struct ViewDimensions: Equatable {

Sources/TokamakCore/Preferences/PreferenceKey.swift

@@ -118,6 +118,19 @@ public final class _PreferenceStore: CustomDebugStringConvertible {
     _PreferenceValue(storage: previousValues[ObjectIdentifier(key)] ?? .init(key))
   }
 
+  /// Returns the new value for `Key`, or `nil` if the value did not change.
+  public func newValue<Key>(forKey key: Key.Type = Key.self) -> Key.Value?
+    where Key: PreferenceKey, Key.Value: Equatable
+  {
+    let value = value(forKey: key).value
+    let previousValue = previousValue(forKey: key).value
+    if value != previousValue {
+      return value
+    } else {
+      return nil
+    }
+  }
+
   public func insert<Key>(_ value: Key.Value, forKey key: Key.Type = Key.self)
     where Key: PreferenceKey
   {

Sources/TokamakDOM/DOMFiberRenderer.swift

@@ -225,9 +225,7 @@ public struct DOMFiberRenderer: FiberRenderer {
         src: bundle?
           .path(forResource: name, ofType: nil) ?? name
       ) { naturalSize in
-        environment.afterReconcile {
-          image._intrinsicSize = naturalSize
-        }
+        image._intrinsicSize = naturalSize
       }
       return .zero
     case let .resizable(.named(name, bundle: bundle), _, _):
@@ -239,9 +237,7 @@ public struct DOMFiberRenderer: FiberRenderer {
           src: bundle?
             .path(forResource: name, ofType: nil) ?? name
         ) { naturalSize in
-          environment.afterReconcile {
-            image._intrinsicSize = naturalSize
-          }
+          image._intrinsicSize = naturalSize
         }
         return .zero
       }
@@ -323,6 +319,38 @@ public struct DOMFiberRenderer: FiberRenderer {
     }
   }
 
+  final class Head {
+    let head = document.head.object!
+    var metaTags = [JSObject]()
+    var title: JSObject?
+  }
+
+  private let head = Head()
+  public func preferencesChanged(_ preferenceStore: _PreferenceStore) {
+    if let newMetaTags = preferenceStore.newValue(forKey: HTMLMetaPreferenceKey.self) {
+      for oldTag in head.metaTags {
+        _ = head.head.removeChild!(oldTag)
+      }
+      head.metaTags = newMetaTags.map {
+        let template = document.createElement!("template").object!
+        template.innerHTML = .string($0.outerHTML())
+        let meta = template.content.firstChild.object!
+        _ = head.head.appendChild!(meta)
+        return meta
+      }
+    }
+    if let newTitle = preferenceStore.newValue(forKey: HTMLTitlePreferenceKey.self) {
+      if let title = head.title {
+        title.innerHTML = .string(newTitle)
+      } else {
+        let node = document.createElement!("title").object!
+        _ = head.head.appendChild!(node)
+        node.innerHTML = .string(newTitle)
+        head.title = node
+      }
+    }
+  }
+
   private let scheduler = JSScheduler()
   public func schedule(_ action: @escaping () -> ()) {
     scheduler.schedule(options: nil, action)