Add BodyAccessor featuere (#60)

* Update hostPreferenceValues

And connect the output with the graph

* Add ViewBodyAccessor

* Add AppBodyAccessor

Author: Kyle-Ye

Example/HostingExample/ViewController.swift

@@ -21,6 +21,6 @@ class ViewController: UINavigationController {
 
 struct ContentView: View {
     var body: some View {
-        EmptyView()
+        AnyView(EmptyView())
     }
 }

Package.resolved

@@ -7,7 +7,7 @@
       "location" : "https://github.com/OpenSwiftUIProject/OpenGraph",
       "state" : {
         "branch" : "main",
-        "revision" : "c952860989b69c4537146b323c0ec1cb3f8fb206"
+        "revision" : "315468c6339cdbcbaf7d8797b866745d5bf11d8e"
       }
     },
     {

Sources/OpenSwiftUI/App/App.swift

@@ -93,7 +93,7 @@ public protocol App {
     /// Swift infers the app's ``OpenSwiftUI/App/Body-swift.associatedtype``
     /// associated type based on the scene provided by the `body` property.
     @SceneBuilder
-    @MainActor
+    @MainActor(unsafe)
     var body: Self.Body { get }
 
     /// Creates an instance of the app using the body that you define for its
@@ -102,7 +102,7 @@ public protocol App {
     /// Swift synthesizes a default initializer for structures that don't
     /// provide one. You typically rely on the default initializer for
     /// your app.
-    @MainActor
+    @MainActor(unsafe)
     init()
 }
 
@@ -115,7 +115,7 @@ extension App {
     /// the app. OpenSwiftUI provides a
     /// default implementation of the method that manages the launch process in
     /// a platform-appropriate way.
-    @MainActor
+    @MainActor(unsafe)
     public static func main() {
         let app = Self()
         runApp(app)

Sources/OpenSwiftUI/App/AppGraph.swift

@@ -65,3 +65,16 @@ final class AppGraph: GraphHost {
         }
     }
 }
+
+private struct AppBodyAccessor<Container: App>: BodyAccessor {
+    typealias Body = Container.Body
+    
+    func updateBody(of container: Container, changed: Bool) {
+        guard changed else {
+            return
+        }
+        setBody {
+            container.body
+        }
+    }
+}

Sources/OpenSwiftUI/Core/BodyAccessor/BodyAccessor.swift

@@ -5,8 +5,21 @@
 //  Audited for RELEASE_2021
 //  Status: Complete
 
+internal import OpenGraphShims
+
 protocol BodyAccessor<Container, Body> {
     associatedtype Container
     associatedtype Body
     func updateBody(of: Container, changed: Bool)
 }
+
+extension BodyAccessor {
+    func setBody(_ body: () -> Body) {
+        let value = traceRuleBody(Container.self) {
+            OGGraph.withoutUpdate(body)
+        }
+        withUnsafePointer(to: value) { value in
+            OGGraph.setOutputValue(value)
+        }
+    }
+}

Sources/OpenSwiftUI/Core/BodyAccessor/ViewBodyAccessor.swift

@@ -3,15 +3,17 @@
 //  OpenSwiftUI
 //
 //  Audited for RELEASE_2021
-//  Status: WIP
+//  Status: Complete
 
 struct ViewBodyAccessor<Container: View>: BodyAccessor {
     typealias Body = Container.Body
 
-    func updateBody(of: Container, changed: Bool) {
+    func updateBody(of container: Container, changed: Bool) {
         guard changed else {
             return
         }
-        // TODO
+        setBody {
+            container.body
+        }
     }
 }

Sources/OpenSwiftUI/Core/Log/Signpost.swift

@@ -6,6 +6,7 @@
 //  Status: WIP
 //  ID: 34756F646CF7AC3DBE2A8E0B344C962F
 
+internal import OpenGraphShims
 #if canImport(os)
 import os.signpost
 #endif
@@ -26,7 +27,37 @@ struct Signpost {
 
     static let render = Signpost(style: .kdebug(0), stability: .published)
     static let renderUpdate = Signpost(style: .kdebug(0), stability: .published)
-    static let viewHost = Signpost(style: .kdebug(0), stability: .published)
+    static let viewHost = Signpost(style: .kdebug(9), stability: .published)
+    static let bodyInvoke = Signpost(style: .kdebug(5), stability: .published)
+    
+    @_transparent
+    @inline(__always)
+    func traceInterval<R>(
+        object: AnyObject? = nil,
+        _ message: StaticString?,
+        closure: () -> R
+    ) -> R {
+        guard isEnabled else {
+            return closure()
+        }
+        // TODO
+        return closure()
+    }
+    
+    @_transparent
+    @inline(__always)
+    func traceInterval<R>(
+        object: AnyObject? = nil,
+        _ message: StaticString?,
+        _ arguments: @autoclosure () -> [CVarArg],
+        closure: () -> R
+    ) -> R {
+        guard isEnabled else {
+            return closure()
+        }
+        // TODO
+        return closure()
+    }
 }
 
 extension Signpost {
@@ -43,4 +74,14 @@ extension Signpost {
     }
 }
 
-
+@_transparent
+@inline(__always)
+// FIXME
+func traceRuleBody<R>(_ type: Any.Type, body: () -> R) -> R {
+    Signpost.bodyInvoke.traceInterval(
+        "%{public}@.body [in %{public}@]",
+        [OGTypeID(type).description, Tracing.libraryName(defining: type)]
+    ) {
+        body()
+    }
+}

Sources/OpenSwiftUI/Core/View/View.swift

@@ -71,7 +71,7 @@ public protocol View {
     /// For more information about composing views and a view hierarchy,
     /// see <doc:Declaring-a-Custom-View>.
     @ViewBuilder
-    @MainActor
+    @MainActor(unsafe)
     var body: Self.Body { get }
 }
 

Sources/OpenSwiftUI/Core/View/ViewGraph.swift

@@ -229,6 +229,7 @@ final class ViewGraph: GraphHost {
             rootGeometry.$childLayoutComputer = outputs.$layoutComputer
         }
         // TODO
+        hostPreferenceValues.projectedValue = outputs.hostPreferences
         makePreferenceOutlets(outputs: outputs)
         #endif
     }

Sources/OpenSwiftUI/Data/Preference/HostPreferencesKey.swift

@@ -6,6 +6,8 @@
 //  Status: Complete
 //  ID: 7429200566949B8FB892A77E01A988C8
 
+internal import OpenGraphShims
+
 struct HostPreferencesKey: PreferenceKey {
     static var defaultValue: PreferenceList {
         PreferenceList()
@@ -25,3 +27,19 @@ extension HostPreferencesKey {
         return nodeId
     }
 }
+
+extension _ViewOutputs {
+    @inline(__always)
+    var hostPreferences: Attribute<PreferenceList>? {
+        get { self[HostPreferencesKey.self] }
+        set { self[HostPreferencesKey.self] = newValue }
+    }
+}
+
+extension PreferencesOutputs {
+    @inline(__always)
+    var hostPreferences: Attribute<PreferenceList>? {
+        get { self[HostPreferencesKey.self] }
+        set { self[HostPreferencesKey.self] = newValue }
+    }
+}

Sources/OpenSwiftUI/Data/Preference/PreferenceBridge.swift

@@ -173,7 +173,7 @@ final class PreferenceBridge {
                     values: OptionalAttribute(base: AnyOptionalAttribute(outputs[anyKey: key])),
                     children: []
                 ))
-                outputs[anyKey: key] = combiner.identifier
+                outputs.hostPreferences = combiner
                 $hostPreferenceKeys = inputs.preferences.hostKeys
                 $hostPreferencesCombiner = combiner
             } else {