Remove `DefaultApp`, make `DOMRenderer` internal (#227)

Removes the `View`-based initializer of `DOMRenderer` which no longer leaves any `public` initializers on it, means we can make it fully internal. `DOMNode` is now internal too, which is great as it was an implementation detail anyway. Corollary, `DefaultApp` is no longer needed.

`Target` was cleaned up is it doesn't need to hold `App` or `Scene` values, now it's just a simple protocol.

I've updated `README.md` to show usage of the `App` protocol in the basic example.

Closes #224.

README.md

@@ -48,23 +48,18 @@ struct Counter: View {
     }
   }
 }
-```
 
-You can then render your view in any DOM node captured with
-[JavaScriptKit](https://github.com/kateinoigakukun/JavaScriptKit/), just
-pass it as an argument to the `DOMRenderer` initializer together with your view:
+struct CounterApp: App {
+  var body: some Scene {
+    WindowGroup("Counter Demo") {
+      Counter(count: 5, limit: 15)
+    }
+  }
+}
 
-```swift
-import JavaScriptKit
-import TokamakDOM
-
-let document = JSObjectRef.global.document.object!
-
-let divElement = document.createElement!("div").object!
-let renderer = DOMRenderer(Counter(count: 5, limit: 15), divElement)
-
-let body = document.body.object!
-_ = body.appendChild!(divElement)
+// @main attribute is not supported in SwiftPM apps.
+// See https://bugs.swift.org/browse/SR-12683 for more details.
+CounterApp.main()
 ```
 
 ### Arbitrary HTML

Sources/TokamakCore/Target.swift

@@ -15,52 +15,6 @@
 //  Created by Max Desiatov on 10/02/2019.
 //
 
-open class Target {
-  var element: MountedElementKind
-  public internal(set) var app: _AnyApp {
-    get {
-      if case let .app(app) = element {
-        return app
-      } else {
-        fatalError("`Target` has type \(element) not `App`")
-      }
-    }
-    set {
-      element = .app(newValue)
-    }
-  }
-
-  public internal(set) var scene: _AnyScene {
-    get {
-      if case let .scene(scene) = element {
-        return scene
-      } else {
-        fatalError("`Target` has type \(element) not `Scene`")
-      }
-    }
-    set {
-      element = .scene(newValue)
-    }
-  }
-
-  public internal(set) var view: AnyView {
-    get {
-      if case let .view(view) = element {
-        return view
-      } else {
-        fatalError("`Target` has type \(element) not `View`")
-      }
-    }
-    set {
-      element = .view(newValue)
-    }
-  }
-
-  public init<V: View>(_ view: V) {
-    element = .view(AnyView(view))
-  }
-
-  public init<A: App>(_ app: A) {
-    element = .app(_AnyApp(app))
-  }
+public protocol Target: AnyObject {
+  var view: AnyView { get set }
 }

Sources/TokamakDOM/App.swift

@@ -72,13 +72,3 @@ extension App {
     ScenePhaseObserver.publisher
   }
 }
-
-struct DefaultApp<V: View>: App {
-  var content: V?
-
-  var body: some Scene {
-    WindowGroup {
-      content
-    }
-  }
-}

Sources/TokamakDOM/DOMNode.swift

@@ -15,22 +15,22 @@
 import JavaScriptKit
 import TokamakCore
 
-public final class DOMNode: Target {
+final class DOMNode: Target {
   let ref: JSObjectRef
   private var listeners: [String: JSClosure]
+  var view: AnyView
 
   init<V: View>(_ view: V, _ ref: JSObjectRef, _ listeners: [String: Listener] = [:]) {
     self.ref = ref
     self.listeners = [:]
-    super.init(view)
+    self.view = AnyView(view)
     reinstall(listeners)
   }
 
-  init<A: App>(_ app: A, _ ref: JSObjectRef, _ listeners: [String: Listener] = [:]) {
+  init(_ ref: JSObjectRef) {
     self.ref = ref
-    self.listeners = [:]
-    super.init(app)
-    reinstall(listeners)
+    view = AnyView(EmptyView())
+    listeners = [:]
   }
 
   /// Removes all existing event listeners on this DOM node and install new ones from

Sources/TokamakDOM/DOMRenderer.swift

@@ -74,33 +74,25 @@ func appendRootStyle(_ rootNode: JSObjectRef) {
   _ = head.appendChild!(rootStyle)
 }
 
-public final class DOMRenderer: Renderer {
-  public private(set) var reconciler: StackReconciler<DOMRenderer>?
+final class DOMRenderer: Renderer {
+  private(set) var reconciler: StackReconciler<DOMRenderer>?
 
   private let rootRef: JSObjectRef
 
-  public convenience init<V: View>(
-    _ view: V,
-    _ ref: JSObjectRef,
-    _ rootEnvironment: EnvironmentValues? = nil
-  ) {
-    self.init(DefaultApp(content: view), ref, rootEnvironment)
-  }
-
   init<A: App>(_ app: A, _ ref: JSObjectRef, _ rootEnvironment: EnvironmentValues? = nil) {
     rootRef = ref
     appendRootStyle(ref)
 
     reconciler = StackReconciler(
       app: app,
-      target: DOMNode(app, ref),
+      target: DOMNode(ref),
       environment: .defaultEnvironment,
       renderer: self,
       scheduler: timeoutScheduler
     )
   }
 
-  public func mountTarget(to parent: DOMNode, with host: MountedHost) -> DOMNode? {
+  func mountTarget(to parent: DOMNode, with host: MountedHost) -> DOMNode? {
     guard let (outerHTML, listeners) = mapAnyView(
       host.view,
       transform: { (html: AnyHTML) in (html.outerHTML, html.listeners) }
@@ -133,14 +125,14 @@ public final class DOMRenderer: Renderer {
     return DOMNode(host.view, lastChild, listeners)
   }
 
-  public func update(target: DOMNode, with host: MountedHost) {
+  func update(target: DOMNode, with host: MountedHost) {
     guard let html = mapAnyView(host.view, transform: { (html: AnyHTML) in html })
     else { return }
 
     html.update(dom: target)
   }
 
-  public func unmount(
+  func unmount(
     target: DOMNode,
     from parent: DOMNode,
     with host: MountedHost,