Add helpers for creating UI components.

mojo/ui/base_view.h

Index: mojo/ui/base_view.h
diff --git a/mojo/ui/base_view.h b/mojo/ui/base_view.h
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+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MOJO_UI_BASE_VIEW_H_
+#define MOJO_UI_BASE_VIEW_H_
+
+#include <string>
+
+#include "mojo/public/cpp/application/application_impl.h"
+#include "mojo/public/cpp/bindings/strong_binding.h"
+#include "mojo/public/cpp/system/macros.h"
+#include "mojo/public/interfaces/application/service_provider.mojom.h"
+#include "mojo/services/gfx/composition/interfaces/scenes.mojom.h"
+#include "mojo/services/ui/views/interfaces/view_manager.mojom.h"
+#include "mojo/services/ui/views/interfaces/view_provider.mojom.h"
+#include "mojo/services/ui/views/interfaces/views.mojom.h"
+
+namespace mojo {
+namespace ui {
+
+// Abstract base implementation of the View interface for simple applications.
+// Subclasses must handle layout and provide content for the scene by
+// implementing the methods of the |View| mojom interface.
+//
+// It is not necessary to use this class to implement all Views.
+// This class is merely intended to make the simple apps easier to write.
+class BaseView : public mojo::ui::View {
+ public:
+  // TODO(jeffbrown): Consider switching this over to an ApplicationConnector
+  // but having ApplicationImpl is handy for simple examples.
+  BaseView(
+      mojo::ApplicationImpl* app_impl,
+      const std::string& label,
+      const mojo::ui::ViewProvider::CreateViewCallback& create_view_callback);
+
+  ~BaseView() override;
+
+  // Gets the application implementation object provided at creation time.
+  mojo::ApplicationImpl* app_impl() { return app_impl_; }
+
+  // Gets the view manager.
+  mojo::ui::ViewManager* view_manager() { return view_manager_.get(); }
+
+  // Gets the view host for the view.
+  mojo::ui::ViewHost* view_host() { return view_host_.get(); }
+
+  // Gets the service provider for the view.
+  mojo::ServiceProvider* view_service_provider() {
+    return view_service_provider_.get();
+  }
+
+  // Gets the scene for the view.
+  // Returns nullptr if the |TakeScene| was called.
+  mojo::gfx::composition::Scene* scene() { return scene_.get(); }
+
+  // Takes the scene from the view.
+  // This is useful if the scene will be rendered by a separate component.
+  mojo::gfx::composition::ScenePtr TakeScene() { return scene_.Pass(); }
+
+  // |View|:
+  void OnChildUnavailable(uint32_t child_key,
+                          const OnChildUnavailableCallback& callback) override;
+
+ private:
+  mojo::ApplicationImpl* app_impl_;
+
+  mojo::StrongBinding<mojo::ui::View> view_binding_;
+  mojo::ui::ViewManagerPtr view_manager_;
+  mojo::ui::ViewHostPtr view_host_;
+  mojo::ServiceProviderPtr view_service_provider_;
+  mojo::gfx::composition::ScenePtr scene_;
+
+  MOJO_DISALLOW_COPY_AND_ASSIGN(BaseView);
+};
+
+}  // namespace ui
+}  // namespace mojo
+
+#endif  // MOJO_UI_BASE_VIEW_H_