Initial implementation of WebUI generator (WUG) toolkit.

components/webui_generator/view_model.h

+// 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 CHROME_BROWSER_UI_WEBUI_WUG_VIEW_MODEL_H_
+#define CHROME_BROWSER_UI_WEBUI_WUG_VIEW_MODEL_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "components/login/screens/screen_context.h"
+#include "components/webui_generator/export.h"
+
+namespace base {
+class DictionaryValue;
+}
+
+namespace webui_generator {
+
+using Context = login::ScreenContext;
+class View;
+
+// Base class for view-model. Usually View is responsible for creating and
+// initializing instances of this class.
+class WUG_EXPORT ViewModel {
+ public:
+  ViewModel();
+  virtual ~ViewModel();
+
+  void SetView(View* view);
+
+  // Called by view to notify that children are ready.
+  void OnChildrenReady();
+
+  // Called by view when it became bound (meaning that all changes in context
+  // will be reflected in view right after they are made).
+  virtual void OnViewBound() = 0;
+
+  // Notifies view-model about context changes happended on view side.
+  // View-model corrects its copy of context according to changes in |diff|.
+  void UpdateContext(const base::DictionaryValue& diff);
+
+  // Notifies view-model about |event| sent from view.
+  virtual void OnEvent(const std::string& event);
+
+ protected:
+  // Scoped context editor, which automatically commits all pending
+  // context changes on destruction.
+  class ContextEditor {
+   public:
+    using KeyType = ::login::ScreenContext::KeyType;
+    using String16List = ::login::String16List;
+    using StringList = ::login::StringList;
+
+    explicit ContextEditor(ViewModel& screen);
+    ~ContextEditor();
+
+    const ContextEditor& SetBoolean(const KeyType& key, bool value) const;
+    const ContextEditor& SetInteger(const KeyType& key, int value) const;
+    const ContextEditor& SetDouble(const KeyType& key, double value) const;
+    const ContextEditor& SetString(const KeyType& key,
+                                   const std::string& value) const;
+    const ContextEditor& SetString(const KeyType& key,
+                                   const base::string16& value) const;
+    const ContextEditor& SetStringList(const KeyType& key,
+                                       const StringList& value) const;
+    const ContextEditor& SetString16List(const KeyType& key,
+                                         const String16List& value) const;
+
+   private:
+    ViewModel& view_model_;
+    Context& context_;
+  };
+
+  // This method is called in a time appropriate for initialization. At this
+  // point it is allowed to make changes in the context, but it is not allowed
+  // to access child view-models.
+  virtual void Initialize() = 0;
+
+  // This method is called when all children are ready.
+  virtual void OnAfterChildrenReady() = 0;
+
+  // This method is called after context was changed on view side.
+  // |chanaged_keys| contains a list of keys of changed fields.
+  virtual void OnContextChanged(const std::vector<std::string>& changed_keys) {}
+
+  Context& context() { return context_; }
+  const Context& context() const { return context_; }
+
+  View* view() const { return view_; }
+
+  // Returns scoped context editor. The editor or it's copies should not outlive
+  // current BaseScreen instance.
+  ContextEditor GetContextEditor();
+
+  // Notifies view about changes made in context.
+  void CommitContextChanges();
+
+ private:
+  Context context_;
+  View* view_;
+
+  DISALLOW_COPY_AND_ASSIGN(ViewModel);
+};
+
+}  // namespace webui_generator
+
+#endif  // CHROME_BROWSER_UI_WEBUI_WUG_VIEW_MODEL_H_