Reland: Remove aura and make a pure mojo::View version of FocusController.

mojo/services/window_manager/focus_rules.h

+// Copyright 2014 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_SERIVCES_WINDOW_MANAGER_FOCUS_RULES_H_
+#define MOJO_SERIVCES_WINDOW_MANAGER_FOCUS_RULES_H_
+
+#include "mojo/services/public/cpp/view_manager/types.h"
+#include "mojo/services/public/cpp/view_manager/view.h"
+
+namespace mojo {
+
+// Implemented by an object that establishes the rules about what can be
+// focused or activated.
+class FocusRules {
+ public:
+  virtual ~FocusRules() {}
+
+  // Returns true if |view| is a toplevel view. Whether or not a view
+  // is considered toplevel is determined by a similar set of rules that
+  // govern activation and focus. Not all toplevel views are activatable,
+  // call CanActivateView() to determine if a view can be activated.
+  virtual bool IsToplevelView(View* view) const = 0;
+  // Returns true if |view| can be activated or focused.
+  virtual bool CanActivateView(View* view) const = 0;
+  // For CanFocusView(), null is supported, because null is a valid focusable
+  // view (in the case of clearing focus).
+  virtual bool CanFocusView(View* view) const = 0;
+
+  // Returns the toplevel view containing |view|. Not all toplevel views
+  // are activatable, call GetActivatableView() instead to return the
+  // activatable view, which might be in a different hierarchy.
+  // Will return null if |view| is not contained by a view considered to be
+  // a toplevel view.
+  virtual View* GetToplevelView(View* view) const = 0;
+  // Returns the activatable or focusable view given an attempt to activate or
+  // focus |view|. Some possible scenarios (not intended to be exhaustive):
+  // - |view| is a child of a non-focusable view and so focus must be set
+  //   according to rules defined by the delegate, e.g. to a parent.
+  // - |view| is an activatable view that is the transient parent of a modal
+  //   view, so attempts to activate |view| should result in the modal
+  //   transient being activated instead.
+  // These methods may return null if they are unable to find an activatable
+  // or focusable view given |view|.
+  virtual View* GetActivatableView(View* view) const = 0;
+  virtual View* GetFocusableView(View* view) const = 0;
+
+  // Returns the next view to activate in the event that |ignore| is no longer
+  // activatable. This function is called when something is happening to
+  // |ignore| that means it can no longer have focus or activation, including
+  // but not limited to:
+  // - it or its parent hierarchy is being hidden, or removed from the
+  //   RootView.
+  // - it is being destroyed.
+  // - it is being explicitly deactivated.
+  // |ignore| cannot be null.
+  virtual View* GetNextActivatableView(View* ignore) const = 0;
+};
+
+}  // namespace mojo
+
+#endif  // MOJO_SERIVCES_WINDOW_MANAGER_FOCUS_RULES_H_