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mojo/services/window_manager/basic_focus_rules.cc

+// 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.
+
+#include "mojo/services/window_manager/basic_focus_rules.h"
+
+#include "base/macros.h"
+#include "third_party/mojo_services/src/view_manager/public/cpp/view.h"
+
+using mojo::View;
+
+namespace window_manager {
+
+BasicFocusRules::BasicFocusRules(View* window_container)
+    : window_container_(window_container) {
+}
+
+BasicFocusRules::~BasicFocusRules() {}
+
+bool BasicFocusRules::SupportsChildActivation(View* view) const {
+  return true;
+}
+
+bool BasicFocusRules::IsToplevelView(View* view) const {
+  if (!IsViewParentedToWindowContainer(view))
+    return false;
+
+  // The window must exist within a container that supports activation.
+  // The window cannot be blocked by a modal transient.
+  return SupportsChildActivation(view->parent());
+}
+
+bool BasicFocusRules::CanActivateView(View* view) const {
+  if (!view)
+    return true;
+
+  // Only toplevel windows can be activated
+  if (!IsToplevelView(view))
+    return false;
+
+  // The view must be visible.
+  if (!view->visible())
+    return false;
+
+  // TODO(erg): The aura version of this class asks the aura::Window's
+  // ActivationDelegate whether the window is activatable.
+
+  // A window must be focusable to be activatable. We don't call
+  // CanFocusWindow() from here because it will call back to us via
+  // GetActivatableWindow().
+  if (!CanFocusViewImpl(view))
+    return false;
+
+  // TODO(erg): In the aura version, we also check whether the window is
+  // blocked by a modal transient window.
+
+  return true;
+}
+
+bool BasicFocusRules::CanFocusView(View* view) const {
+  // It is possible to focus a NULL window, it is equivalent to clearing focus.
+  if (!view)
+    return true;
+
+  // The focused view is always inside the active view, so views that aren't
+  // activatable can't contain the focused view.
+  View* activatable = GetActivatableView(view);
+  if (!activatable || !activatable->Contains(view))
+    return false;
+  return CanFocusViewImpl(view);
+}
+
+View* BasicFocusRules::GetToplevelView(View* view) const {
+  View* parent = view->parent();
+  View* child = view;
+  while (parent) {
+    if (IsToplevelView(child))
+      return child;
+
+    parent = parent->parent();
+    child = child->parent();
+  }
+
+  return nullptr;
+}
+
+View* BasicFocusRules::GetActivatableView(View* view) const {
+  View* parent = view->parent();
+  View* child = view;
+  while (parent) {
+    if (CanActivateView(child))
+      return child;
+
+    // TODO(erg): In the aura version of this class, we have a whole bunch of
+    // checks to support modal transient windows, and transient parents.
+
+    parent = parent->parent();
+    child = child->parent();
+  }
+
+  return nullptr;
+}
+
+View* BasicFocusRules::GetFocusableView(View* view) const {
+  if (CanFocusView(view))
+    return view;
+
+  // |view| may be in a hierarchy that is non-activatable, in which case we
+  // need to cut over to the activatable hierarchy.
+  View* activatable = GetActivatableView(view);
+  if (!activatable) {
+    // There may not be a related activatable hierarchy to cut over to, in which
+    // case we try an unrelated one.
+    View* toplevel = GetToplevelView(view);
+    if (toplevel)
+      activatable = GetNextActivatableView(toplevel);
+    if (!activatable)
+      return nullptr;
+  }
+
+  if (!activatable->Contains(view)) {
+    // If there's already a child window focused in the activatable hierarchy,
+    // just use that (i.e. don't shift focus), otherwise we need to at least cut
+    // over to the activatable hierarchy.
+    View* focused = GetFocusableView(activatable);
+    return activatable->Contains(focused) ? focused : activatable;
+  }
+
+  while (view && !CanFocusView(view))
+    view = view->parent();
+  return view;
+}
+
+View* BasicFocusRules::GetNextActivatableView(View* activatable) const {
+  DCHECK(activatable);
+
+  // In the basic scenarios handled by BasicFocusRules, the pool of activatable
+  // windows is limited to the |ignore|'s siblings.
+  const View::Children& siblings = activatable->parent()->children();
+  DCHECK(!siblings.empty());
+
+  for (auto rit = siblings.rbegin(); rit != siblings.rend(); ++rit) {
+    View* cur = *rit;
+    if (cur == activatable)
+      continue;
+    if (CanActivateView(cur))
+      return cur;
+  }
+  return nullptr;
+}
+
+// TODO(erg): aura::Window::CanFocus() exists. View::CanFocus() does
+// not. This is a hack that does everything that Window::CanFocus() currently
+// does that doesn't require a delegate or an EventClient.
+bool BasicFocusRules::CanFocusViewImpl(View* view) const {
+  // TODO(erg): In unit tests, views will never be drawn, so we can't rely on
+  // IsDrawn() here.
+  if (IsViewParentedToWindowContainer(view))
+    return view->visible();
+
+  // TODO(erg): Add the intermediary delegate and event client checks once we
+  // have those.
+
+  return CanFocusViewImpl(view->parent());
+}
+
+bool BasicFocusRules::IsViewParentedToWindowContainer(View* view) const {
+  return view->parent() == window_container_;
+}
+
+}  // namespace mojo