Implementing answer card hover highlight.

ui/app_list/views/search_result_answer_card_view.cc

 // Copyright 2017 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 "ui/app_list/views/search_result_answer_card_view.h"
 
 #include "ui/app_list/app_list_constants.h"
 #include "ui/app_list/app_list_features.h"
 #include "ui/app_list/app_list_view_delegate.h"
+#include "ui/app_list/search_result_observer.h"
 #include "ui/views/background.h"
 #include "ui/views/controls/button/custom_button.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/layout/fill_layout.h"
 
 namespace app_list {
 
 // Container of the search answer view.
 class SearchResultAnswerCardView::SearchAnswerContainerView
     : public views::CustomButton,
-      public views::ButtonListener {
+      public views::ButtonListener,
+      public SearchResultObserver {
  public:
   explicit SearchAnswerContainerView(AppListViewDelegate* view_delegate)
       : CustomButton(this), view_delegate_(view_delegate) {
     // Center the card horizontally in the container.
     views::BoxLayout* answer_container_layout =
         new views::BoxLayout(views::BoxLayout::kHorizontal, 0, 0, 0);
     answer_container_layout->set_main_axis_alignment(
         views::BoxLayout::MAIN_AXIS_ALIGNMENT_CENTER);
     SetLayoutManager(answer_container_layout);
     SetVisible(false);
@@ skipping 11 matching lines @@
     views::View* const new_result_view =
         search_result ? search_result->view() : nullptr;
 
     if (old_result_view != new_result_view) {
       if (old_result_view != nullptr)
         RemoveChildView(old_result_view);
       if (new_result_view != nullptr)
         AddChildView(new_result_view);
     }
 
+    if (search_result_)
+      search_result_->RemoveObserver(this);
     search_result_ = search_result ? search_result->Duplicate() : nullptr;
+    if (search_result_)
+      search_result_->AddObserver(this);
 
     SetVisible(new_result_view != nullptr);
   }
 
   // views::CustomButton overrides:
   const char* GetClassName() const override {
     return "SearchAnswerContainerView";
   }
 
   void StateChanged(ButtonState old_state) override { UpdateBackgroundColor(); }
 
   // views::ButtonListener overrides:
   void ButtonPressed(views::Button* sender, const ui::Event& event) override {
     DCHECK(sender == this);
     DCHECK(search_result_);
     view_delegate_->OpenSearchResult(search_result_.get(), false,
                                      event.flags());
   }
 
+  // SearchResultObserver overrides:
+  void OnViewHoverStateChanged() override { UpdateBackgroundColor(); }
+
  private:
   void UpdateBackgroundColor() {
-    if (selected_)
+    if (selected_) {
       SetBackground(views::CreateSolidBackground(kSelectedColor));
-    else if (state() == STATE_HOVERED || state() == STATE_PRESSED)
+    } else if (state() == STATE_HOVERED || state() == STATE_PRESSED ||
+               (search_result_ && search_result_->is_mouse_in_view())) {
       SetBackground(views::CreateSolidBackground(kHighlightedColor));
+    } else {
+      SetBackground(nullptr);
+    }
 
     SchedulePaint();
   }
 
   AppListViewDelegate* const view_delegate_;  // Not owned.
   bool selected_ = false;
   std::unique_ptr<SearchResult> search_result_;
 
   DISALLOW_COPY_AND_ASSIGN(SearchAnswerContainerView);
 };
@@ skipping 54 matching lines @@
 bool SearchResultAnswerCardView::OnKeyPressed(const ui::KeyEvent& event) {
   if (selected_index() == 0 &&
       search_answer_container_view_->OnKeyPressed(event)) {
     return true;
   }
 
   return SearchResultContainerView::OnKeyPressed(event);
 }
 
 }  // namespace app_list