Moves to the last page again in case that the selected page is lost.

BUG=133260
TEST=app_list_unittest passed


Review URL: https://chromiumcodereview.appspot.com/10571002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@143161 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 28 insertions, 7 deletions

diff --git a/ui/app_list/apps_grid_view.cc b/ui/app_list/apps_grid_view.cc
index e57389a..38bbda4 100644
--- a/ui/app_list/apps_grid_view.cc
+++ b/ui/app_list/apps_grid_view.cc
@@ -290,8 +290,6 @@ void AppsGridView::Update() {
 void AppsGridView::UpdatePaginationModel() {
   pagination_model_->SetTotalPages(
       (child_count() - 1) / tiles_per_page() + 1);
-  if (pagination_model_->selected_page() < 0)
-    pagination_model_->SelectPage(0, false /* animate */);
 }
 
 AppListItemView* AppsGridView::CreateViewForItemAtIndex(size_t index) {
diff --git a/ui/app_list/pagination_model.cc b/ui/app_list/pagination_model.cc
index 6fa19b6..d58a5fc 100644
--- a/ui/app_list/pagination_model.cc
+++ b/ui/app_list/pagination_model.cc
@@ -27,6 +27,10 @@ void PaginationModel::SetTotalPages(int total_pages) {
     return;
 
   total_pages_ = total_pages;
+  if (selected_page_ < 0)
+    SelectPage(0, false /* animate */);
+  if (selected_page_ >= total_pages_)
+    SelectPage(total_pages_ - 1, false /* animate */);
   FOR_EACH_OBSERVER(PaginationModelObserver,
                     observers_,
                     TotalPagesChanged());
diff --git a/ui/app_list/pagination_model_unittest.cc b/ui/app_list/pagination_model_unittest.cc
index ed6a480..2a6624d 100644
--- a/ui/app_list/pagination_model_unittest.cc
+++ b/ui/app_list/pagination_model_unittest.cc
@@ -138,7 +138,6 @@ class PaginationModelTest : public testing::Test {
 };
 
 TEST_F(PaginationModelTest, SelectPage) {
-  pagination_.SelectPage(0, false /* animate */);
   pagination_.SelectPage(2, false /* animate */);
   pagination_.SelectPage(4, false /* animate */);
   pagination_.SelectPage(3, false /* animate */);
@@ -146,13 +145,13 @@ TEST_F(PaginationModelTest, SelectPage) {
 
   EXPECT_EQ(0, observer_.transition_start_count());
   EXPECT_EQ(0, observer_.transition_end_count());
-  EXPECT_EQ(5, observer_.selection_count());
-  EXPECT_EQ(std::string("0 2 4 3 1"), observer_.selected_pages());
+  EXPECT_EQ(4, observer_.selection_count());
+  EXPECT_EQ(std::string("2 4 3 1"), observer_.selected_pages());
 
   // Nothing happens if select the same page.
   pagination_.SelectPage(1, false /* animate */);
-  EXPECT_EQ(5, observer_.selection_count());
-  EXPECT_EQ(std::string("0 2 4 3 1"), observer_.selected_pages());
+  EXPECT_EQ(4, observer_.selection_count());
+  EXPECT_EQ(std::string("2 4 3 1"), observer_.selected_pages());
 }
 
 TEST_F(PaginationModelTest, SelectPageAnimated) {
@@ -369,5 +368,25 @@ TEST_F(PaginationModelTest, LongScroll) {
   EXPECT_EQ(1, observer_.selection_count());
 }
 
+TEST_F(PaginationModelTest, SelectedPageIsLost) {
+  pagination_.SetTotalPages(2);
+  // The selected page is set to 0 once the total number of pages are set.
+  EXPECT_EQ(0, pagination_.selected_page());
+
+  pagination_.SelectPage(1, false /* animate */);
+  EXPECT_EQ(1, pagination_.selected_page());
+
+  // The selected page is unchanged if it's still valid.
+  pagination_.SetTotalPages(3);
+  EXPECT_EQ(1, pagination_.selected_page());
+  pagination_.SetTotalPages(2);
+  EXPECT_EQ(1, pagination_.selected_page());
+
+  // But if the currently selected_page exceeds the total number of pages,
+  // it automatically switches to the last page.
+  pagination_.SetTotalPages(1);
+  EXPECT_EQ(0, pagination_.selected_page());
+}
+
 }  // namespace test
 }  // namespace app_list