[Shelf] Show navigation widget before setting the focus

The native view of the navigation widget is not activatable when its
target visibility is false. As a result, when the navigation widget
is hidden, it fails to get the focus through the FOCUS_SHELF
accelerator.

This CL fixes the issue by showing the navigation widget before setting
the focus.

Bug: 1111426
Change-Id: I9a1303ff6170eb98b255e6ce5d3814efce4d08c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2337097
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794746}

ash/shelf/shelf_focus_cycler.cc

@@ -65,7 +65,7 @@ void ShelfFocusCycler::FocusNavigation(bool last_element) {
     FocusOut(last_element, SourceView::kShelfNavigationView);
     return;
   }
-  navigation_widget->SetDefaultLastFocusableChild(last_element);
+  navigation_widget->PrepareForGettingFocus(last_element);
   Shell::Get()->focus_cycler()->FocusWidget(navigation_widget);
 }
 

ash/shelf/shelf_layout_manager_unittest.cc

@@ -577,6 +577,26 @@ TEST_P(ShelfLayoutManagerTest, VisibleWhenLockScreenShowing) {
             GetShelfWidget()->GetBackgroundType());
 }
 
+// Verifies that the hidden shelf shows after triggering the FOCUS_SHELF
+// accelerator (https://crbug.com/1111426).
+TEST_F(ShelfLayoutManagerTest, ShowHiddenShelfByFocusShelfAccelerator) {
+  // Open a window so that the shelf will auto-hide.
+  std::unique_ptr<aura::Window> window(CreateTestWindow());
+  window->Show();
+  Shelf* shelf = GetPrimaryShelf();
+  shelf->SetAutoHideBehavior(ShelfAutoHideBehavior::kAlways);
+  EXPECT_EQ(SHELF_AUTO_HIDE, shelf->GetVisibilityState());
+  EXPECT_EQ(SHELF_AUTO_HIDE_HIDDEN, shelf->GetAutoHideState());
+
+  // Focus on the shelf by accelerator.
+  Shell::Get()->accelerator_controller()->PerformActionIfEnabled(FOCUS_SHELF,
+                                                                 {});
+
+  // Shelf should be visible.
+  EXPECT_EQ(SHELF_AUTO_HIDE, shelf->GetVisibilityState());
+  EXPECT_EQ(SHELF_AUTO_HIDE_SHOWN, shelf->GetAutoHideState());
+}
+
 TEST_F(ShelfLayoutManagerTest, ShelfDoesNotAutoHideWithVoxAndTabletMode) {
   TabletModeControllerTestApi().EnterTabletMode();
   // Open a window so that the shelf will auto-hide.

ash/shelf/shelf_navigation_widget.cc

@@ -666,6 +666,21 @@ gfx::Rect ShelfNavigationWidget::GetVisibleBounds() const {
   return gfx::Rect(target_bounds_.origin(), clip_rect_.size());
 }
 
+void ShelfNavigationWidget::PrepareForGettingFocus(bool last_element) {
+  SetDefaultLastFocusableChild(last_element);
+
+  // The native view of the navigation widget is not activatable when its target
+  // visibility is false. So show the widget before setting focus.
+
+  // Layer opacity should be set first. Because it is not allowed that a window
+  // is visible but the layers alpha is fully transparent.
+  ui::Layer* layer = GetLayer();
+  if (layer->GetTargetOpacity() != 1.f)
+    GetLayer()->SetOpacity(1.f);
+  if (!IsVisible())
+    ShowInactive();
+}
+
 void ShelfNavigationWidget::HandleLocaleChange() {
   delegate_->home_button()->HandleLocaleChange();
   delegate_->back_button()->HandleLocaleChange();

ash/shelf/shelf_navigation_widget.h

@@ -84,6 +84,9 @@ class ASH_EXPORT ShelfNavigationWidget : public ShelfComponent,
   // Returns the visible part's bounds in screen coordinates.
   gfx::Rect GetVisibleBounds() const;
 
+  // Do preparations before setting focus on the navigation widget.
+  void PrepareForGettingFocus(bool last_element);
+
   // Called when shelf layout manager detects a locale change. Reloads the
   // home and back button tooltips and accessibility name strings.
   void HandleLocaleChange();