Improve shelf widget delegate layout

The shelf widget delegate view, which also acts as a shelf widget's
contents view, contains two views - login shelf view, and the drag
handle.

Currently it uses fill layout manager for layout, which makes sense for
login shelf view, but not so much for the drag handle. To avoid drag
handle from getting resized to the whole shelf view bounds, the shelf
widget resets the delegate view layout manager when session state
changes. This works because login shelf and drag handle are mutually
exclusive. With new final first user run oobe screen mocks, which may
have swipe from shelf gesture enabled, login shelf may require drag
handle, which now break with fill layout manager.

This CL changes shelf widget delegate view to manage its own layout - it
sets the login shelf view to full shelf bounds, and centers the drag
handle within the shelf bounds. Also, it makes relationship between
delegate view and login shelf view more explicit, as the login view is
now added to delegate view using explicit AddLoginShelfView method,
instead of using GetContentsView()->AddChildView from shelf widget.

BUG=976949

Change-Id: Ic5a26c4ab657194c4cf4dfc5a4473eca4807146e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2071289
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744353}

ash/shelf/shelf_widget.cc

@@ -44,7 +44,6 @@
 #include "ui/gfx/skbitmap_operations.h"
 #include "ui/views/accessible_pane_view.h"
 #include "ui/views/focus/focus_search.h"
-#include "ui/views/layout/fill_layout.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/widget/widget_delegate.h"
 #include "ui/wm/core/coordinate_conversion.h"
@@ -119,6 +118,14 @@ class ShelfWidget::DelegateView : public views::WidgetDelegate,
 
   void SetParentLayer(ui::Layer* layer);
 
+  // Adds the login shelf view as a child of this view.
+  // Returns a pointer to the login shelf view passed in as an argument.
+  LoginShelfView* AddLoginShelfView(
+      std::unique_ptr<LoginShelfView> login_shelf_view) {
+    login_shelf_view_ = AddChildView(std::move(login_shelf_view));
+    return login_shelf_view_;
+  }
+
   void set_default_last_focusable_child(bool default_last_focusable_child) {
     default_last_focusable_child_ = default_last_focusable_child;
   }
@@ -147,6 +154,7 @@ class ShelfWidget::DelegateView : public views::WidgetDelegate,
 
   // views::AccessiblePaneView:
   views::View* GetDefaultFocusableChild() override;
+  void Layout() override;
 
   // ShelfBackgroundAnimatorObserver:
   void UpdateShelfBackground(SkColor color) override;
@@ -174,6 +182,11 @@ class ShelfWidget::DelegateView : public views::WidgetDelegate,
   bool hide_background_for_transitions_ = false;
   ShelfWidget* shelf_widget_;
   FocusCycler* focus_cycler_;
+
+  // Pointer to the login shelf view - visible only when the session is
+  // inactive. The view is owned by this view's hierarchy.
+  LoginShelfView* login_shelf_view_ = nullptr;
+
   // A background layer that may be visible depending on a
   // ShelfBackgroundAnimator.
   ui::LayerOwner opaque_background_;
@@ -211,7 +224,6 @@ ShelfWidget::DelegateView::DelegateView(ShelfWidget* shelf_widget)
   DCHECK(shelf_widget_);
   set_owned_by_client();  // Deleted by DeleteDelegate().
 
-  SetLayoutManager(std::make_unique<views::FillLayout>());
   set_allow_deactivate_on_esc(true);
 
   // |animating_background_| will be made visible during hotseat animations.
@@ -281,7 +293,7 @@ bool ShelfWidget::DelegateView::CanActivate() const {
   // This widget only contains anything interesting to activate in login/lock
   // screen mode. Only allow activation from the focus cycler, not from mouse
   // events, etc.
-  return shelf_widget_->login_shelf_view_->GetVisible() && focus_cycler_ &&
+  return login_shelf_view_->GetVisible() && focus_cycler_ &&
          focus_cycler_->widget_activating() == GetWidget();
 }
 
@@ -375,15 +387,8 @@ void ShelfWidget::DelegateView::UpdateDragHandle() {
     drag_handle_->SetVisible(false);
     return;
   }
-  drag_handle_->SetVisible(true);
 
-  const int x = (shelf_widget_->GetClientAreaBoundsInScreen().width() -
-                 kDragHandleSize.width()) /
-                2;
-  const int y =
-      (ShelfConfig::Get()->in_app_shelf_size() - kDragHandleSize.height()) / 2;
-  drag_handle_->SetBounds(x, y, kDragHandleSize.width(),
-                          kDragHandleSize.height());
+  drag_handle_->SetVisible(true);
 }
 
 void ShelfWidget::DelegateView::OnBoundsChanged(const gfx::Rect& old_bounds) {
@@ -407,8 +412,8 @@ views::View* ShelfWidget::DelegateView::GetDefaultFocusableChild() {
   if (!IsUsingViewsShelf())
     return GetFirstFocusableChild();
 
-  if (shelf_widget_->login_shelf_view_->GetVisible()) {
-    return FindFirstOrLastFocusableChild(shelf_widget_->login_shelf_view_,
+  if (login_shelf_view_->GetVisible()) {
+    return FindFirstOrLastFocusableChild(login_shelf_view_,
                                          default_last_focusable_child_);
   }
   // If the login shelf view is not visible, there is nothing else to focus
@@ -416,6 +421,14 @@ views::View* ShelfWidget::DelegateView::GetDefaultFocusableChild() {
   return nullptr;
 }
 
+void ShelfWidget::DelegateView::Layout() {
+  login_shelf_view_->SetBoundsRect(GetLocalBounds());
+
+  gfx::Rect drag_handle_bounds = GetLocalBounds();
+  drag_handle_bounds.ClampToCenteredSize(kDragHandleSize);
+  drag_handle_->SetBoundsRect(drag_handle_bounds);
+}
+
 void ShelfWidget::DelegateView::UpdateShelfBackground(SkColor color) {
   opaque_background()->SetColor(color);
   UpdateOpaqueBackground();
@@ -457,8 +470,8 @@ bool ShelfWidget::GetHitTestRects(aura::Window* target,
   // This should only get called when the login shelf is visible, i.e. not
   // during an active session. In an active session, hit test rects should be
   // calculated higher up in the class hierarchy by |EasyResizeWindowTargeter|.
-  // When in OOBE or locked/login screen, let events pass through empty parts
-  // of the shelf.
+  // When in OOBE or locked/login screen, let events pass through empty parts of
+  // the shelf.
   DCHECK(login_shelf_view_->GetVisible());
   gfx::Rect login_view_button_bounds =
       login_shelf_view_->ConvertRectToWidget(login_shelf_view_->GetMirroredRect(
@@ -528,8 +541,9 @@ void ShelfWidget::Initialize(aura::Window* shelf_container) {
   DCHECK(shelf_container);
 
   login_shelf_view_ =
-      new LoginShelfView(RootWindowController::ForWindow(shelf_container)
-                             ->lock_screen_action_background_controller());
+      delegate_view_->AddLoginShelfView(std::make_unique<LoginShelfView>(
+          RootWindowController::ForWindow(shelf_container)
+              ->lock_screen_action_background_controller()));
 
   views::Widget::InitParams params(
       views::Widget::InitParams::TYPE_WINDOW_FRAMELESS);
@@ -543,10 +557,8 @@ void ShelfWidget::Initialize(aura::Window* shelf_container) {
 
   // The shelf should not take focus when initially shown.
   set_focus_on_creation(false);
-  SetContentsView(delegate_view_);
   delegate_view_->SetParentLayer(GetLayer());
-
-  GetContentsView()->AddChildView(login_shelf_view_);
+  SetContentsView(delegate_view_);
 
   shelf_layout_manager_->AddObserver(this);
   shelf_container->SetLayoutManager(shelf_layout_manager_);
@@ -854,14 +866,7 @@ void ShelfWidget::OnSessionStateChanged(session_manager::SessionState state) {
     hotseat_transition_animator_->SetAnimationsEnabledInSessionState(
         show_hotseat);
     login_shelf_view()->SetVisible(!show_hotseat);
-    delegate_view_->SetLayoutManager(
-        show_hotseat ? nullptr : std::make_unique<views::FillLayout>());
-
-    // When FillLayout is no longer the layout manager, ensure the correct size
-    // for the drag handle is set.
-    if (show_hotseat)
-      delegate_view_->UpdateDragHandle();
-
+    delegate_view_->UpdateDragHandle();
     ShowIfHidden();
   }
   shelf_layout_manager_->SetDimmed(false);