[ABANDONED] Simplify ash shelf dimmer.

ash/shelf/shelf_widget.cc

Index: ash/shelf/shelf_widget.cc
diff --git a/ash/shelf/shelf_widget.cc b/ash/shelf/shelf_widget.cc
index 0b986a38b947c47dc1f83a0c9218f75998244855..30773f212cd34aa830ab848f3bc165e8785cadb8 100644
--- a/ash/shelf/shelf_widget.cc
+++ b/ash/shelf/shelf_widget.cc
@@ -6,233 +6,50 @@
 
 #include "ash/aura/wm_shelf_aura.h"
 #include "ash/aura/wm_window_aura.h"
-#include "ash/common/ash_switches.h"
 #include "ash/common/focus_cycler.h"
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shelf/shelf_constants.h"
 #include "ash/common/shelf/shelf_delegate.h"
-#include "ash/common/shelf/shelf_model.h"
 #include "ash/common/shelf/wm_shelf_util.h"
-#include "ash/common/shell_window_ids.h"
 #include "ash/common/system/status_area_widget.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
+#include "ash/common/wm_lookup.h"
 #include "ash/common/wm_root_window_controller.h"
 #include "ash/common/wm_shell.h"
 #include "ash/shelf/shelf.h"
 #include "ash/shelf/shelf_layout_manager.h"
-#include "ash/shelf/shelf_util.h"
-#include "ash/shelf/shelf_view.h"
 #include "ash/shell.h"
 #include "ash/wm/status_area_layout_manager.h"
-#include "ash/wm/window_properties.h"
 #include "ash/wm/workspace_controller.h"
 #include "grit/ash_resources.h"
 #include "ui/aura/window.h"
-#include "ui/aura/window_event_dispatcher.h"
-#include "ui/aura/window_observer.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
-#include "ui/events/event_constants.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/image/image.h"
 #include "ui/gfx/image/image_skia_operations.h"
 #include "ui/gfx/skbitmap_operations.h"
 #include "ui/views/accessible_pane_view.h"
+#include "ui/events/event_handler.h"
 #include "ui/views/layout/fill_layout.h"
+#include "ui/views/pointer_watcher.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/widget/widget_delegate.h"
-#include "ui/wm/core/coordinate_conversion.h"
 #include "ui/wm/core/easy_resize_window_targeter.h"
-#include "ui/wm/public/activation_client.h"
 
 namespace ash {
 
 namespace {
 // Size of black border at bottom (or side) of shelf.
 const int kNumBlackPixels = 3;
-// Alpha to paint dimming image with.
-const int kDimAlpha = 128;
 
-// The time to dim and un-dim.
+// The time to dim and un-dim, and the opacities used for dimming.
 const int kTimeToDimMs = 3000;   // Slow in dimming.
 const int kTimeToUnDimMs = 200;  // Fast in activating.
-
-// Class used to slightly dim shelf items when maximized and visible.
-class DimmerView : public views::View,
-                   public views::WidgetDelegate,
-                   BackgroundAnimatorDelegate {
- public:
-  // If |disable_dimming_animations_for_test| is set, all alpha animations will
-  // be performed instantly.
-  DimmerView(ShelfWidget* shelf_widget,
-             bool disable_dimming_animations_for_test);
-  ~DimmerView() override;
-
-  // Called by |DimmerEventFilter| when the mouse |hovered| state changes.
-  void SetHovered(bool hovered);
-
-  // Force the dimmer to be undimmed.
-  void ForceUndimming(bool force);
-
-  // views::WidgetDelegate overrides:
-  views::Widget* GetWidget() override { return View::GetWidget(); }
-  const views::Widget* GetWidget() const override { return View::GetWidget(); }
-
-  // BackgroundAnimatorDelegate overrides:
-  void UpdateBackground(int alpha) override {
-    alpha_ = alpha;
-    SchedulePaint();
-  }
-
-  // views::View overrides:
-  void OnPaintBackground(gfx::Canvas* canvas) override;
-
-  // A function to test the current alpha used.
-  int get_dimming_alpha_for_test() { return alpha_; }
-
- private:
-  // This class monitors mouse events to see if it is on top of the shelf.
-  class DimmerEventFilter : public ui::EventHandler {
-   public:
-    explicit DimmerEventFilter(DimmerView* owner);
-    ~DimmerEventFilter() override;
-
-    // Overridden from ui::EventHandler:
-    void OnMouseEvent(ui::MouseEvent* event) override;
-    void OnTouchEvent(ui::TouchEvent* event) override;
-
-   private:
-    // The owning class.
-    DimmerView* owner_;
-
-    // TRUE if the mouse is inside the shelf.
-    bool mouse_inside_;
-
-    // TRUE if a touch event is inside the shelf.
-    bool touch_inside_;
-
-    DISALLOW_COPY_AND_ASSIGN(DimmerEventFilter);
-  };
-
-  // The owning shelf widget.
-  ShelfWidget* shelf_;
-
-  // The alpha to use for covering the shelf.
-  int alpha_;
-
-  // True if the event filter claims that we should not be dimmed.
-  bool is_hovered_;
-
-  // True if someone forces us not to be dimmed (e.g. a menu is open).
-  bool force_hovered_;
-
-  // True if animations should be suppressed for a test.
-  bool disable_dimming_animations_for_test_;
-
-  // The animator for the background transitions.
-  BackgroundAnimator background_animator_;
-
-  // Notification of entering / exiting of the shelf area by mouse.
-  std::unique_ptr<DimmerEventFilter> event_filter_;
-
-  DISALLOW_COPY_AND_ASSIGN(DimmerView);
-};
-
-DimmerView::DimmerView(ShelfWidget* shelf_widget,
-                       bool disable_dimming_animations_for_test)
-    : shelf_(shelf_widget),
-      alpha_(kDimAlpha),
-      is_hovered_(false),
-      force_hovered_(false),
-      disable_dimming_animations_for_test_(disable_dimming_animations_for_test),
-      background_animator_(this, 0, kDimAlpha) {
-  event_filter_.reset(new DimmerEventFilter(this));
-  // Make sure it is undimmed at the beginning and then fire off the dimming
-  // animation.
-  background_animator_.SetPaintsBackground(false, BACKGROUND_CHANGE_IMMEDIATE);
-  SetHovered(false);
-}
-
-DimmerView::~DimmerView() {}
-
-void DimmerView::SetHovered(bool hovered) {
-  // Remember the hovered state so that we can correct the state once a
-  // possible force state has disappeared.
-  is_hovered_ = hovered;
-  // Undimm also if we were forced to by e.g. an open menu.
-  hovered |= force_hovered_;
-  background_animator_.SetDuration(hovered ? kTimeToUnDimMs : kTimeToDimMs);
-  background_animator_.SetPaintsBackground(!hovered,
-                                           disable_dimming_animations_for_test_
-                                               ? BACKGROUND_CHANGE_IMMEDIATE
-                                               : BACKGROUND_CHANGE_ANIMATE);
-}
-
-void DimmerView::ForceUndimming(bool force) {
-  bool previous = force_hovered_;
-  force_hovered_ = force;
-  // If the forced change does change the result we apply the change.
-  if (is_hovered_ || force_hovered_ != is_hovered_ || previous)
-    SetHovered(is_hovered_);
-}
-
-void DimmerView::OnPaintBackground(gfx::Canvas* canvas) {
-  SkPaint paint;
-  ui::ResourceBundle* rb = &ui::ResourceBundle::GetSharedInstance();
-  gfx::ImageSkia shelf_background =
-      *rb->GetImageNamed(IDR_ASH_SHELF_DIMMING).ToImageSkia();
-
-  if (!IsHorizontalAlignment(shelf_->GetAlignment())) {
-    shelf_background = gfx::ImageSkiaOperations::CreateRotatedImage(
-        shelf_background, shelf_->GetAlignment() == SHELF_ALIGNMENT_LEFT
-                              ? SkBitmapOperations::ROTATION_90_CW
-                              : SkBitmapOperations::ROTATION_270_CW);
-  }
-  paint.setAlpha(alpha_);
-  canvas->DrawImageInt(shelf_background, 0, 0, shelf_background.width(),
-                       shelf_background.height(), 0, 0, width(), height(),
-                       false, paint);
-}
-
-DimmerView::DimmerEventFilter::DimmerEventFilter(DimmerView* owner)
-    : owner_(owner), mouse_inside_(false), touch_inside_(false) {
-  Shell::GetInstance()->AddPreTargetHandler(this);
-}
-
-DimmerView::DimmerEventFilter::~DimmerEventFilter() {
-  Shell::GetInstance()->RemovePreTargetHandler(this);
-}
-
-void DimmerView::DimmerEventFilter::OnMouseEvent(ui::MouseEvent* event) {
-  if (event->type() != ui::ET_MOUSE_MOVED &&
-      event->type() != ui::ET_MOUSE_DRAGGED)
-    return;
-
-  gfx::Point screen_point(event->location());
-  ::wm::ConvertPointToScreen(static_cast<aura::Window*>(event->target()),
-                             &screen_point);
-  bool inside = owner_->GetBoundsInScreen().Contains(screen_point);
-  if (mouse_inside_ || touch_inside_ != inside || touch_inside_)
-    owner_->SetHovered(inside || touch_inside_);
-  mouse_inside_ = inside;
-}
-
-void DimmerView::DimmerEventFilter::OnTouchEvent(ui::TouchEvent* event) {
-  bool touch_inside = false;
-  if (event->type() != ui::ET_TOUCH_RELEASED &&
-      event->type() != ui::ET_TOUCH_CANCELLED) {
-    gfx::Point screen_point(event->location());
-    ::wm::ConvertPointToScreen(static_cast<aura::Window*>(event->target()),
-                               &screen_point);
-    touch_inside = owner_->GetBoundsInScreen().Contains(screen_point);
-  }
-
-  if (mouse_inside_ || touch_inside_ != mouse_inside_ || touch_inside)
-    owner_->SetHovered(mouse_inside_ || touch_inside);
-  touch_inside_ = touch_inside;
-}
+const float kDimOpactiy = 0.25f;
+const float kUnDimOpactiy = 0.0f;
 
 // ShelfWindowTargeter makes it easier to resize windows with the mouse when the
 // window-edge slightly overlaps with the shelf edge. The targeter also makes it
@@ -292,29 +109,82 @@ class ShelfWindowTargeter : public ::wm::EasyResizeWindowTargeter,
   DISALLOW_COPY_AND_ASSIGN(ShelfWindowTargeter);
 };
 
+class ShelfDimmer : public ui::EventHandler, public views::PointerWatcher {
+ public:
+  explicit ShelfDimmer(ShelfWidget* shelf) : shelf_widget_(shelf) {
+    // TODO(msw): Need to do the same for the status area widget...
+    WmWindow* window = WmLookup::Get()->GetWindowForWidget(shelf_widget_);
+    window->AddLimitedPreTargetHandler(this);
+    window = WmLookup::Get()->GetWindowForWidget(shelf_widget_->status_area_widget());
+    window->AddLimitedPreTargetHandler(this);
+    WmShell::Get()->AddPointerWatcher(this);
+  }
+
+  ~ShelfDimmer() override {
+    // TODO(msw): Remove the pre-target handler(s)...
+    WmWindow* window = WmLookup::Get()->GetWindowForWidget(shelf_widget_);
+    window->RemoveLimitedPreTargetHandler(this);
+    window = WmLookup::Get()->GetWindowForWidget(shelf_widget_->status_area_widget());
+    window->RemoveLimitedPreTargetHandler(this);
+    WmShell::Get()->RemovePointerWatcher(this);
+  }
+
+  // ui::EventHandler:
+  void OnMouseEvent(ui::MouseEvent* event) override {
+    LOG(ERROR) << "MSW ShelfDimmer OnMouseEvent " << event->name();
+    shelf_widget_->SetDimsShelf(
+        event->type() == ui::ET_MOUSE_EXITED ||
+        (event->type() == ui::ET_MOUSE_RELEASED &&
+         !shelf_widget_->GetRootView()->bounds().Contains(event->location())));
+  }
+  void OnTouchEvent(ui::TouchEvent* event) override {
+    LOG(ERROR) << "MSW ShelfDimmer OnTouchEvent " << event->name();
+    if (event->type() != ui::ET_TOUCH_PRESSED)
+      shelf_widget_->SetDimsShelf(event->type() != ui::ET_TOUCH_MOVED);
+  }
+
+  // views::PointerWatcher:
+  void OnMousePressed(const ui::MouseEvent& event,
+                      const gfx::Point& location_in_screen,
+                      views::Widget* target) override {}
+  void OnTouchPressed(const ui::TouchEvent& event,
+                      const gfx::Point& location_in_screen,
+                      views::Widget* target) override {
+    LOG(ERROR) << "MSW ShelfDimmer::OnTouchPressed " << event.name();
+    shelf_widget_->SetDimsShelf(
+        !shelf_widget_->GetWindowBoundsInScreen().Contains(location_in_screen));
+  }
+
+ private:
+  ShelfWidget* shelf_widget_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShelfDimmer);
+};
+
 }  // namespace
 
 // The contents view of the Shelf. This view contains ShelfView and
 // sizes it to the width of the shelf minus the size of the status area.
 class ShelfWidget::DelegateView : public views::WidgetDelegate,
                                   public views::AccessiblePaneView,
-                                  public BackgroundAnimatorDelegate,
-                                  public aura::WindowObserver {
+                                  public BackgroundAnimatorDelegate {
  public:
   explicit DelegateView(ShelfWidget* shelf);
   ~DelegateView() override;
 
-  void set_focus_cycler(FocusCycler* focus_cycler) {
-    focus_cycler_ = focus_cycler;
-  }
+  void set_focus_cycler(FocusCycler* cycler) { focus_cycler_ = cycler; }
   FocusCycler* focus_cycler() { return focus_cycler_; }
 
   ui::Layer* opaque_background() { return &opaque_background_; }
   ui::Layer* opaque_foreground() { return &opaque_foreground_; }
 
-  // Set if the shelf area is dimmed (eg when a window is maximized).
+  // Set if the shelf is dimmed (eg. when a window is maximized).
   void SetDimmed(bool dimmed);
-  bool GetDimmed() const;
+
+  // Used to initialize or shutdown the dimmer.
+  void set_dimmer(std::unique_ptr<ShelfDimmer> dimmer) {
+    shelf_dimmer_ = std::move(dimmer);
+  }
 
   void SetParentLayer(ui::Layer* layer);
 
@@ -330,64 +200,36 @@ class ShelfWidget::DelegateView : public views::WidgetDelegate,
   // This will be called when the parent local bounds change.
   void OnBoundsChanged(const gfx::Rect& old_bounds) override;
 
-  // aura::WindowObserver overrides:
-  // This will be called when the shelf itself changes its absolute position.
-  // Since the |dimmer_| panel needs to be placed in screen coordinates it needs
-  // to be repositioned. The difference to the OnBoundsChanged call above is
-  // that this gets also triggered when the shelf only moves.
-  void OnWindowBoundsChanged(aura::Window* window,
-                             const gfx::Rect& old_bounds,
-                             const gfx::Rect& new_bounds) override;
-
   // BackgroundAnimatorDelegate overrides:
   void UpdateBackground(int alpha) override;
 
   // Force the shelf to be presented in an undimmed state.
   void ForceUndimming(bool force);
 
-  // A function to test the current alpha used by the dimming bar. If there is
-  // no dimmer active, the function will return -1.
-  int GetDimmingAlphaForTest();
-
-  // A function to test the bounds of the dimming bar. Returns gfx::Rect() if
-  // the dimmer is inactive.
-  gfx::Rect GetDimmerBoundsForTest();
-
-  // Disable dimming animations for running tests. This needs to be called
-  // prior to the creation of of the |dimmer_|.
-  void disable_dimming_animations_for_test() {
-    disable_dimming_animations_for_test_ = true;
-  }
+  // Set the shelf dimming |opacity| over the |animation_time_ms| duration.
+  void SetShelfDimming(float opacity, int animation_time_ms);
 
  private:
   ShelfWidget* shelf_;
-  std::unique_ptr<views::Widget> dimmer_;
-  FocusCycler* focus_cycler_;
-  int alpha_;
-  // A black background layer which is shown when a maximized window is visible.
+  FocusCycler* focus_cycler_ = nullptr;
+  int alpha_ = 0;
+  // A black background shown when a maximized window is visible.
   ui::Layer opaque_background_;
-  // A black foreground layer which is shown while transitioning between users.
-  // Note: Since the back- and foreground layers have different functions they
-  // can be used simultaneously - so no repurposing possible.
+  // A black foreground shown during user transitions; also used to dim shelf
+  // items when a maximized window is visible and the shelf is not hovered.
   ui::Layer opaque_foreground_;
 
-  // The view which does the dimming.
-  DimmerView* dimmer_view_;
-
-  // True if dimming animations should be turned off.
-  bool disable_dimming_animations_for_test_;
+  std::unique_ptr<ShelfDimmer> shelf_dimmer_;
+  bool force_dimmer_off_ = false;
+  float stored_dimmer_opacity_ = 0.0f;
 
   DISALLOW_COPY_AND_ASSIGN(DelegateView);
 };
 
 ShelfWidget::DelegateView::DelegateView(ShelfWidget* shelf)
     : shelf_(shelf),
-      focus_cycler_(NULL),
-      alpha_(0),
       opaque_background_(ui::LAYER_SOLID_COLOR),
-      opaque_foreground_(ui::LAYER_SOLID_COLOR),
-      dimmer_view_(NULL),
-      disable_dimming_animations_for_test_(false) {
+      opaque_foreground_(ui::LAYER_SOLID_COLOR) {
   SetLayoutManager(new views::FillLayout());
   set_allow_deactivate_on_esc(true);
   opaque_background_.SetColor(SK_ColorBLACK);
@@ -398,45 +240,15 @@ ShelfWidget::DelegateView::DelegateView(ShelfWidget* shelf)
   opaque_foreground_.SetOpacity(0.0f);
 }
 
-ShelfWidget::DelegateView::~DelegateView() {
-  // Make sure that the dimmer goes away since it might have set an observer.
-  SetDimmed(false);
-}
-
-void ShelfWidget::DelegateView::SetDimmed(bool value) {
-  if (value == (dimmer_.get() != NULL))
-    return;
-
-  if (value) {
-    dimmer_.reset(new views::Widget);
-    views::Widget::InitParams params(
-        views::Widget::InitParams::TYPE_WINDOW_FRAMELESS);
-    params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
-    params.activatable = views::Widget::InitParams::ACTIVATABLE_NO;
-    params.accept_events = false;
-    params.ownership = views::Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
-    params.parent = shelf_->GetNativeView();
-    dimmer_->Init(params);
-    dimmer_->GetNativeWindow()->SetName("ShelfDimmer");
-    dimmer_->SetBounds(shelf_->GetWindowBoundsInScreen());
-    // The shelf should not take focus when it is initially shown.
-    dimmer_->set_focus_on_creation(false);
-    dimmer_view_ = new DimmerView(shelf_, disable_dimming_animations_for_test_);
-    dimmer_->SetContentsView(dimmer_view_);
-    dimmer_->GetNativeView()->SetName("ShelfDimmerView");
-    dimmer_->Show();
-    shelf_->GetNativeView()->AddObserver(this);
-  } else {
-    // Some unit tests will come here with a destroyed window.
-    if (shelf_->GetNativeView())
-      shelf_->GetNativeView()->RemoveObserver(this);
-    dimmer_view_ = NULL;
-    dimmer_.reset(NULL);
-  }
-}
+ShelfWidget::DelegateView::~DelegateView() {}
 
-bool ShelfWidget::DelegateView::GetDimmed() const {
-  return dimmer_.get() && dimmer_->IsVisible();
+void ShelfWidget::DelegateView::SetDimmed(bool dimmed) {
+  if (force_dimmer_off_)
+    stored_dimmer_opacity_ = dimmed ? kDimOpactiy : kUnDimOpactiy;
+  else if (dimmed)
+    SetShelfDimming(kDimOpactiy, kTimeToDimMs);
+  else
+    SetShelfDimming(kUnDimOpactiy, kTimeToUnDimMs);
 }
 
 void ShelfWidget::DelegateView::SetParentLayer(ui::Layer* layer) {
@@ -524,40 +336,34 @@ void ShelfWidget::DelegateView::ReorderChildLayers(ui::Layer* parent_layer) {
 void ShelfWidget::DelegateView::OnBoundsChanged(const gfx::Rect& old_bounds) {
   opaque_background_.SetBounds(GetLocalBounds());
   opaque_foreground_.SetBounds(GetLocalBounds());
-  if (dimmer_)
-    dimmer_->SetBounds(GetBoundsInScreen());
 }
 
-void ShelfWidget::DelegateView::OnWindowBoundsChanged(
-    aura::Window* window,
-    const gfx::Rect& old_bounds,
-    const gfx::Rect& new_bounds) {
-  // Coming here the shelf got repositioned and since the |dimmer_| is placed
-  // in screen coordinates and not relative to the parent it needs to be
-  // repositioned accordingly.
-  dimmer_->SetBounds(GetBoundsInScreen());
+void ShelfWidget::DelegateView::UpdateBackground(int alpha) {
+  alpha_ = alpha;
+  SchedulePaint();
 }
 
 void ShelfWidget::DelegateView::ForceUndimming(bool force) {
-  if (GetDimmed())
-    dimmer_view_->ForceUndimming(force);
+  force_dimmer_off_ = force;
+  if (force)
+    stored_dimmer_opacity_ = opaque_foreground_.opacity();
+  opaque_foreground_.SetOpacity(force ? kUnDimOpactiy : stored_dimmer_opacity_);
 }
 
-int ShelfWidget::DelegateView::GetDimmingAlphaForTest() {
-  if (GetDimmed())
-    return dimmer_view_->get_dimming_alpha_for_test();
-  return -1;
-}
+void ShelfWidget::DelegateView::SetShelfDimming(float opacity,
+                                                int animation_time_ms) {
+  if (opaque_foreground_.GetTargetOpacity() == opacity)
+    return;
 
-gfx::Rect ShelfWidget::DelegateView::GetDimmerBoundsForTest() {
-  if (GetDimmed())
-    return dimmer_view_->GetBoundsInScreen();
-  return gfx::Rect();
-}
+  std::unique_ptr<ui::ScopedLayerAnimationSettings> opaque_foreground_animation;
+  opaque_foreground_animation.reset(
+      new ui::ScopedLayerAnimationSettings(opaque_foreground_.GetAnimator()));
+  opaque_foreground_animation->SetTransitionDuration(
+      base::TimeDelta::FromMilliseconds(animation_time_ms));
+  opaque_foreground_animation->SetPreemptionStrategy(
+      ui::LayerAnimator::IMMEDIATELY_ANIMATE_TO_NEW_TARGET);
 
-void ShelfWidget::DelegateView::UpdateBackground(int alpha) {
-  alpha_ = alpha;
-  SchedulePaint();
+  opaque_foreground_.SetOpacity(opacity);
 }
 
 ShelfWidget::ShelfWidget(WmWindow* wm_shelf_container,
@@ -611,6 +417,8 @@ ShelfWidget::ShelfWidget(WmWindow* wm_shelf_container,
   status_container->SetEventTargeter(std::unique_ptr<ui::EventTargeter>(
       new ShelfWindowTargeter(status_container, shelf_layout_manager_)));
 
+  delegate_view_->set_dimmer(base::MakeUnique<ShelfDimmer>(this));
+
   views::Widget::AddObserver(this);
 }
 
@@ -642,6 +450,10 @@ void ShelfWidget::SetPaintsBackground(
   // See also DockedBackgroundWidget::SetPaintsBackground.
   background_animator_.SetPaintsBackground(
       background_type != SHELF_BACKGROUND_DEFAULT, change_type);
+
+  // Start or stop dimming as appropriate.
+  LOG(ERROR) << "MSW SetPaintsBackground this:" << this << " max:" << (background_type == SHELF_BACKGROUND_MAXIMIZED);
+  SetDimsShelf(background_type == SHELF_BACKGROUND_MAXIMIZED);
 }
 
 ShelfBackgroundType ShelfWidget::GetBackgroundType() const {
@@ -654,24 +466,11 @@ ShelfBackgroundType ShelfWidget::GetBackgroundType() const {
 }
 
 void ShelfWidget::HideShelfBehindBlackBar(bool hide, int animation_time_ms) {
-  if (IsShelfHiddenBehindBlackBar() == hide)
-    return;
-
-  ui::Layer* opaque_foreground = delegate_view_->opaque_foreground();
-  float target_opacity = hide ? 1.0f : 0.0f;
-  std::unique_ptr<ui::ScopedLayerAnimationSettings> opaque_foreground_animation;
-  opaque_foreground_animation.reset(
-      new ui::ScopedLayerAnimationSettings(opaque_foreground->GetAnimator()));
-  opaque_foreground_animation->SetTransitionDuration(
-      base::TimeDelta::FromMilliseconds(animation_time_ms));
-  opaque_foreground_animation->SetPreemptionStrategy(
-      ui::LayerAnimator::REPLACE_QUEUED_ANIMATIONS);
-
-  opaque_foreground->SetOpacity(target_opacity);
+  delegate_view_->SetShelfDimming(hide ? 1.0f : 0.0f, animation_time_ms);
 }
 
 bool ShelfWidget::IsShelfHiddenBehindBlackBar() const {
-  return delegate_view_->opaque_foreground()->GetTargetOpacity() != 0.0f;
+  return delegate_view_->opaque_foreground()->GetTargetOpacity() == 1.0f;
 }
 
 // static
@@ -712,6 +511,15 @@ void ShelfWidget::OnShelfAlignmentChanged() {
 }
 
 void ShelfWidget::SetDimsShelf(bool dimming) {
+  LOG(ERROR) << "MSW SetDimsShelf A " << dimming;
+  // The shelf can only be dimmed when shown and the background is maximized.
+  dimming &= (GetBackgroundType() == SHELF_BACKGROUND_MAXIMIZED && shelf_ &&
+              shelf_->auto_hide_behavior() == SHELF_AUTO_HIDE_BEHAVIOR_NEVER);
+
+  // Dimming is not possible nor useful when hidden behind a black bar.
+  if (IsShelfHiddenBehindBlackBar() || GetDimsShelf() == dimming)
+    return;
+
   delegate_view_->SetDimmed(dimming);
   // Repaint all children, allowing updates to reflect dimmed state eg:
   // status area background, app list button and overflow button.
@@ -721,7 +529,7 @@ void ShelfWidget::SetDimsShelf(bool dimming) {
 }
 
 bool ShelfWidget::GetDimsShelf() const {
-  return delegate_view_->GetDimmed();
+  return delegate_view_->opaque_foreground()->GetTargetOpacity() == kDimOpactiy;
 }
 
 void ShelfWidget::CreateShelf(WmShelfAura* wm_shelf_aura) {
@@ -764,6 +572,8 @@ FocusCycler* ShelfWidget::GetFocusCycler() {
 }
 
 void ShelfWidget::Shutdown() {
+  delegate_view_->set_dimmer(nullptr);
+
   // Shutting down the status area widget may cause some widgets (e.g. bubbles)
   // to close, so uninstall the ShelfLayoutManager event filters first. Don't
   // reset the pointer until later because other widgets (e.g. app list) may
@@ -791,26 +601,19 @@ void ShelfWidget::OnWidgetActivationChanged(views::Widget* widget,
     delegate_view_->GetFocusManager()->ClearFocus();
 }
 
-int ShelfWidget::GetDimmingAlphaForTest() {
-  if (delegate_view_)
-    return delegate_view_->GetDimmingAlphaForTest();
-  return -1;
-}
-
-gfx::Rect ShelfWidget::GetDimmerBoundsForTest() {
-  if (delegate_view_)
-    return delegate_view_->GetDimmerBoundsForTest();
-  return gfx::Rect();
+void ShelfWidget::WillDeleteShelfLayoutManager() {
+  shelf_layout_manager_->RemoveObserver(this);
+  shelf_layout_manager_ = NULL;
 }
 
-void ShelfWidget::DisableDimmingAnimationsForTest() {
-  DCHECK(delegate_view_);
-  return delegate_view_->disable_dimming_animations_for_test();
+void ShelfWidget::OnDragEnter() {
+  LOG(ERROR) << "MSW ShelfWidget::OnDragEnter";
+  SetDimsShelf(false);
 }
 
-void ShelfWidget::WillDeleteShelfLayoutManager() {
-  shelf_layout_manager_->RemoveObserver(this);
-  shelf_layout_manager_ = NULL;
+void ShelfWidget::OnDragExit() {
+  LOG(ERROR) << "MSW ShelfWidget::OnDragExit";
+  SetDimsShelf(true);
 }
 
 void ShelfWidget::OnMouseEvent(ui::MouseEvent* event) {