views: fade buttons in inactive widgets

This change:
1) Adds an inner WidgetObserver subclass to Button to allow Button to observe
   its Widget's activation state changing;
2) Introduces a notion of "visual state" to buttons, as distinct from their
   existing state; the visual state governs how a button is drawn.
3) Has LabelButton use the visual state to decide which image to use instead
   of the raw state.

The end result is that when a LabelButton's Widget deactivates, that LabelButton
will take on a disabled appearance.

Bug: 848593
Change-Id: If5bd135c254fd36669e76fd39338dc24387602aa
Reviewed-on: https://chromium-review.googlesource.com/c/1251330
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600471}

ui/views/controls/button/button.cc

@@ -43,6 +43,30 @@ const int kHoverFadeDurationMs = 150;
 
 }  // namespace
 
+////////////////////////////////////////////////////////////////////////////////
+// WidgetObserverButtonBridge:
+Button::WidgetObserverButtonBridge::WidgetObserverButtonBridge(Button* button)
+    : owner_(button) {
+  DCHECK(button->GetWidget());
+  button->GetWidget()->AddObserver(this);
+}
+
+Button::WidgetObserverButtonBridge::~WidgetObserverButtonBridge() {
+  if (owner_)
+    owner_->GetWidget()->RemoveObserver(this);
+}
+
+void Button::WidgetObserverButtonBridge::OnWidgetActivationChanged(
+    Widget* widget,
+    bool active) {
+  owner_->WidgetActivationChanged(widget, active);
+}
+
+void Button::WidgetObserverButtonBridge::OnWidgetDestroying(Widget* widget) {
+  widget->RemoveObserver(this);
+  owner_ = nullptr;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Button, static public:
 
@@ -129,6 +153,14 @@ void Button::SetState(ButtonState state) {
   SchedulePaint();
 }
 
+Button::ButtonState Button::GetVisualState() const {
+  if (PlatformStyle::kInactiveWidgetControlsAppearDisabled && GetWidget() &&
+      !GetWidget()->IsActive()) {
+    return STATE_DISABLED;
+  }
+  return state();
+}
+
 void Button::StartThrobbing(int cycles_til_stop) {
   if (!animate_on_state_change_)
     return;
@@ -456,6 +488,15 @@ void Button::OnBlur() {
     SchedulePaint();
 }
 
+void Button::AddedToWidget() {
+  if (PlatformStyle::kInactiveWidgetControlsAppearDisabled)
+    widget_observer_ = std::make_unique<WidgetObserverButtonBridge>(this);
+}
+
+void Button::RemovedFromWidget() {
+  widget_observer_.reset();
+}
+
 std::unique_ptr<InkDrop> Button::CreateInkDrop() {
   std::unique_ptr<views::InkDropImpl> ink_drop = CreateDefaultInkDropImpl();
   ink_drop->SetShowHighlightOnFocus(!focus_ring_);
@@ -568,4 +609,8 @@ bool Button::ShouldEnterHoveredState() {
   return check_mouse_position && IsMouseHovered();
 }
 
+void Button::WidgetActivationChanged(Widget* widget, bool active) {
+  StateChanged(state());
+}
+
 }  // namespace views

ui/views/controls/button/button.h

@@ -15,6 +15,7 @@
 #include "ui/views/animation/ink_drop_state.h"
 #include "ui/views/controls/focus_ring.h"
 #include "ui/views/painter.h"
+#include "ui/views/widget/widget_observer.h"
 
 namespace views {
 
@@ -96,6 +97,9 @@ class VIEWS_EXPORT Button : public InkDropHostView,
   // like event dispatching, focus traversals, etc. Calling SetEnabled(false)
   // will also set the state of |this| to STATE_DISABLED.
   void SetState(ButtonState state);
+  // Returns the visual appearance state of the button. This takes into account
+  // both the button's display state and the state of the containing widget.
+  ButtonState GetVisualState() const;
 
   // Starts throbbing. See HoverAnimation for a description of cycles_til_stop.
   // This method does nothing if |animate_on_state_change_| is false.
@@ -183,6 +187,8 @@ class VIEWS_EXPORT Button : public InkDropHostView,
       const ViewHierarchyChangedDetails& details) override;
   void OnFocus() override;
   void OnBlur() override;
+  void AddedToWidget() override;
+  void RemovedFromWidget() override;
 
   // Overridden from InkDropHostView:
   std::unique_ptr<InkDrop> CreateInkDrop() override;
@@ -261,6 +267,28 @@ class VIEWS_EXPORT Button : public InkDropHostView,
  private:
   FRIEND_TEST_ALL_PREFIXES(BlueButtonTest, Border);
 
+  // Bridge class to allow Button to observe a Widget without being a
+  // WidgetObserver. This is desirable because many Button subclasses are
+  // themselves WidgetObservers, and if Button is a WidgetObserver, any change
+  // to its WidgetObserver overrides requires updating all the subclasses as
+  // well.
+  class WidgetObserverButtonBridge : public WidgetObserver {
+   public:
+    WidgetObserverButtonBridge(Button* owner);
+    ~WidgetObserverButtonBridge() override;
+
+    // WidgetObserver:
+    void OnWidgetActivationChanged(Widget* widget, bool active) override;
+    void OnWidgetDestroying(Widget* widget) override;
+
+   private:
+    Button* owner_;
+
+    DISALLOW_COPY_AND_ASSIGN(WidgetObserverButtonBridge);
+  };
+
+  void WidgetActivationChanged(Widget* widget, bool active);
+
   // The text shown in a tooltip.
   base::string16 tooltip_text_;
 
@@ -306,6 +334,8 @@ class VIEWS_EXPORT Button : public InkDropHostView,
 
   std::unique_ptr<Painter> focus_painter_;
 
+  std::unique_ptr<WidgetObserverButtonBridge> widget_observer_;
+
   DISALLOW_COPY_AND_ASSIGN(Button);
 };
 

ui/views/controls/button/label_button.cc

@@ -493,7 +493,7 @@ void LabelButton::UpdateStyleToIndicateDefaultStatus() {
 }
 
 void LabelButton::UpdateImage() {
-  image_->SetImage(GetImage(state()));
+  image_->SetImage(GetImage(GetVisualState()));
   ResetCachedPreferredSize();
 }
 

ui/views/style/platform_style.cc

@@ -63,6 +63,7 @@ const bool PlatformStyle::kTextfieldScrollsToStartOnFocusChange = false;
 const bool PlatformStyle::kTextfieldUsesDragCursorWhenDraggable = true;
 const bool PlatformStyle::kShouldElideBookmarksInBookmarksBar = false;
 const bool PlatformStyle::kPreferFocusRings = false;
+const bool PlatformStyle::kInactiveWidgetControlsAppearDisabled = false;
 
 // static
 std::unique_ptr<ScrollBar> PlatformStyle::CreateScrollBar(bool is_horizontal) {

ui/views/style/platform_style.h

@@ -83,6 +83,9 @@ class VIEWS_EXPORT PlatformStyle {
   // hover state on focus.
   static const bool kPreferFocusRings;
 
+  // Whether controls in inactive widgets appear disabled.
+  static const bool kInactiveWidgetControlsAppearDisabled;
+
   // Creates the default scrollbar for the given orientation.
   static std::unique_ptr<ScrollBar> CreateScrollBar(bool is_horizontal);
 

ui/views/style/platform_style_mac.mm

@@ -43,6 +43,7 @@ const bool PlatformStyle::kTreeViewSelectionPaintsEntireRow = true;
 const bool PlatformStyle::kShouldElideBookmarksInBookmarksBar = true;
 const bool PlatformStyle::kUseRipples = false;
 const bool PlatformStyle::kPreferFocusRings = true;
+const bool PlatformStyle::kInactiveWidgetControlsAppearDisabled = true;
 
 const Button::NotifyAction PlatformStyle::kMenuNotifyActivationAction =
     Button::NOTIFY_ON_PRESS;