Implemented swipe to close in overview mode.

ash/wm/overview/transparent_activate_window_button.cc

Index: ash/wm/overview/transparent_activate_window_button.cc
diff --git a/ash/wm/overview/transparent_activate_window_button.cc b/ash/wm/overview/transparent_activate_window_button.cc
index 5c6a404f57521155f3e45a4cb4972b12df3c8524..ff0e4842a5a6da89b1f69f295798335ce6b7c866 100644
--- a/ash/wm/overview/transparent_activate_window_button.cc
+++ b/ash/wm/overview/transparent_activate_window_button.cc
@@ -6,9 +6,11 @@
 
 #include <vector>
 
+#include "ash/ash_switches.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/wm/overview/transparent_activate_window_button_delegate.h"
+#include "base/command_line.h"
 #include "ui/events/event.h"
 #include "ui/events/gesture_event_details.h"
 #include "ui/gfx/display.h"
@@ -22,6 +24,35 @@ namespace ash {
 namespace {
 const char kTransparentButtonName[] = "TransparentButton";
 
+// The default close window distance minimum.
+const int kDefaultCloseWindowDistanceMinimum = 100;
+
+// The minimum fling velocity which will cause a window to be closed.  Unit is
+// pixels per second.
+const float kMinimumFlingVelocity = 4000.0f;
+
+// Initializes the event handler transparent window.
+views::Widget* InitEventHandler(aura::Window* root_window) {
+  views::Widget* widget = new views::Widget;
+  views::Widget::InitParams params;
+  params.type = views::Widget::InitParams::TYPE_POPUP;
+  params.ownership = views::Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
+  params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
+  params.accept_events = true;
+  params.parent = Shell::GetContainer(root_window,
+                                      kShellWindowId_OverlayContainer);
+  widget->set_focus_on_creation(false);
+  widget->Init(params);
+  widget->Show();
+
+  aura::Window* handler = widget->GetNativeWindow();
+  handler->parent()->StackChildAtBottom(handler);
+
+  return widget;
+}
+
+}  // namespace
+
 // Transparent button that handles events to activate or close windows in
 // overview mode.
 class TransparentButton
@@ -34,6 +65,10 @@ class TransparentButton
 
   TransparentActivateWindowButtonDelegate* delegate() { return delegate_; }
 
+  void set_close_window_distance_minimum(int distance) {
+    close_window_distance_minimum_ = distance;
+  }
+
   // views::View:
   virtual void OnGestureEvent(ui::GestureEvent* event) override;
 
@@ -47,13 +82,32 @@ class TransparentButton
  private:
   TransparentActivateWindowButtonDelegate* delegate_;
 
+  // True if the swipe to close feature is disabled.
+  const bool swipe_to_close_disabled_;
+
+  // The original X location for a tap down event. |original_x_| is in the local
+  // coordinate space as |this|.
+  float original_x_;
+
+  // The velocity of the current fling gesture.  A fling is active iff
+  // |flint_velocity_x_| has a value greater than 0.
+  float fling_velocity_x_;
+
+  // The minimum distance, in pixels, for which a touch drag should cause a
+  // window to be closed.
+  int close_window_distance_minimum_;
+
   DISALLOW_COPY_AND_ASSIGN(TransparentButton);
 };
 
 TransparentButton::TransparentButton(
-        TransparentActivateWindowButtonDelegate* delegate)
-    : CustomButton(this),
-      delegate_(delegate) {
+    TransparentActivateWindowButtonDelegate* delegate)
+    : views::CustomButton(this),
+      delegate_(delegate),
+      swipe_to_close_disabled_(CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kAshDisableSwipeToCloseInOverviewMode)),
+      fling_velocity_x_(0.0f),
+      close_window_distance_minimum_(kDefaultCloseWindowDistanceMinimum) {
 }
 
 TransparentButton::~TransparentButton() {
@@ -74,6 +128,37 @@ void TransparentButton::OnGestureEvent(ui::GestureEvent* event) {
     GetWidget()->ReleaseCapture();
   }
 
+  if (swipe_to_close_disabled_) {
+    CustomButton::OnGestureEvent(event);
+    return;
+  }
+
+  int delta_x = event->x() - original_x_;
+
+  switch (event->type()) {
+    case ui::ET_GESTURE_TAP_DOWN:
+      original_x_ = event->x();
+      break;
+    case ui::ET_GESTURE_SCROLL_BEGIN:
+    case ui::ET_GESTURE_SCROLL_UPDATE:
+      delegate_->Scroll(delta_x);
+      break;
+    case ui::ET_SCROLL_FLING_START:
+      fling_velocity_x_ = fabs(event->details().velocity_x());
+      break;
+    case ui::ET_GESTURE_END:
+      if (abs(delta_x) > close_window_distance_minimum_ ||
+          fling_velocity_x_ > kMinimumFlingVelocity) {
+        delegate_->Close();
+      } else {
+        delegate_->CancelScroll();
+      }
+      original_x_ = 0;
+      fling_velocity_x_ = 0.0f;
+      break;
+    default:
+      break;
+  }
   CustomButton::OnGestureEvent(event);
   event->StopPropagation();
 }
@@ -83,28 +168,6 @@ void TransparentButton::ButtonPressed(views::Button* sender,
   delegate_->Select();
 }
 
-// Initializes the event handler transparent window.
-views::Widget* InitEventHandler(aura::Window* root_window) {
-  views::Widget* widget = new views::Widget;
-  views::Widget::InitParams params;
-  params.type = views::Widget::InitParams::TYPE_POPUP;
-  params.ownership = views::Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
-  params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
-  params.accept_events = true;
-  params.parent = Shell::GetContainer(root_window,
-                                      kShellWindowId_OverlayContainer);
-  widget->set_focus_on_creation(false);
-  widget->Init(params);
-  widget->Show();
-
-  aura::Window* handler = widget->GetNativeWindow();
-  handler->parent()->StackChildAtBottom(handler);
-
-  return widget;
-}
-
-}  // namespace
-
 TransparentActivateWindowButton::TransparentActivateWindowButton(
         aura::Window* root_window,
         TransparentActivateWindowButtonDelegate* delegate)
@@ -130,6 +193,11 @@ void TransparentActivateWindowButton::SetBounds(const gfx::Rect& bounds) {
   window->SetBoundsInScreen(bounds, display);
 }
 
+void TransparentActivateWindowButton::SetCloseWindowDistanceMinimum(
+    int distance) {
+  transparent_button_->set_close_window_distance_minimum(distance);
+}
+
 void TransparentActivateWindowButton::SendFocusAlert() const {
   event_handler_widget_->GetContentsView()->
       NotifyAccessibilityEvent(ui::AX_EVENT_FOCUS, true);