Corner Passthrough for Accessibility

ui/chromeos/touch_exploration_controller.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/chromeos/touch_exploration_controller.h"
 
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/events/event.h"
 #include "ui/events/event_processor.h"
 #include "ui/events/event_utils.h"
 #include "ui/gfx/geometry/rect.h"
 
 #define VLOG_STATE() if (VLOG_IS_ON(0)) VlogState(__func__)
 #define VLOG_EVENT(event) if (VLOG_IS_ON(0)) VlogEvent(event, __func__)
 
 namespace ui {
 
 namespace {
 
 // Delay between adjustment sounds.
 const base::TimeDelta kSoundDelay = base::TimeDelta::FromMilliseconds(150);
 
+// Delay before corner passthrough activates.
+const base::TimeDelta kCornerPassthroughDelay =
+    base::TimeDelta::FromMilliseconds(700);
+
 // In ChromeOS, VKEY_LWIN is synonymous for the search key.
 const ui::KeyboardCode kChromeOSSearchKey = ui::VKEY_LWIN;
 }  // namespace
 
 TouchExplorationController::TouchExplorationController(
     aura::Window* root_window,
     TouchExplorationControllerDelegate* delegate)
     : root_window_(root_window),
       delegate_(delegate),
       state_(NO_FINGERS_DOWN),
       gesture_provider_(this),
       prev_state_(NO_FINGERS_DOWN),
       VLOG_on_(true),
-      tick_clock_(NULL) {
+      tick_clock_(NULL),
+      waiting_for_corner_passthrough_(false) {
   CHECK(root_window);
   root_window->GetHost()->GetEventSource()->AddEventRewriter(this);
 }
 
 TouchExplorationController::~TouchExplorationController() {
   root_window_->GetHost()->GetEventSource()->RemoveEventRewriter(this);
 }
 
 ui::EventRewriteStatus TouchExplorationController::RewriteEvent(
     const ui::Event& event,
     scoped_ptr<ui::Event>* rewritten_event) {
   if (!event.IsTouchEvent()) {
     return ui::EVENT_REWRITE_CONTINUE;
   }
   const ui::TouchEvent& touch_event = static_cast<const ui::TouchEvent&>(event);
 
   // If the tap timer should have fired by now but hasn't, run it now and
   // stop the timer. This is important so that behavior is consistent with
   // the timestamps of the events, and not dependent on the granularity of
   // the timer.
   if (tap_timer_.IsRunning() &&
       touch_event.time_stamp() - initial_press_->time_stamp() >
           gesture_detector_config_.double_tap_timeout) {
     tap_timer_.Stop();
     OnTapTimerFired();
     // Note: this may change the state. We should now continue and process
     // this event under this new state.
   }
 
+  if (long_press_timer_.IsRunning() &&
+      event.time_stamp() - initial_press_->time_stamp() >
+          gesture_detector_config_.longpress_timeout) {
+    long_press_timer_.Stop();
+    OnLongPressTimerFired();
+  }
+
   const ui::EventType type = touch_event.type();
   const gfx::PointF& location = touch_event.location_f();
   const int touch_id = touch_event.touch_id();
 
   // Always update touch ids and touch locations, so we can use those
   // no matter what state we're in.
   if (type == ui::ET_TOUCH_PRESSED) {
+    // If the user enters the screen from the edge then send an earcon.
+    gfx::Point edges = touch_event.location();
+    if (FindEdgesWithinBounds(edges, kLeavingScreenEdge) != NO_EDGE)

[aboxhall, 2014/08/06 18:10:45]

Do we want to not play this if a user already has a finger down? I'm wondering
whether this logic belongs in InNoFingersDown instead.

[lisayin, 2014/08/06 20:37:35]

Hmmm. Good point. I'll move it to InNoFingersDown.

+      delegate_->PlayEnterScreenEarcon();
     current_touch_ids_.push_back(touch_id);
     touch_locations_.insert(std::pair<int, gfx::PointF>(touch_id, location));
   } else if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
     // In order to avoid accidentally double tapping when moving off the edge of
     // the screen, the state will be rewritten to NoFingersDown.
     TouchEvent touch_event = static_cast<const TouchEvent&>(event);
-    if (FindEdgesWithinBounds(touch_event.location(), kLeavingScreenEdge) !=
-        NO_EDGE) {
-      if (current_touch_ids_.size() == 0) {
-        ResetToNoFingersDown();
-      }
+    gfx::Point edges = touch_event.location();
+    if (FindEdgesWithinBounds(edges, kLeavingScreenEdge) != NO_EDGE) {

[aboxhall, 2014/08/06 18:10:45]

Perhaps this needs to check for state as well: I imagine there are several
states for which it doesn't make sense (e.g. mid-swipe gesture? Do we want
someone to know they swiped off the screen if a swipe has already been
successfully registered?)

[lisayin, 2014/08/06 20:37:35]

I actually think it makes sense to notify the user that their swipe has left the
screen since it'll still process the gesture even if they've left the screen.
Swiping off the screen in the middle of a gesture will cause it to process since
we're only checking the type of the event and not where it's located.

On 2014/08/06 18:10:45, aboxhall wrote:

[aboxhall, 2014/08/06 21:03:12]

I guess it could be handy knowing that you'll consistently hear a beep if you
swipe off the edge, but I could imagine that if you're simply performing a swipe
gesture you don't care whether you've swiped off the edge: chances are you'll
lift your finger very shortly afterwards anyway (or else swipe off the screen
altogether) so it'll just be noise. Is that not the case?

[lisayin, 2014/08/06 21:48:22]

So another thing that kind of keeps the sound from playing is the fact that it
only plays if you're within a very small number of pixels. I played around with
gestures on the pixel and even when I leave the screen, the official "release"
location is actually a lot farther away from the edge. Should I compensate for
this discrepancy?

On 2014/08/06 21:03:12, aboxhall wrote:

+        // Indicates to the user that they are leaving the screen.
+      if (VLOG_on_)
+        VLOG(0) << "Leaving the Screen";
+      delegate_->PlayExitScreenEarcon();
+      if (current_touch_ids_.size() == 0)
+          ResetToNoFingersDown();
     }
 
     std::vector<int>::iterator it = std::find(
         current_touch_ids_.begin(), current_touch_ids_.end(), touch_id);
 
     // Can happen if touch exploration is enabled while fingers were down.
     if (it == current_touch_ids_.end())
       return ui::EVENT_REWRITE_CONTINUE;
 
     current_touch_ids_.erase(it);
@@ skipping 22 matching lines @@
     case DOUBLE_TAP_PENDING:
       return InDoubleTapPending(touch_event, rewritten_event);
     case TOUCH_RELEASE_PENDING:
       return InTouchReleasePending(touch_event, rewritten_event);
     case TOUCH_EXPLORATION:
       return InTouchExploration(touch_event, rewritten_event);
     case GESTURE_IN_PROGRESS:
       return InGestureInProgress(touch_event, rewritten_event);
     case TOUCH_EXPLORE_SECOND_PRESS:
       return InTouchExploreSecondPress(touch_event, rewritten_event);
+    case CORNER_PASSTHROUGH:
+      return InCornerPassthrough(touch_event, rewritten_event);
     case SLIDE_GESTURE:
       return InSlideGesture(touch_event, rewritten_event);
     case ONE_FINGER_PASSTHROUGH:
       return InOneFingerPassthrough(touch_event, rewritten_event);
     case WAIT_FOR_ONE_FINGER:
       return InWaitForOneFinger(touch_event, rewritten_event);
   }
   NOTREACHED();
   return ui::EVENT_REWRITE_CONTINUE;
 }
 
 ui::EventRewriteStatus TouchExplorationController::NextDispatchEvent(
     const ui::Event& last_event, scoped_ptr<ui::Event>* new_event) {
   NOTREACHED();
   return ui::EVENT_REWRITE_CONTINUE;
 }
 
 ui::EventRewriteStatus TouchExplorationController::InNoFingersDown(
     const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event) {
   const ui::EventType type = event.type();
-  if (type == ui::ET_TOUCH_PRESSED) {
-    initial_press_.reset(new TouchEvent(event));
-    last_unused_finger_event_.reset(new TouchEvent(event));
-    StartTapTimer();
-    gesture_provider_.OnTouchEvent(event);
-    gesture_provider_.OnTouchEventAck(false);
-    ProcessGestureEvents();
-    state_ = SINGLE_TAP_PRESSED;
-    VLOG_STATE();
-    return ui::EVENT_REWRITE_DISCARD;
+  if (type != ui::ET_TOUCH_PRESSED) {
+    NOTREACHED() << "Unexpected event type received: " << event.name();
+    return ui::EVENT_REWRITE_CONTINUE;
   }
-  NOTREACHED() << "Unexpected event type received: " << event.name();
-  return ui::EVENT_REWRITE_CONTINUE;
+  int location = FindEdgesWithinBounds(event.location(), kSlopDistanceFromEdge);
+  base::TimeDelta timeout;
+
+  // If the press was at a corner, the user might go into corner passthrough
+  // instead.
+  bool in_a_bottom_corner =
+      (BOTTOM_LEFT_CORNER == location) || (BOTTOM_RIGHT_CORNER == location);
+  if (in_a_bottom_corner) {
+    long_press_timer_.Start(FROM_HERE,
+                            gesture_detector_config_.longpress_timeout,
+                            this,
+                            &TouchExplorationController::OnLongPressTimerFired);
+    waiting_for_corner_passthrough_ = true;

[aboxhall, 2014/08/06 18:10:45]

Why not just use the long_press_timer_ (or corner_passthrough_timer_) to track
whether we're waiting for corner passthrough? When does it make sense to set
waiting_for_corner_passthrough_ to false but not stop the timer?

[lisayin, 2014/08/06 20:37:35]

I'm hoping to use this timer for evy's passthrough implementation as well so
that they both will fire an earcon if activated, but I have removed
waiting_for_corner_passthrough_ and renamed the timer to passthrough_timer_. 

+  } else {
+    waiting_for_corner_passthrough_ = false;
+  }
+  tap_timer_.Start(FROM_HERE,
+                   gesture_detector_config_.double_tap_timeout,
+                   this,
+                   &TouchExplorationController::OnTapTimerFired);
+  initial_press_.reset(new TouchEvent(event));
+  last_unused_finger_event_.reset(new TouchEvent(event));
+  gesture_provider_.OnTouchEvent(event);
+  gesture_provider_.OnTouchEventAck(false);
+  ProcessGestureEvents();
+  state_ = SINGLE_TAP_PRESSED;
+  VLOG_STATE();
+  return ui::EVENT_REWRITE_DISCARD;
 }
 
 ui::EventRewriteStatus TouchExplorationController::InSingleTapPressed(
     const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event) {
   const ui::EventType type = event.type();
 
+  int location = FindEdgesWithinBounds(event.location(), kMaxDistanceFromEdge);
+  bool in_a_bottom_corner =
+      (location == BOTTOM_LEFT_CORNER) || (location == BOTTOM_RIGHT_CORNER);
+  // If the event is from the initial press and the location is no longer in the
+  // corner, then we are not waiting for a corner passthrough anymore.
+  if (event.touch_id() == initial_press_->touch_id() && !in_a_bottom_corner) {
+    waiting_for_corner_passthrough_ = false;
+    if (long_press_timer_.IsRunning()) {

[aboxhall, 2014/08/06 18:10:44]

If we're not going to use this for anything other than corner passthrough,
perhaps it would be better named 'corner_passthrough_timer_'.

[lisayin, 2014/08/06 20:37:35]

Done.

+      long_press_timer_.Stop();
+      if (event.time_stamp() - initial_press_->time_stamp() >
+          gesture_detector_config_.double_tap_timeout) {
+        OnTapTimerFired();

[aboxhall, 2014/08/06 18:10:44]

Why do this? Could you add a comment?

[lisayin, 2014/08/06 20:37:35]

This is in case the finger moves out of the corner before the long press timer
has fired but after the tap timer has fired to make sure you can still go into
touch exploration.

[aboxhall, 2014/08/06 21:03:12]

Ah, I see now. But won't the tap timer have been running (due to line 190) and
caused OnTapTimerFired() to be executed already?

[lisayin, 2014/08/06 21:48:22]

In TapTimerFired, if the long press timer is running, I don't change the state.
So now that the long press timer has been stopped, I need to check to see if the
tap timer should have been fired or not.

On 2014/08/06 21:03:12, aboxhall wrote:

[aboxhall, 2014/08/06 22:01:24]

Oh, duh! Makes sense, thanks for the explanation :)

+      }
+    }
+  }
+
   if (type == ui::ET_TOUCH_PRESSED) {
     // TODO (evy, lisayin) : add support for multifinger swipes.
     // For now, we wait for there to be only one finger down again.
     state_ = WAIT_FOR_ONE_FINGER;
     return EVENT_REWRITE_DISCARD;
   } else if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
     if (current_touch_ids_.size() == 0 &&
         event.touch_id() == initial_press_->touch_id()) {
       state_ = SINGLE_TAP_RELEASED;
       VLOG_STATE();
@@ skipping 13 matching lines @@
         (event.time_stamp() - initial_press_->time_stamp()).InSecondsF();
     float velocity = distance / delta_time;
     if (VLOG_on_) {
       VLOG(0) << "\n Delta time: " << delta_time << "\n Distance: " << distance
               << "\n Velocity of click: " << velocity
               << "\n Minimum swipe velocity: "
               << gesture_detector_config_.minimum_swipe_velocity;
     }
     // Change to slide gesture if the slide occurred at the right edge.
     int edge = FindEdgesWithinBounds(event.location(), kMaxDistanceFromEdge);
-    if (edge & RIGHT_EDGE) {
+    if (edge & RIGHT_EDGE && edge != BOTTOM_RIGHT_CORNER) {
       state_ = SLIDE_GESTURE;
       VLOG_STATE();
       return InSlideGesture(event, rewritten_event);
     }
 
     // If the user moves fast enough from the initial touch location, start
     // gesture detection. Otherwise, jump to the touch exploration mode early.
     if (velocity > gesture_detector_config_.minimum_swipe_velocity) {
       state_ = GESTURE_IN_PROGRESS;
       VLOG_STATE();
@@ skipping 172 matching lines @@
     gesture_provider_.OnTouchEvent(event);
     gesture_provider_.OnTouchEventAck(false);
     if (current_touch_ids_.size() == 0) {
       ResetToNoFingersDown();
     }
   }
   ProcessGestureEvents();
   return ui::EVENT_REWRITE_DISCARD;
 }
 
+ui::EventRewriteStatus TouchExplorationController::InCornerPassthrough(
+    const ui::TouchEvent& event,
+    scoped_ptr<ui::Event>* rewritten_event) {
+  ui::EventType type = event.type();
+
+  // If the first finger has left the corner, then exit passthrough.
+  if (event.touch_id() == initial_press_->touch_id()) {
+    int edges = FindEdgesWithinBounds(event.location(), kSlopDistanceFromEdge);
+    bool in_a_bottom_corner = (edges == BOTTOM_LEFT_CORNER) ||
+                              (edges == BOTTOM_RIGHT_CORNER);
+    if (type == ui::ET_TOUCH_MOVED && in_a_bottom_corner)
+      return ui::EVENT_REWRITE_DISCARD;
+
+    if (current_touch_ids_.size() == 0) {
+      ResetToNoFingersDown();
+      return ui::EVENT_REWRITE_DISCARD;
+    }
+
+    waiting_for_corner_passthrough_ = false;
+    state_ = WAIT_FOR_ONE_FINGER;
+    VLOG_STATE();
+    return ui::EVENT_REWRITE_DISCARD;
+  }
+
+  rewritten_event->reset(new ui::TouchEvent(
+      type, event.location(), event.touch_id(), event.time_stamp()));
+  (*rewritten_event)->set_flags(event.flags());
+
+  if (current_touch_ids_.size() == 0)
+    ResetToNoFingersDown();
+
+  return ui::EVENT_REWRITE_REWRITTEN;
+}
+
 ui::EventRewriteStatus TouchExplorationController::InOneFingerPassthrough(
     const ui::TouchEvent& event,
     scoped_ptr<ui::Event>* rewritten_event) {
   ui::EventType type = event.type();
 
   if (!(type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED ||
         type == ui::ET_TOUCH_MOVED || type == ui::ET_TOUCH_PRESSED)) {
     NOTREACHED() << "Unexpected event type received: " << event.name();
     return ui::EVENT_REWRITE_CONTINUE;
   }
@@ skipping 55 matching lines @@
     VLOG_STATE();
     return ui::EVENT_REWRITE_REWRITTEN;
   }
   NOTREACHED() << "Unexpected event type received: " << event.name();
   return ui::EVENT_REWRITE_CONTINUE;
 }
 
 ui::EventRewriteStatus TouchExplorationController::InWaitForOneFinger(
     const ui::TouchEvent& event,
     scoped_ptr<ui::Event>* rewritten_event) {
+  waiting_for_corner_passthrough_ = false;
   ui::EventType type = event.type();
   if (!(type == ui::ET_TOUCH_PRESSED || type == ui::ET_TOUCH_MOVED ||
         type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED)) {
     NOTREACHED() << "Unexpected event type received: " << event.name();
     return ui::EVENT_REWRITE_CONTINUE;
   }
   if (current_touch_ids_.size() == 1) {
     EnterTouchToMouseMode();
     state_ = TOUCH_EXPLORATION;
     VLOG_STATE();
     *rewritten_event = CreateMouseMoveEvent(event.location(), event.flags());
     last_touch_exploration_.reset(new TouchEvent(event));
     return ui::EVENT_REWRITE_REWRITTEN;
   }
   return EVENT_REWRITE_DISCARD;
 }
 
 void TouchExplorationController::PlaySoundForTimer() {
-  delegate_->PlayVolumeAdjustSound();
+  delegate_->PlayVolumeAdjustEarcon();
 }
 
 ui::EventRewriteStatus TouchExplorationController::InSlideGesture(
     const ui::TouchEvent& event,
     scoped_ptr<ui::Event>* rewritten_event) {
   // The timer should not fire when sliding.
   if (tap_timer_.IsRunning())
     tap_timer_.Stop();
 
   ui::EventType type = event.type();
@@ skipping 19 matching lines @@
     return EVENT_REWRITE_DISCARD;
   }
 
   // This can occur if the user leaves the screen edge and then returns to it to
   // continue adjusting the sound.
   if (!sound_timer_.IsRunning()) {
     sound_timer_.Start(FROM_HERE,
                        kSoundDelay,
                        this,
                        &ui::TouchExplorationController::PlaySoundForTimer);
-    delegate_->PlayVolumeAdjustSound();
+    delegate_->PlayVolumeAdjustEarcon();
   }
 
   // There should not be more than one finger down.
   DCHECK(current_touch_ids_.size() <= 1);
   if (type == ui::ET_TOUCH_MOVED) {
     gesture_provider_.OnTouchEvent(event);
     gesture_provider_.OnTouchEventAck(false);
   }
   if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
     gesture_provider_.OnTouchEvent(event);
@@ skipping 42 matching lines @@
                             last_touch_exploration_->location();
       scoped_ptr<ui::TouchEvent> passthrough_press(
           new ui::TouchEvent(ui::ET_TOUCH_PRESSED,
                              last_touch_exploration_->location(),
                              last_unused_finger_event_->touch_id(),
                              Now()));
       DispatchEvent(passthrough_press.get());
       return;
     }
     case SINGLE_TAP_PRESSED:
+      if (waiting_for_corner_passthrough_)
+        return;
     case GESTURE_IN_PROGRESS:
       // Discard any pending gestures.
       delete gesture_provider_.GetAndResetPendingGestures();
       state_ = TOUCH_EXPLORATION;
       VLOG_STATE();
       break;
     default:
       return;
   }
   EnterTouchToMouseMode();
   scoped_ptr<ui::Event> mouse_move =
       CreateMouseMoveEvent(initial_press_->location(), initial_press_->flags());
   DispatchEvent(mouse_move.get());
   last_touch_exploration_.reset(new TouchEvent(*initial_press_));
 }
 
+void TouchExplorationController::OnLongPressTimerFired() {
+  if (waiting_for_corner_passthrough_) {

[aboxhall, 2014/08/06 18:10:44]

Invert this logic:
if (!waiting_for_corner_passthrough_)
  return;
...

[lisayin, 2014/08/06 20:37:35]

Done.

+    if (sound_timer_.IsRunning())
+      sound_timer_.Stop();
+    delegate_->PlayPassthroughEarcon();
+    delete gesture_provider_.GetAndResetPendingGestures();
+    state_ = CORNER_PASSTHROUGH;
+    VLOG_STATE();
+    return;
+  }
+}
+
 void TouchExplorationController::DispatchEvent(ui::Event* event) {
   ui::EventDispatchDetails result ALLOW_UNUSED =
       root_window_->GetHost()->dispatcher()->OnEventFromSource(event);
 }
 
 void TouchExplorationController::OnGestureEvent(
     ui::GestureEvent* gesture) {
   CHECK(gesture->IsGestureEvent());
   ui::EventType type = gesture->type();
   if (VLOG_on_)
@@ skipping 21 matching lines @@
     }
   }
 }
 
 void TouchExplorationController::SideSlideControl(ui::GestureEvent* gesture) {
   ui::EventType type = gesture->type();
   if (!gesture->IsScrollGestureEvent())
     return;
 
   if (type == ET_GESTURE_SCROLL_BEGIN) {
-    delegate_->PlayVolumeAdjustSound();
+    delegate_->PlayVolumeAdjustEarcon();
   }
 
   if (type == ET_GESTURE_SCROLL_END) {
     if (sound_timer_.IsRunning())
       sound_timer_.Stop();
-    delegate_->PlayVolumeAdjustSound();
+    delegate_->PlayVolumeAdjustEarcon();
   }
 
   // If the user is in the corner of the right side of the screen, the volume
   // will be automatically set to 100% or muted depending on which corner they
   // are in. Otherwise, the user will be able to adjust the volume by sliding
   // their finger along the right side of the screen. Volume is relative to
   // where they are on the right side of the screen.
   gfx::Point location = gesture->location();
   int edge = FindEdgesWithinBounds(location, kSlopDistanceFromEdge);
   if (!(edge & RIGHT_EDGE))
@@ skipping 126 matching lines @@
 void TouchExplorationController::EnterTouchToMouseMode() {
   aura::client::CursorClient* cursor_client =
       aura::client::GetCursorClient(root_window_);
   if (cursor_client && !cursor_client->IsMouseEventsEnabled())
     cursor_client->EnableMouseEvents();
   if (cursor_client && cursor_client->IsCursorVisible())
     cursor_client->HideCursor();
 }
 
 void TouchExplorationController::ResetToNoFingersDown() {
+  waiting_for_corner_passthrough_ = false;
   ProcessGestureEvents();
   if (sound_timer_.IsRunning())
     sound_timer_.Stop();
   state_ = NO_FINGERS_DOWN;
   VLOG_STATE();
   if (tap_timer_.IsRunning())
     tap_timer_.Stop();
 }
 
 void TouchExplorationController::VlogState(const char* function_name) {
@@ skipping 50 matching lines @@
     case DOUBLE_TAP_PENDING:
       return "DOUBLE_TAP_PENDING";
     case TOUCH_RELEASE_PENDING:
       return "TOUCH_RELEASE_PENDING";
     case TOUCH_EXPLORATION:
       return "TOUCH_EXPLORATION";
     case GESTURE_IN_PROGRESS:
       return "GESTURE_IN_PROGRESS";
     case TOUCH_EXPLORE_SECOND_PRESS:
       return "TOUCH_EXPLORE_SECOND_PRESS";
+    case CORNER_PASSTHROUGH:
+      return "CORNER_PASSTHROUGH";
     case SLIDE_GESTURE:
       return "SLIDE_GESTURE";
     case ONE_FINGER_PASSTHROUGH:
       return "ONE_FINGER_PASSTHROUGH";
     case WAIT_FOR_ONE_FINGER:
       return "WAIT_FOR_ONE_FINGER";
   }
   return "Not a state";
 }
 
 }  // namespace ui