Swipe Gestures for Accessibility

ui/chromeos/touch_exploration_controller.cc

Index: ui/chromeos/touch_exploration_controller.cc
diff --git a/ui/chromeos/touch_exploration_controller.cc b/ui/chromeos/touch_exploration_controller.cc
index 9763cae225c242b277a510f9ac92789e9ef8c75d..850e157441590b6d78f935de84f93cca73998693 100644
--- a/ui/chromeos/touch_exploration_controller.cc
+++ b/ui/chromeos/touch_exploration_controller.cc
@@ -31,6 +31,9 @@ const int kTouchIdUnassigned = 0;
 // initial_touch_id_passthrough_mapping_ a touch id anymore,
 // until all fingers are released.
 const int kTouchIdNone = -1;
+
+// In ChromeOS, VKEY_LWIN is synonymous for the search key.
+const ui::KeyboardCode kChromeOSSearchKey = ui::VKEY_LWIN;
 }  // namespace
 
 TouchExplorationController::TouchExplorationController(
@@ -39,6 +42,7 @@ TouchExplorationController::TouchExplorationController(
       initial_touch_id_passthrough_mapping_(kTouchIdUnassigned),
       state_(NO_FINGERS_DOWN),
       event_handler_for_testing_(NULL),
+      gesture_provider_(this),
       prev_state_(NO_FINGERS_DOWN) {
   CHECK(root_window);
   root_window->GetHost()->GetEventSource()->AddEventRewriter(this);
@@ -63,6 +67,10 @@ bool TouchExplorationController::IsInNoFingersDownStateForTesting() const {
   return state_ == NO_FINGERS_DOWN;
 }
 
+bool TouchExplorationController::IsInGestureInProgressStateForTesting() const {
+  return state_ == GESTURE_IN_PROGRESS;
+}
+
 ui::EventRewriteStatus TouchExplorationController::RewriteEvent(
     const ui::Event& event,
     scoped_ptr<ui::Event>* rewritten_event) {
@@ -128,6 +136,8 @@ ui::EventRewriteStatus TouchExplorationController::RewriteEvent(
       return InDoubleTapPressed(touch_event, rewritten_event);
     case TOUCH_EXPLORATION:
       return InTouchExploration(touch_event, rewritten_event);
+    case GESTURE_IN_PROGRESS:
+      return InGestureInProgress(touch_event, rewritten_event);
     case PASSTHROUGH_MINUS_ONE:
       return InPassthroughMinusOne(touch_event, rewritten_event);
     case TOUCH_EXPLORE_SECOND_PRESS:
@@ -153,6 +163,8 @@ ui::EventRewriteStatus TouchExplorationController::InNoFingersDown(
                      gesture_detector_config_.double_tap_timeout,
                      this,
                      &TouchExplorationController::OnTapTimerFired);
+    gesture_provider_.OnTouchEvent(event);
+    gesture_provider_.OnTouchEventAck(false);
     state_ = SINGLE_TAP_PRESSED;
     VLOG_STATE();
     return ui::EVENT_REWRITE_DISCARD;
@@ -178,17 +190,31 @@ ui::EventRewriteStatus TouchExplorationController::InSingleTapPressed(
     VLOG_STATE();
     return EVENT_REWRITE_DISCARD;
   } else if (type == ui::ET_TOUCH_MOVED) {
-    // If the user moves far enough from the initial touch location (outside
-    // the "slop" region, jump to the touch exploration mode early.
-    // TODO(evy, lisayin): Add gesture recognition here instead -
-    // we should probably jump to gesture mode here if the velocity is
-    // high enough, and touch exploration if the velocity is lower.
-    float delta = (event.location() - initial_press_->location()).Length();
-    if (delta > gesture_detector_config_.touch_slop) {
-      EnterTouchToMouseMode();
-      state_ = TOUCH_EXPLORATION;
-      VLOG_STATE();
-      return InTouchExploration(event, rewritten_event);
+    float delta_time =
+        (event.time_stamp() - initial_press_->time_stamp()).InSecondsF();
+    float delta_distance =
+        (event.location() - initial_press_->location()).Length();
+    float velocity = delta_distance / delta_time;
+    VLOG(0) << "\n Delta time: " << delta_time
+            << "\n Delta distance: " << delta_distance
+            << "\n Velocity of click: " << velocity
+            << "\n Minimum swipe velocity: "
+            << gesture_detector_config_.minimum_swipe_velocity;
+    if (delta_distance > gesture_detector_config_.touch_slop) {

[tdresser, 2014/06/25 14:48:40]

Invert this condition to reduce nesting.

if (delta_distance <= gesture_detector_config_.touch_slop)
  return EVENT_REWRITE_DISCARD;

[lisayin, 2014/06/25 22:51:05]

Done.

+      // If the user moves fast enough and far enough
+      // from the initial touch location, start gesture detection

[dmazzoni, 2014/06/25 05:06:02]

Nit: end sentence with period.

[lisayin, 2014/06/25 22:51:04]

Done.

+      // Otherwise, if the user moves far enough from the initial touch location
+      // outside the "slop" region, jump to the touch exploration mode early.
+      if (velocity > gesture_detector_config_.minimum_swipe_velocity) {
+        state_ = GESTURE_IN_PROGRESS;
+        VLOG_STATE();
+        return InGestureInProgress(event, rewritten_event);
+      } else {

[tdresser, 2014/06/25 14:48:40]

This "else" is unnecessary.

[lisayin, 2014/06/25 22:51:05]

Done.

+        EnterTouchToMouseMode();
+        state_ = TOUCH_EXPLORATION;
+        VLOG_STATE();
+        return InTouchExploration(event, rewritten_event);
+      }
     }
 
     return EVENT_REWRITE_DISCARD;
@@ -292,6 +318,26 @@ ui::EventRewriteStatus TouchExplorationController::InTouchExploration(
   return ui::EVENT_REWRITE_REWRITTEN;
 }
 
+ui::EventRewriteStatus TouchExplorationController::InGestureInProgress(
+    const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event) {
+  ui::EventType type = event.type();
+  if (type == ui::ET_TOUCH_PRESSED ||
+      event.touch_id() != initial_press_->touch_id()) {
+    return ui::EVENT_REWRITE_DISCARD;
+  }
+  if (type == ui::ET_TOUCH_MOVED) {
+    gesture_provider_.OnTouchEvent(event);
+    gesture_provider_.OnTouchEventAck(false);
+   }

[tdresser, 2014/06/25 14:48:40]

Indentation.

[lisayin, 2014/06/25 22:51:05]

Done.

+  if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
+    gesture_provider_.OnTouchEvent(event);
+    gesture_provider_.OnTouchEventAck(true);

[dmazzoni, 2014/06/25 05:06:02]

Are you sure you want to pass true here and false above?

[tdresser, 2014/06/25 14:48:40]

I'm fairly certain this should be "false".

[lisayin, 2014/06/25 22:51:05]

Done.

+    if (current_touch_ids_.size() == 0)
+      ResetToNoFingersDown();
+  }
+  return ui::EVENT_REWRITE_DISCARD;
+}
+
 ui::EventRewriteStatus TouchExplorationController::InPassthroughMinusOne(
     const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event) {
   ui::EventType type = event.type();
@@ -375,6 +421,7 @@ ui::EventRewriteStatus TouchExplorationController::InTouchExploreSecondPress(
                            initial_press_->touch_id(),
                            event.time_stamp()));
     (*rewritten_event)->set_flags(event.flags());
+    EnterTouchToMouseMode();
     state_ = TOUCH_EXPLORATION;
     VLOG_STATE();
     return ui::EVENT_REWRITE_REWRITTEN;
@@ -393,7 +440,10 @@ void TouchExplorationController::OnTapTimerFired() {
       last_touch_exploration_.reset(new TouchEvent(*initial_press_));
       return;
     case SINGLE_TAP_PRESSED:
+    case GESTURE_IN_PROGRESS:
       EnterTouchToMouseMode();
+      // Discard any pending gestures.
+      delete gesture_provider_.GetAndResetPendingGestures();
       state_ = TOUCH_EXPLORATION;
       VLOG_STATE();
       break;
@@ -417,6 +467,64 @@ void TouchExplorationController::DispatchEvent(ui::Event* event) {
       root_window_->GetHost()->dispatcher()->OnEventFromSource(event);
 }
 
+void TouchExplorationController::OnGestureEvent(ui::GestureEvent* gesture) {
+  CHECK(gesture->IsGestureEvent());
+  VLOG(0) << " \n Gesture Triggered: " << gesture->name();
+  if (tap_timer_.IsRunning())
+    tap_timer_.Stop();
+  switch (gesture->type()) {

[tdresser, 2014/06/25 14:48:40]

Unless you're likely to support other gestures, it would be simpler to just:

if (gesture->type() == ET_GESTURE_SWIPE) {
  OnSwipeEvent(gesture);
  return;
}
if (current_touch_ids_.size()) {
  ...

[lisayin, 2014/06/25 22:51:04]

Done.

+    case ET_GESTURE_SWIPE:
+      OnSwipeEvent(gesture);
+      return;
+    default:
+      if (current_touch_ids_.size() != 0) {

[tdresser, 2014/06/25 14:48:40]

From the style guide: "if one part of an if-else statement uses curly braces,
the other part must too:".

[lisayin, 2014/06/25 22:51:05]

Done.

+        EnterTouchToMouseMode();
+        state_ = TOUCH_EXPLORATION;
+      } else
+        ResetToNoFingersDown();
+      break;
+  }
+}
+
+void TouchExplorationController::OnSwipeEvent(ui::GestureEvent* swipe_gesture) {
+  // A swipe gesture contains details for the direction in which the swipe
+  // occurred.
+  GestureEventDetails event_details = swipe_gesture->details();
+  if (event_details.swipe_left()) {
+    DispatchShiftSearchKeyEvent(ui::VKEY_LEFT);
+    return;
+  } else if (event_details.swipe_right()) {
+    DispatchShiftSearchKeyEvent(ui::VKEY_RIGHT);
+    return;
+  } else if (event_details.swipe_up()) {
+    DispatchShiftSearchKeyEvent(ui::VKEY_UP);
+    return;
+  } else if (event_details.swipe_down()) {
+    DispatchShiftSearchKeyEvent(ui::VKEY_DOWN);
+    return;
+  }
+}
+
+void TouchExplorationController::DispatchShiftSearchKeyEvent(
+    const ui::KeyboardCode direction) {
+  // In order to activate the shortcut shift+search+<arrow key>
+  // three KeyPressed events must be dispatched in succession along
+  // with three KeyReleased events.
+  DispatchEvent(new ui::KeyEvent(
+      ui::ET_KEY_PRESSED, ui::VKEY_SHIFT, ui::EF_SHIFT_DOWN, false));
+  DispatchEvent(new ui::KeyEvent(
+      ui::ET_KEY_PRESSED, kChromeOSSearchKey, ui::EF_SHIFT_DOWN, false));
+  DispatchEvent(new ui::KeyEvent(
+      ui::ET_KEY_PRESSED, direction, ui::EF_SHIFT_DOWN, false));
+
+  DispatchEvent(new ui::KeyEvent(
+      ui::ET_KEY_RELEASED, direction, ui::EF_SHIFT_DOWN, false));
+  DispatchEvent(new ui::KeyEvent(
+      ui::ET_KEY_RELEASED, kChromeOSSearchKey, ui::EF_SHIFT_DOWN, false));
+  DispatchEvent(new ui::KeyEvent(
+      ui::ET_KEY_RELEASED, ui::VKEY_SHIFT, ui::EF_NONE, false));
+}
+
 scoped_ptr<ui::Event> TouchExplorationController::CreateMouseMoveEvent(
     const gfx::PointF& location,
     int flags) {
@@ -439,6 +547,15 @@ void TouchExplorationController::EnterTouchToMouseMode() {
 }
 
 void TouchExplorationController::ResetToNoFingersDown() {
+  scoped_ptr<ScopedVector<ui::GestureEvent> > gestures;
+  gestures.reset(gesture_provider_.GetAndResetPendingGestures());
+  if (gestures != NULL) {
+    for (ScopedVector<GestureEvent>::iterator i = gestures->begin();
+         i != gestures->end();
+         ++i) {
+      OnGestureEvent(*i);

[tdresser, 2014/06/25 14:48:40]

Just making sure - there's no way that OnGestureEvent could cause an
aura::Window to be destroyed, is there?

[dmazzoni, 2014/06/25 15:39:44]

As of this change, no - but in the future you should be able to control the
whole computer with accessibility gestures and it's quite possible a gesture
could result in closing a Window. What's your concern exactly?

[tdresser, 2014/06/25 15:57:31]

That would make things tricky.

If GetAndResetPendingGestures returns several gestures, and one of them destroys
a window, the later gestures will try to target to the destroyed Window. This
causes some nasty crashes. 

We process this list here:
https://code.google.com/p/chromium/codesearch#chromium/src/ui/aura/window_eve...
normally, and in that case, we check if the event target has been destroyed
after each gesture is sent, and stop processing gestures if that is the case.

[tdresser, 2014/06/25 16:06:12]

Though depending on how you target the command to destroy the window, it might
work fine.

+    }
+  }
   state_ = NO_FINGERS_DOWN;
   initial_touch_id_passthrough_mapping_ = kTouchIdUnassigned;
   VLOG_STATE();
@@ -487,6 +604,8 @@ const char* TouchExplorationController::EnumStateToString(State state) {
       return "DOUBLE_TAP_PRESSED";
     case TOUCH_EXPLORATION:
       return "TOUCH_EXPLORATION";
+    case GESTURE_IN_PROGRESS:
+      return "GESTURE_IN_PROGRESS";
     case PASSTHROUGH_MINUS_ONE:
       return "PASSTHROUGH_MINUS_ONE";
     case TOUCH_EXPLORE_SECOND_PRESS: