Corner Passthrough 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 0a63014062c19cbb9580426b5854b23c3a2008b7..233f544b8d6c0a5c735df55483c1083800b86279 100644
--- a/ui/chromeos/touch_exploration_controller.cc
+++ b/ui/chromeos/touch_exploration_controller.cc
@@ -23,6 +23,10 @@ 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(500);
+
 // In ChromeOS, VKEY_LWIN is synonymous for the search key.
 const ui::KeyboardCode kChromeOSSearchKey = ui::VKEY_LWIN;
 }  // namespace
@@ -36,7 +40,8 @@ TouchExplorationController::TouchExplorationController(
       event_handler_for_testing_(NULL),
       gesture_provider_(this),
       prev_state_(NO_FINGERS_DOWN),
-      VLOG_on_(true) {
+      VLOG_on_(true),
+      waiting_for_corner_passthrough_(false) {
   CHECK(root_window);
   root_window->GetHost()->GetEventSource()->AddEventRewriter(this);
 }
@@ -132,6 +137,8 @@ ui::EventRewriteStatus TouchExplorationController::RewriteEvent(
       return InTouchExploreSecondPress(touch_event, rewritten_event);
     case TWO_TO_ONE_FINGER:
       return InTwoToOneFinger(touch_event, rewritten_event);
+    case CORNER_PASSTHROUGH:
+      return InCornerPassthrough(touch_event, rewritten_event);
     case PASSTHROUGH:
       return InPassthrough(touch_event, rewritten_event);
     case WAIT_FOR_RELEASE:
@@ -152,28 +159,60 @@ ui::EventRewriteStatus TouchExplorationController::NextDispatchEvent(
 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));
-    tap_timer_.Start(FROM_HERE,
-                     gesture_detector_config_.double_tap_timeout,
-                     this,
-                     &TouchExplorationController::OnTapTimerFired);
-    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) {
+    VLOG(0) << "Location: " << location;
+    timeout = kCornerPassthroughDelay;
+    waiting_for_corner_passthrough_ = true;
+  } else {
+    timeout = gesture_detector_config_.double_tap_timeout;
+    waiting_for_corner_passthrough_ = false;
+  }
+
+  initial_press_.reset(new TouchEvent(event));
+  last_unused_finger_event_.reset(new TouchEvent(event));
+  tap_timer_.Start(
+      FROM_HERE, timeout, this, &TouchExplorationController::OnTapTimerFired);
+  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) {

[aboxhall, 2014/07/24 18:26:34]

I think |in_a_bottom_corner| should be negated...

[lisayin, 2014/07/25 20:11:57]

Opps...

+    waiting_for_corner_passthrough_ = false;
+    // If the initial press was in a corner, then more than the double tap
+    // timeout could have elapsed.
+    if (tap_timer_.IsRunning() &&
+        event.time_stamp() - initial_press_->time_stamp() >
+            gesture_detector_config_.double_tap_timeout) {
+      tap_timer_.Stop();
+      OnTapTimerFired();
+      return EVENT_REWRITE_DISCARD;
+    }
+  }
+
   if (type == ui::ET_TOUCH_PRESSED) {
     // Adding a second finger within the timeout period switches to
     // passing through every event from the second finger and none form the
@@ -402,7 +441,7 @@ ui::EventRewriteStatus TouchExplorationController::InTwoToOneFinger(
     // If a third finger is pressed, we are now going into passthrough mode
     // and now need to dispatch the first finger into a press, as well as the
     // recent press.
-    if (current_touch_ids_.size() == 3){
+    if (current_touch_ids_.size() == 3) {
       state_ = PASSTHROUGH;
       scoped_ptr<ui::TouchEvent> first_finger_press;
       first_finger_press.reset(
@@ -441,6 +480,33 @@ ui::EventRewriteStatus TouchExplorationController::InTwoToOneFinger(
   return ui::EVENT_REWRITE_CONTINUE;
 }
 
+ui::EventRewriteStatus TouchExplorationController::InCornerPassthrough(
+    const ui::TouchEvent& event,
+    scoped_ptr<ui::Event>* rewritten_event) {
+  ui::EventType type = event.type();
+  if (current_touch_ids_.size() == 0) {
+    ResetToNoFingersDown();
+  }
+
+  if (event.touch_id() == initial_press_->touch_id()) {

[aboxhall, 2014/07/24 18:26:34]

Some comments explaining this block would be helpful. I gather it's detecting
where you've slightly moved the original finger within the corner and discarding
that event, and also discarding any events on that finger which follow from
moving it out of the corner?

[lisayin, 2014/07/25 20:11:57]

Done.

+    int edge = FindEdgesWithinBounds(event.location(), kSlopDistanceFromEdge);

[aboxhall, 2014/07/24 18:26:34]

suggestion: s/edge/edges/

[lisayin, 2014/07/25 20:11:57]

Done.

+    bool in_a_bottom_corner = (edge == BOTTOM_LEFT_CORNER) ||
+                              (edge == BOTTOM_RIGHT_CORNER);
+    if (type == ui::ET_TOUCH_MOVED && in_a_bottom_corner)
+      return ui::EVENT_REWRITE_DISCARD;
+
+    waiting_for_corner_passthrough_ = false;
+    state_ = WAIT_FOR_RELEASE;
+    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());
+
+  return ui::EVENT_REWRITE_REWRITTEN;
+}
+
 ui::EventRewriteStatus TouchExplorationController::InPassthrough(
     const ui::TouchEvent& event,
     scoped_ptr<ui::Event>* rewritten_event) {
@@ -586,6 +652,14 @@ ui::EventRewriteStatus TouchExplorationController::InSlideGesture(
 }
 
 void TouchExplorationController::OnTapTimerFired() {
+  if (waiting_for_corner_passthrough_) {
+    delegate_->PlayEarCon();
+    delete gesture_provider_.GetAndResetPendingGestures();
+    state_ = CORNER_PASSTHROUGH;
+    VLOG_STATE();
+    return;
+  }
+
   switch (state_) {
     case SINGLE_TAP_RELEASED:
       ResetToNoFingersDown();
@@ -805,6 +879,7 @@ void TouchExplorationController::EnterTouchToMouseMode() {
 }
 
 void TouchExplorationController::ResetToNoFingersDown() {
+  waiting_for_corner_passthrough_ = false;
   ProcessGestureEvents();
   if (sound_timer_.IsRunning())
     sound_timer_.Stop();
@@ -875,6 +950,8 @@ const char* TouchExplorationController::EnumStateToString(State state) {
       return "TOUCH_EXPLORE_SECOND_PRESS";
     case TWO_TO_ONE_FINGER:
       return "TWO_TO_ONE_FINGER";
+    case CORNER_PASSTHROUGH:
+      return "CORNER_PASSTHROUGH";
     case PASSTHROUGH:
       return "PASSTHROUGH";
     case WAIT_FOR_RELEASE: