Support double-tap to click in touch accessibility controller.

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 "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"
 
 namespace ui {
 
 TouchExplorationController::TouchExplorationController(
     aura::Window* root_window)
-        : root_window_(root_window) {
+      : root_window_(root_window),
+        initial_touch_id_passthrough_mapping_(0),
+        state_(NO_FINGERS_DOWN),
+        event_handler_for_testing_(NULL) {
   CHECK(root_window);
   root_window->GetHost()->GetEventSource()->AddEventRewriter(this);
 }
 
 TouchExplorationController::~TouchExplorationController() {
   root_window_->GetHost()->GetEventSource()->RemoveEventRewriter(this);
 }
 
+void TouchExplorationController::CallTapTimerNowForTesting() {
+  CHECK(tap_timer_.IsRunning());

[James Cook, 2014/06/05 18:04:41]

Could this be a DCHECK?

[dmazzoni, 2014/06/05 23:32:24]

OK. Honest question, though - how many people run Chrome OS with DCHECKs
enabled? I always use a release build on my device, I only test debug when
running locally on my desktop - which isn't helpful for touch.

[James Cook, 2014/06/06 00:09:45]

No one runs Chrome OS in debug. However, this function is only used for testing,
and unit tests are run in debug on the waterfall linux_chromeos builds, so
DCHECK seems good for test code.  Also, I don't know if the compiler is smart
enough to strip out unused *ForTesting() functions in shipping builds, but using
DCHECK ensures that our shipping code size doesn't increase as much.

[dmazzoni, 2014/06/06 15:27:22]

Ah, of course - I wasn't thinking about this being test-only. Thanks.

+  tap_timer_.Stop();
+  OnTapTimerFired();
+}
+
+void TouchExplorationController::SetEventHandlerForTesting(
+    ui::EventHandler* event_handler_for_testing) {
+  event_handler_for_testing_ = event_handler_for_testing;
+}
+
 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.
+  }
+
   const ui::EventType type = touch_event.type();
   const gfx::PointF& location = touch_event.location_f();
   const int touch_id = touch_event.touch_id();
-  const int flags = touch_event.flags();
-
-  if (type == ui::ET_TOUCH_PRESSED) {
-    touch_ids_.push_back(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) {
+    current_touch_ids_.push_back(touch_id);
     touch_locations_.insert(std::pair<int, gfx::PointF>(touch_id, location));
-    // If this is the first and only finger touching - rewrite the touch as a
-    // mouse move. Otherwise let the it go through as is.
-    if (touch_ids_.size() == 1) {
-      *rewritten_event = CreateMouseMoveEvent(location, flags);
+  } else if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
+    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);
+    touch_locations_.erase(touch_id);
+  } else if (type == ui::ET_TOUCH_MOVED) {
+    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;
+
+    touch_locations_[*it] = location;
+  }
+
+  // The rest of the processing depends on what state we're in.
+  switch(state_) {
+    case NO_FINGERS_DOWN:
+      return OnNoFingersDown(touch_event, rewritten_event);
+    case SINGLE_TAP_PRESSED:
+      return OnSingleTapPressed(touch_event, rewritten_event);
+    case SINGLE_TAP_RELEASED:
+      return OnSingleTapReleased(touch_event, rewritten_event);
+    case DOUBLE_TAP_PRESSED:
+      return OnDoubleTapPressed(touch_event, rewritten_event);
+    case TOUCH_EXPLORATION:
+      return OnTouchExploration(touch_event, rewritten_event);
+    case PASSTHROUGH_MINUS_ONE:
+      return OnPassthroughMinusOne(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::OnNoFingersDown(
+    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));
+    tap_timer_.Start(FROM_HERE,
+                     gesture_detector_config_.double_tap_timeout,
+                     this,
+                     &TouchExplorationController::OnTapTimerFired);
+    state_ = SINGLE_TAP_PRESSED;
+    return ui::EVENT_REWRITE_DISCARD;
+  }
+
+  NOTREACHED();
+  return ui::EVENT_REWRITE_CONTINUE;
+}
+
+ui::EventRewriteStatus TouchExplorationController::OnSingleTapPressed(

[James Cook, 2014/06/05 18:04:41]

optional: What do you think of naming these methods InSingleTapPressed() or
RewriteForSingleTapPressed() or SingleTapPressedState() instead of
OnSingleTapPressed()? The current names make me think the function is called
like a callback when the tap event occurs, rather than any event happening while
in that state.

[dmazzoni, 2014/06/05 23:32:24]

Make sense. I'm fine with InSingleTapPressed, etc.

I left OnTapTimerFired with "On".

+    const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event) {
+  const ui::EventType type = event.type();
+
+  if (type == ui::ET_TOUCH_PRESSED) {
+    // Adding a second finger within the timeout period switches to
+    // passthrough.
+    state_ = PASSTHROUGH_MINUS_ONE;
+    return OnPassthroughMinusOne(event, rewritten_event);
+  } else if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
+    DCHECK_EQ(0U, current_touch_ids_.size());
+    state_ = SINGLE_TAP_RELEASED;
+    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();
-      return ui::EVENT_REWRITE_REWRITTEN;
+      state_ = TOUCH_EXPLORATION;
+      return OnTouchExploration(event, rewritten_event);
     }
-    return ui::EVENT_REWRITE_CONTINUE;
-  } else if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
-    std::vector<int>::iterator it =
-        std::find(touch_ids_.begin(), touch_ids_.end(), touch_id);
-    // We may fail to find the finger if the exploration mode was turned on
-    // while the user had some fingers touching the screen. We simply ignore
-    // those fingers for the purposes of event transformation.
-    if (it == touch_ids_.end())
-      return ui::EVENT_REWRITE_CONTINUE;
-    const bool first_finger_released = it == touch_ids_.begin();
-    touch_ids_.erase(it);
-    int num_erased = touch_locations_.erase(touch_id);
-    DCHECK_EQ(num_erased, 1);
-    const int num_fingers_remaining = touch_ids_.size();
-
-    if (num_fingers_remaining == 0) {
-      *rewritten_event = CreateMouseMoveEvent(location, flags);
-      return ui::EVENT_REWRITE_REWRITTEN;
-    }
-
-    // If we are left with one finger - enter the mouse move mode.
-    const bool enter_mouse_move_mode = num_fingers_remaining == 1;
-
-    if (!enter_mouse_move_mode && !first_finger_released) {
-      // No special handling needed.
-      return ui::EVENT_REWRITE_CONTINUE;
-    }
-
-    // If the finger which was released was the first one, - we need to rewrite
-    // the release event as a release of the was second / now first finger.
-    // This is the finger which will now be getting "substracted".
-    if (first_finger_released) {
-      int rewritten_release_id = touch_ids_[0];
-      const gfx::PointF& rewritten_release_location =
-          touch_locations_[rewritten_release_id];
-      ui::TouchEvent* rewritten_release_event = new ui::TouchEvent(
-          ui::ET_TOUCH_RELEASED,
-          rewritten_release_location,
-          rewritten_release_id,
-          event.time_stamp());
-      rewritten_release_event->set_flags(touch_event.flags());
-      rewritten_event->reset(rewritten_release_event);
-    } else if (enter_mouse_move_mode) {
-      // Dispatch the release event as is.
-      // TODO(mfomitchev): We can get rid of this clause once we have
-      // EVENT_REWRITE_DISPATCH_ANOTHER working without having to set
-      // rewritten_event.
-      rewritten_event->reset(new ui::TouchEvent(touch_event));
-    }
-
-    if (enter_mouse_move_mode) {
-      // Since we are entering the mouse move mode - also dispatch a mouse move
-      // event at the location of the one remaining finger. (num_fingers == 1)
-      const gfx::PointF& mouse_move_location = touch_locations_[touch_ids_[0]];
-      next_dispatch_event_ =
-          CreateMouseMoveEvent(mouse_move_location, flags).Pass();
-      return ui::EVENT_REWRITE_DISPATCH_ANOTHER;
-    }
+
+    return EVENT_REWRITE_DISCARD;
+  }
+  NOTREACHED() << "Unexpected event type received.";
+  return ui::EVENT_REWRITE_CONTINUE;
+}
+
+ui::EventRewriteStatus TouchExplorationController::OnSingleTapReleased(
+    const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event) {
+  const ui::EventType type = event.type();
+  if (type == ui::ET_TOUCH_PRESSED) {
+    // This is the second tap in a double-tap (or double tap-hold).
+    // Rewrite at location of last touch exploration.
+    ui::TouchEvent* rewritten_press_event = new ui::TouchEvent(
+        ui::ET_TOUCH_PRESSED,
+        last_touch_exploration_location_,
+        event.touch_id(),
+        event.time_stamp());
+    rewritten_press_event->set_flags(event.flags());
+    rewritten_event->reset(rewritten_press_event);
+    state_ = DOUBLE_TAP_PRESSED;
+    return ui::EVENT_REWRITE_REWRITTEN;
+  }
+
+  NOTREACHED();
+  return ui::EVENT_REWRITE_CONTINUE;
+}
+
+ui::EventRewriteStatus TouchExplorationController::OnDoubleTapPressed(
+    const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event) {
+  const ui::EventType type = event.type();
+  if (type == ui::ET_TOUCH_PRESSED) {
+    return ui::EVENT_REWRITE_DISCARD;
+  } else if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
+    if (current_touch_ids_.size() != 0)
+      return EVENT_REWRITE_DISCARD;
+
+    // Rewrite at location of last touch exploration.
+    ui::TouchEvent* rewritten_release_event = new ui::TouchEvent(
+        ui::ET_TOUCH_RELEASED,
+        last_touch_exploration_location_,
+        event.touch_id(),
+        event.time_stamp());
+    rewritten_release_event->set_flags(event.flags());
+    rewritten_event->reset(rewritten_release_event);
+    ResetToNoFingersDown();
     return ui::EVENT_REWRITE_REWRITTEN;
   } else if (type == ui::ET_TOUCH_MOVED) {
-    std::vector<int>::iterator it =
-        std::find(touch_ids_.begin(), touch_ids_.end(), touch_id);
-    // We may fail to find the finger if the exploration mode was turned on
-    // while the user had some fingers touching the screen. We simply ignore
-    // those fingers for the purposes of event transformation.
-    if (it == touch_ids_.end())
-      return ui::EVENT_REWRITE_CONTINUE;
-    touch_locations_[*it] = location;
-    if (touch_ids_.size() == 1) {
-      // Touch moves are rewritten as mouse moves when there's only one finger
-      // touching the screen.
-      *rewritten_event = CreateMouseMoveEvent(location, flags).Pass();
-      return ui::EVENT_REWRITE_REWRITTEN;
+    return ui::EVENT_REWRITE_DISCARD;
+  }
+  NOTREACHED() << "Unexpected event type received.";
+  return ui::EVENT_REWRITE_CONTINUE;
+}
+
+ui::EventRewriteStatus TouchExplorationController::OnTouchExploration(
+    const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event) {
+  const ui::EventType type = event.type();
+  if (type == ui::ET_TOUCH_PRESSED) {
+    // Ignore any additional fingers when we're already in touch exploration
+    // mode. TODO(evy, lisayin): Support "split-tap" here instead.
+    return ui::EVENT_REWRITE_DISCARD;
+  } else if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
+    if (current_touch_ids_.size() == 0)
+      ResetToNoFingersDown();
+  } else if (type != ui::ET_TOUCH_MOVED) {
+    NOTREACHED() << "Unexpected event type received.";
+    return ui::EVENT_REWRITE_CONTINUE;
+  }
+
+  // Rewrite as a mouse-move event.
+  *rewritten_event = CreateMouseMoveEvent(event.location(), event.flags());
+  last_touch_exploration_location_ = event.location();
+  return ui::EVENT_REWRITE_REWRITTEN;
+}
+
+ui::EventRewriteStatus TouchExplorationController::OnPassthroughMinusOne(
+    const ui::TouchEvent& event, scoped_ptr<ui::Event>* rewritten_event) {
+  ui::EventType type = event.type();
+  gfx::PointF location = event.location_f();
+
+  if (type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED) {
+    if (current_touch_ids_.size() == 0)
+      ResetToNoFingersDown();
+
+    if (initial_touch_id_passthrough_mapping_ == 0) {
+      if (event.touch_id() == initial_press_->touch_id()) {
+        initial_touch_id_passthrough_mapping_ = -1;

[James Cook, 2014/06/05 18:04:41]

Use a named constant instead of -1.

[dmazzoni, 2014/06/05 23:32:24]

Done.

+      } else {
+        // If the only finger now remaining is the first finger,
+        // rewrite as a move to the location of the first finger.
+        initial_touch_id_passthrough_mapping_ = event.touch_id();
+        ui::TouchEvent* rewritten_passthrough_event = new ui::TouchEvent(
+            ui::ET_TOUCH_MOVED,
+            touch_locations_[initial_press_->touch_id()],
+            initial_touch_id_passthrough_mapping_,
+            event.time_stamp());
+        rewritten_passthrough_event->set_flags(event.flags());
+        rewritten_event->reset(rewritten_passthrough_event);
+        return ui::EVENT_REWRITE_REWRITTEN;
+      }
     }
-    if (touch_id == touch_ids_.front()) {
-      // Touch moves of the first finger are discarded when there's more than
-      // one finger touching.
+  }
+
+  if (event.touch_id() == initial_press_->touch_id()) {
+    if (initial_touch_id_passthrough_mapping_ <= 0)

[James Cook, 2014/06/05 18:04:41]

Could compare directly to your named constant, since I presume this is checking
for the -1 case.

[dmazzoni, 2014/06/05 23:32:24]

Done.

       return ui::EVENT_REWRITE_DISCARD;
-    }
-    return ui::EVENT_REWRITE_CONTINUE;
-  }
-  NOTREACHED() << "Unexpected event type received.";
-  return ui::EVENT_REWRITE_CONTINUE;
-}
-
-ui::EventRewriteStatus TouchExplorationController::NextDispatchEvent(
-    const ui::Event& last_event,
-    scoped_ptr<ui::Event>* new_event) {
-  CHECK(next_dispatch_event_);
-  DCHECK(last_event.IsTouchEvent());
-  *new_event = next_dispatch_event_.Pass();
-  // Enter the mouse move mode if needed
-  if ((*new_event)->IsMouseEvent())
+
+    ui::TouchEvent* rewritten_passthrough_event = new ui::TouchEvent(
+        type,
+        location,
+        initial_touch_id_passthrough_mapping_,
+        event.time_stamp());
+    rewritten_passthrough_event->set_flags(event.flags());
+    rewritten_event->reset(rewritten_passthrough_event);
+    return ui::EVENT_REWRITE_REWRITTEN;
+  }
+
+  return ui::EVENT_REWRITE_CONTINUE;
+}
+
+void TouchExplorationController::OnTapTimerFired() {
+  if (state_ != SINGLE_TAP_RELEASED && state_ != SINGLE_TAP_PRESSED)
+    return;
+
+  if (state_ == SINGLE_TAP_RELEASED) {
+    ResetToNoFingersDown();
+  } else {
     EnterTouchToMouseMode();
-  return ui::EVENT_REWRITE_REWRITTEN;
+    state_ = TOUCH_EXPLORATION;
+  }
+
+  scoped_ptr<ui::Event> mouse_move = CreateMouseMoveEvent(
+      initial_press_->location(), initial_press_->flags());
+  DispatchEvent(mouse_move.get());
+  last_touch_exploration_location_ = initial_press_->location();
+}
+
+void TouchExplorationController::DispatchEvent(ui::Event* event) {
+  if (event_handler_for_testing_) {
+    event_handler_for_testing_->OnEvent(event);
+    return;
+  }
+
+  ui::EventDispatchDetails result ALLOW_UNUSED =
+      root_window_->GetHost()->dispatcher()->OnEventFromSource(event);
 }
 
 scoped_ptr<ui::Event> TouchExplorationController::CreateMouseMoveEvent(
     const gfx::PointF& location,
     int flags) {
   return scoped_ptr<ui::Event>(
       new ui::MouseEvent(
           ui::ET_MOUSE_MOVED,
           location,
           location,
           flags | ui::EF_IS_SYNTHESIZED | ui::EF_TOUCH_ACCESSIBILITY,
           0));
 }
 
 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() {
+  state_ = NO_FINGERS_DOWN;
+  initial_touch_id_passthrough_mapping_ = 0;
+  if (tap_timer_.IsRunning())
+    tap_timer_.Stop();
+}
+
 }  // namespace ui