Controller support for VrShell

chrome/browser/android/vr_shell/vr_controller.cc

+// Copyright 2016 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 "chrome/browser/android/vr_shell/vr_controller.h"
+
+#include <android/log.h>
+
+#include <cmath>
+
+#include "base/logging.h"
+#include "third_party/WebKit/public/web/WebInputEvent.h"
+
+using blink::WebInputEvent;
+
+namespace vr_shell {
+
+namespace {
+constexpr float kDisplacementScaleFactor = 800.0f;

[tdresser, 2016/09/23 13:48:18]

Add comment explaining what this is.

[asimjour, 2016/09/23 16:58:20]

This is a temporary scaling factor that should be replaced later on when we have
access to the details of the touchpad. This scaling is usually is done by
Operating system, but in this case OS only reports raw data.

+
+// A slop represents a small rectangular region around the first touch point of
+// a gesture.
+// If the user does not move outside of the slop, no gesture is detected.
+// Gestures start to be detected when the user moves outside of the slop.
+// Vertical distance from the border to the center of slop.
+constexpr float kSlopVertical = 0.165f;
+
+// Horizontal distance from the border to the center of slop.
+constexpr float kSlopHorizontal = 0.125f;

[tdresser, 2016/09/23 13:48:18]

Why are vertical and horizontal not equal? Why use a rectangle instead of a
circle?

[asimjour, 2016/09/23 16:58:20]

The constants are picked by UX team based on user study.

+constexpr float kDelta = 1.0e-7f;

[tdresser, 2016/09/23 13:48:19]

What is this?

[asimjour, 2016/09/23 16:58:20]

Two vectors with this distance are considered to be equal.

+
+constexpr float kMinZoomAngle = 0.25f;

[tdresser, 2016/09/23 13:48:18]

What is this?

[asimjour, 2016/09/23 16:58:20]

Minimum angle that required for zoom gesture. It is about the orientation of the
controller, and it's not related to touch events.

+
+inline void ClampTouchpadPosition(gvr::Vec2f* position) {
+  position->x = std::min(std::max(0.0f, position->x), 1.0f);
+  position->y = std::min(std::max(0.0f, position->y), 1.0f);
+}
+
+inline void VectSetZero(gvr::Vec2f* v) {
+  v->x = 0;
+  v->y = 0;
+}
+
+inline gvr::Vec2f VectSubtract(gvr::Vec2f v1, gvr::Vec2f v2) {
+  gvr::Vec2f result;
+  result.x = v1.x - v2.x;
+  result.y = v1.y - v2.y;
+  return result;
+}
+
+inline bool VectEqual(const gvr::Vec2f v1, const gvr::Vec2f v2) {
+  return (std::abs(v1.x - v2.x) < kDelta) && (std::abs(v1.y - v2.y) < kDelta);
+}

[tdresser, 2016/09/23 13:48:18]

All this code would go away if we used Vector2dF, wouldn't it?

+
+}  // namespace
+
+VrController::VrController(gvr_context* vr_context) {
+  Initialize(vr_context);
+  Reset();
+}
+
+VrController::~VrController() {}
+
+void VrController::OnResume() {
+  if (controller_api_)
+    controller_api_->Resume();
+}
+
+void VrController::OnPause() {
+  if (controller_api_)
+    controller_api_->Pause();
+}
+
+bool VrController::IsTouching() {
+  return controller_state_.IsTouching();
+}
+
+float VrController::TouchPosX() {
+  return controller_state_.GetTouchPos().x;
+}
+
+float VrController::TouchPosY() {
+  return controller_state_.GetTouchPos().y;
+}

[tdresser, 2016/09/23 13:48:18]

Why doesn't this return a Vector2dF?

+
+const gvr::Quatf VrController::Orientation() {
+  return controller_state_.GetOrientation();
+}
+
+bool VrController::IsTouchDown() {
+  return controller_state_.GetTouchDown();
+}
+
+bool VrController::IsTouchUp() {
+  return controller_state_.GetTouchUp();
+}
+
+bool VrController::ButtonDown(const int32_t button) {

[bshe, 2016/09/22 23:16:48]

nit: IsButtonDown?

[asimjour, 2016/09/23 16:58:20]

Done.

+  return controller_state_.GetButtonDown(button);
+}
+
+bool VrController::ButtonUp(const int32_t button) {

[bshe, 2016/09/22 23:16:49]

nit: IsButtonUp

[asimjour, 2016/09/23 16:58:20]

Done.

+  return controller_state_.GetButtonUp(button);
+}
+
+bool VrController::IsConnected() {
+  return controller_state_.GetConnectionState() == gvr::kControllerConnected;
+}
+
+void VrController::UpdateState() {
+  const int32_t old_status = controller_state_.GetApiStatus();
+  const int32_t old_connection_state = controller_state_.GetConnectionState();
+  // Read current controller state.
+  controller_state_.Update(*controller_api_);

[bshe, 2016/09/22 23:16:48]

If controller is not connected, what would Update do?

[asimjour, 2016/09/23 16:58:20]

UpdateState only updates the state of the controller regarding to the
connectivity. If the controller is not connected, the
controller_state_.GetConnectionState() will indicate that, so the controller
won't generate any gestures.

+  // Print new API status and connection state, if they changed.
+  if (controller_state_.GetApiStatus() != old_status ||
+      controller_state_.GetConnectionState() != old_connection_state) {
+    VLOG(1) << "Controller Connection status: "
+            << gvr_controller_connection_state_to_string(
+                   controller_state_.GetConnectionState());
+  }
+  return;

[bshe, 2016/09/22 23:16:49]

nit: unnecessary return

[asimjour, 2016/09/23 16:58:20]

Done.

+}
+
+void VrController::Update(bool touch_up,
+                          bool touch_down,
+                          bool is_touching,
+                          const gvr::Vec2f position,
+                          int64_t timestamp) {
+  CHECK(touch_info_ != nullptr) << "touch_info_ not initialized properly.";
+  touch_info_->touch_up = touch_up;
+  touch_info_->touch_down = touch_down;
+  touch_info_->is_touching = is_touching;
+  touch_info_->touch_point.position = position;
+  ClampTouchpadPosition(&touch_info_->touch_point.position);
+  touch_info_->touch_point.timestamp = timestamp;
+
+  UpdateGestureFromTouchInfo();
+}
+
+void VrController::Initialize(gvr_context* gvr_context) {
+  CHECK(gvr_context != nullptr) << "invalid gvr_context";
+  controller_api_.reset(new gvr::ControllerApi);
+  int32_t options = gvr::ControllerApi::DefaultOptions();
+
+  // Enable non-default options, if you need them:
+  // options |= GVR_CONTROLLER_ENABLE_GYRO;
+  CHECK(controller_api_->Init(options, gvr_context));
+  controller_api_->Resume();
+}
+
+VrGesture VrController::DetectGesture() {
+  if (controller_state_.GetConnectionState() == gvr::kControllerConnected) {
+    gvr::Vec2f position;
+    position.x = TouchPosX();
+    position.y = TouchPosY();
+    Update(IsTouchUp(), IsTouchDown(), IsTouching(), position,
+           gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos);
+    if (GetGestureListSize() > 0 &&
+        GetGesturePtr(0)->type == kGestureTypeScroll) {
+      switch (GetGesturePtr(0)->details.scroll.state) {
+        case WebInputEvent::GestureScrollBegin:
+          return VrGesture(

[tdresser, 2016/09/23 13:48:18]

If I understand correctly, we perform gesture detection to come up with some
WebInputEvents, and then we immediately turn them into VrGestures? 

Why don't we use WebInputEvents throughout?

Barring that, why not just construct VrGestures immediately?

[asimjour, 2016/09/23 16:58:20]

Our gestures are not limited to the gestures that are supported by
WebInputEvents. We have to use VrGesture to be able to expand the gesture set.

[tdresser, 2016/09/23 17:45:17]

So why not construct VREvents immediately instead of temporarily using
WebInputEvents?

[asimjour, 2016/09/23 19:56:31]

Only constants regarding the state of the gesture are borrowed from
WebInputEvent to avoid introducing similar constant twice.
For VrGestures that are VR specific these constant are not needed. So we define
a new set of constant, it will be identical to WebInputEvents.
However, it means if we remove the first argument and don't use VrGesture, we
have to add our additional gestures to WebInputEvent, which is not possible.

[tdresser, 2016/09/23 20:36:44]

Which constants? Just the types? Don't we already have copies of the types?

+              kGestureScroll,
+              gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+              gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+              GetGesturePtr(0)->displacement.x * kDisplacementScaleFactor,
+              GetGesturePtr(0)->displacement.y * kDisplacementScaleFactor,
+              WebInputEvent::GestureScrollBegin, Orientation());
+        case WebInputEvent::GestureScrollUpdate:
+          return VrGesture(
+              kGestureScroll,
+              gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+              gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+              GetGesturePtr(0)->displacement.x * kDisplacementScaleFactor,
+              GetGesturePtr(0)->displacement.y * kDisplacementScaleFactor,
+              WebInputEvent::GestureScrollUpdate, Orientation());
+        case WebInputEvent::GestureScrollEnd:
+          return VrGesture(
+              kGestureScroll,
+              gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+              gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+              GetGesturePtr(0)->displacement.x * kDisplacementScaleFactor,
+              GetGesturePtr(0)->displacement.y * kDisplacementScaleFactor,
+              WebInputEvent::GestureScrollEnd, Orientation());
+      }
+    }
+
+    if (ButtonDown(gvr::kControllerButtonClick)) {
+      return VrGesture(
+          kGestureButtonsChange,
+          gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+          gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos, 1, 0,
+          Orientation());
+    }
+    float dqx = 0.0f;
+
+    dqx = last_qx_ - Orientation().qx;
+
+    // don't accept rapid moves
+    if (dqx < -1.0f || dqx > 1.0f)
+      dqx = 0.0f;
+    last_qx_ = Orientation().qx;
+
+    if (ButtonDown(gvr::kControllerButtonApp))
+      zoom_in_progress_ = true;
+    if (ButtonUp(gvr::kControllerButtonApp)) {
+      zoom_in_progress_ = false;
+      if (pinch_started_) {
+        pinch_started_ = false;
+      }
+    }
+    if (zoom_in_progress_) {
+      if (dqx != 0.0f) {
+        // dz == 1 means no zoom. dz < 1 means zoom-out and dz > 1 means
+        // zoom-in.
+        // dqx * 2 + 1 results to dz \in [0,2]
+        return VrGesture(
+            kGestureZoom,
+            gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+            gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+            dqx * 2 + 1, Orientation());
+      }
+      if (Orientation().qz < kMinZoomAngle &&
+          Orientation().qz > -1 * kMinZoomAngle && pinch_started_) {
+        pinch_started_ = false;
+      }
+    }
+    return VrGesture(kGestureAngularMove,
+                     gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+                     gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos,
+                     Orientation());
+  }
+  return VrGesture();
+}
+
+void VrController::UpdateGestureFromTouchInfo() {
+  // Clear the gesture list.
+  gesture_list_.clear();
+
+  switch (state_) {
+    // user has not put finger on touch pad.

[tdresser, 2016/09/23 20:36:44]

Capitalize comments.

+    case WAITING:
+      HandleWaitingState();
+      break;
+    // user has not started a gesture (by moving out of slop).
+    case TOUCHING:
+      HandleDetectingState();
+      break;
+    // user is scrolling on touchpad
+    case SCROLLING:
+      HandleScrollingState();
+      break;
+    default:
+      LOG(ERROR) << "Wrong gesture detector state: " << state_;
+      break;
+  }
+}
+
+const VrGesture* VrController::GetGesturePtr(const size_t index) {
+  CHECK(index < gesture_list_.size()) << "The gesture index exceeds the"
+                                         "size of gesture list.";
+  return const_cast<VrGesture*>(&gesture_list_[index]);
+}
+
+void VrController::Update(const gvr_controller_state* controller_state) {
+  // Update touch information.
+  CHECK(touch_info_ != nullptr) << "touch_info_ not initialized properly.";
+  touch_info_->touch_up = gvr_controller_state_get_touch_up(controller_state);
+  touch_info_->touch_down =
+      gvr_controller_state_get_touch_down(controller_state);
+  touch_info_->is_touching = gvr_controller_state_is_touching(controller_state);
+  touch_info_->touch_point.position.x =
+      gvr_controller_state_get_touch_pos(controller_state).x;
+  touch_info_->touch_point.position.y =
+      gvr_controller_state_get_touch_pos(controller_state).y;
+  ClampTouchpadPosition(&(touch_info_->touch_point.position));
+  touch_info_->touch_point.timestamp =
+      gvr_controller_state_get_last_touch_timestamp(controller_state);
+
+  UpdateGestureFromTouchInfo();
+}
+
+void VrController::HandleWaitingState() {
+  // User puts finger on touch pad (or when the touch down for current gesture
+  // is missed, initiate gesture from current touch point).
+  if (touch_info_->touch_down || touch_info_->is_touching) {
+    // update initial touchpoint
+    *init_touch_point_ = touch_info_->touch_point;
+    // update current touchpoint
+    *cur_touch_point_ = touch_info_->touch_point;
+    state_ = TOUCHING;
+  }
+}
+
+void VrController::HandleDetectingState() {
+  // User lifts up finger from touch pad.
+  if (touch_info_->touch_up || !(touch_info_->is_touching)) {
+    Reset();
+    return;
+  }
+
+  // Touch position is changed and the touch point moves outside of slop.
+  if (UpdateCurrentTouchpoint() && touch_info_->is_touching &&
+      !InSlop(touch_info_->touch_point.position)) {
+    state_ = SCROLLING;
+    VrGesture gesture;
+    gesture.type = kGestureTypeScroll;
+    gesture.details.scroll.state = WebInputEvent::GestureScrollBegin;
+    UpdateGesture(&gesture);
+    gesture_list_.push_back(gesture);
+  }
+}
+
+void VrController::HandleScrollingState() {
+  // Update current touch point.
+  bool touch_position_changed = UpdateCurrentTouchpoint();
+  if (touch_info_->touch_up || !(touch_info_->is_touching)) {  // gesture ends
+    VrGesture scroll_end;
+    scroll_end.type = kGestureTypeScroll;
+    scroll_end.details.scroll.state = WebInputEvent::GestureScrollEnd;
+    UpdateGesture(&scroll_end);
+    gesture_list_.push_back(scroll_end);
+
+    Reset();
+  } else if (touch_position_changed) {  // User continues scrolling and there is
+                                        // a change in touch position.
+    VrGesture scroll_update;
+    scroll_update.type = kGestureTypeScroll;
+    scroll_update.details.scroll.state = WebInputEvent::GestureScrollUpdate;
+    UpdateGesture(&scroll_update);
+    gesture_list_.push_back(scroll_update);
+  }
+}
+
+bool VrController::InSlop(const gvr::Vec2f touch_position) {
+  return (std::abs(touch_position.x - init_touch_point_->position.x) <
+          kSlopHorizontal) &&
+         (std::abs(touch_position.y - init_touch_point_->position.y) <
+          kSlopVertical);
+}
+
+void VrController::Reset() {
+  // Reset state.
+  state_ = WAITING;
+
+  // Reset the pointers.
+  prev_touch_point_.reset(new TouchPoint);
+  cur_touch_point_.reset(new TouchPoint);
+  init_touch_point_.reset(new TouchPoint);
+  touch_info_.reset(new TouchInfo);
+  VectSetZero(&overall_velocity_);
+}
+
+void VrController::UpdateGesture(VrGesture* gesture) {
+  if (!gesture)
+    LOG(ERROR) << "The gesture pointer is not initiated properly.";
+  gesture->velocity = overall_velocity_;
+  gesture->displacement =
+      VectSubtract(cur_touch_point_->position, prev_touch_point_->position);
+}
+
+bool VrController::UpdateCurrentTouchpoint() {
+  if (touch_info_->is_touching || touch_info_->touch_up) {
+    // Update the touch point when the touch position has changed.
+    if (!VectEqual(cur_touch_point_->position,
+                   touch_info_->touch_point.position)) {
+      prev_touch_point_.swap(cur_touch_point_);
+      *cur_touch_point_ = touch_info_->touch_point;
+
+      return true;
+    }
+  }
+  return false;
+}
+
+}  // namespace vr_shell