1 files changed, 219 insertions, 0 deletions
diff --git a/widget/cocoa/SwipeTracker.mm b/widget/cocoa/SwipeTracker.mm
new file mode 100644
index 0000000000..51169171a4
--- /dev/null
+++ b/widget/cocoa/SwipeTracker.mm
@@ -0,0 +1,219 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SwipeTracker.h"
+
+#include "InputData.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/TouchEvents.h"
+#include "nsAlgorithm.h"
+#include "nsChildView.h"
+#include "UnitTransforms.h"
+
+// These values were tweaked to make the physics feel similar to the native swipe.
+static const double kSpringForce = 250.0;
+static const double kVelocityTwitchTolerance = 0.0000001;
+static const double kWholePagePixelSize = 1000.0;
+static const double kRubberBandResistanceFactor = 4.0;
+static const double kSwipeSuccessThreshold = 0.25;
+static const double kSwipeSuccessVelocityContribution = 0.3;
+
+namespace mozilla {
+
+static already_AddRefed<nsRefreshDriver>
+GetRefreshDriver(nsIWidget& aWidget)
+{
+  nsIWidgetListener* widgetListener = aWidget.GetWidgetListener();
+  nsIPresShell* presShell = widgetListener ? widgetListener->GetPresShell() : nullptr;
+  nsPresContext* presContext = presShell ? presShell->GetPresContext() : nullptr;
+  RefPtr<nsRefreshDriver> refreshDriver = presContext ? presContext->RefreshDriver() : nullptr;
+  return refreshDriver.forget();
+}
+
+SwipeTracker::SwipeTracker(nsChildView& aWidget,
+                           const PanGestureInput& aSwipeStartEvent,
+                           uint32_t aAllowedDirections,
+                           uint32_t aSwipeDirection)
+  : mWidget(aWidget)
+  , mRefreshDriver(GetRefreshDriver(mWidget))
+  , mAxis(0.0, 0.0, 0.0, kSpringForce, 1.0)
+  , mEventPosition(RoundedToInt(ViewAs<LayoutDevicePixel>(aSwipeStartEvent.mPanStartPoint,
+                                  PixelCastJustification::LayoutDeviceIsScreenForUntransformedEvent)))
+  , mLastEventTimeStamp(aSwipeStartEvent.mTimeStamp)
+  , mAllowedDirections(aAllowedDirections)
+  , mSwipeDirection(aSwipeDirection)
+  , mGestureAmount(0.0)
+  , mCurrentVelocity(0.0)
+  , mEventsAreControllingSwipe(true)
+  , mEventsHaveStartedNewGesture(false)
+  , mRegisteredWithRefreshDriver(false)
+{
+  SendSwipeEvent(eSwipeGestureStart, 0, 0.0);
+  ProcessEvent(aSwipeStartEvent);
+}
+
+void
+SwipeTracker::Destroy()
+{
+  UnregisterFromRefreshDriver();
+}
+
+SwipeTracker::~SwipeTracker()
+{
+  MOZ_ASSERT(!mRegisteredWithRefreshDriver, "Destroy needs to be called before deallocating");
+}
+
+double
+SwipeTracker::SwipeSuccessTargetValue() const
+{
+  return (mSwipeDirection == nsIDOMSimpleGestureEvent::DIRECTION_RIGHT) ? -1.0 : 1.0;
+}
+
+double
+SwipeTracker::ClampToAllowedRange(double aGestureAmount) const
+{
+  // gestureAmount needs to stay between -1 and 0 when swiping right and
+  // between 0 and 1 when swiping left.
+  double min = (mSwipeDirection == nsIDOMSimpleGestureEvent::DIRECTION_RIGHT) ? -1.0 : 0.0;
+  double max = (mSwipeDirection == nsIDOMSimpleGestureEvent::DIRECTION_LEFT) ? 1.0 : 0.0;
+  return clamped(aGestureAmount, min, max);
+}
+
+bool
+SwipeTracker::ComputeSwipeSuccess() const
+{
+  double targetValue = SwipeSuccessTargetValue();
+
+  // If the fingers were moving away from the target direction when they were
+  // lifted from the touchpad, abort the swipe.
+  if (mCurrentVelocity * targetValue < -kVelocityTwitchTolerance) {
+    return false;
+  }
+
+  return (mGestureAmount * targetValue +
+          mCurrentVelocity * targetValue * kSwipeSuccessVelocityContribution) >= kSwipeSuccessThreshold;
+}
+
+nsEventStatus
+SwipeTracker::ProcessEvent(const PanGestureInput& aEvent)
+{
+  // If the fingers have already been lifted, don't process this event for swiping.
+  if (!mEventsAreControllingSwipe) {
+    // Return nsEventStatus_eConsumeNoDefault for events from the swipe gesture
+    // and nsEventStatus_eIgnore for events of subsequent scroll gestures.
+    if (aEvent.mType == PanGestureInput::PANGESTURE_MAYSTART ||
+        aEvent.mType == PanGestureInput::PANGESTURE_START) {
+      mEventsHaveStartedNewGesture = true;
+    }
+    return mEventsHaveStartedNewGesture ? nsEventStatus_eIgnore : nsEventStatus_eConsumeNoDefault;
+  }
+
+  double delta = -aEvent.mPanDisplacement.x / mWidget.BackingScaleFactor() / kWholePagePixelSize;
+  if (!SwipingInAllowedDirection()) {
+    delta /= kRubberBandResistanceFactor;
+  }
+  mGestureAmount = ClampToAllowedRange(mGestureAmount + delta);
+  SendSwipeEvent(eSwipeGestureUpdate, 0, mGestureAmount);
+
+  if (aEvent.mType != PanGestureInput::PANGESTURE_END) {
+    double elapsedSeconds = std::max(0.008, (aEvent.mTimeStamp - mLastEventTimeStamp).ToSeconds());
+    mCurrentVelocity = delta / elapsedSeconds;
+    mLastEventTimeStamp = aEvent.mTimeStamp;
+  } else {
+    mEventsAreControllingSwipe = false;
+    bool didSwipeSucceed = SwipingInAllowedDirection() && ComputeSwipeSuccess();
+    double targetValue = 0.0;
+    if (didSwipeSucceed) {
+      SendSwipeEvent(eSwipeGesture, mSwipeDirection, 0.0);
+      targetValue = SwipeSuccessTargetValue();
+    }
+    StartAnimating(targetValue);
+  }
+
+  return nsEventStatus_eConsumeNoDefault;
+}
+
+void
+SwipeTracker::StartAnimating(double aTargetValue)
+{
+  mAxis.SetPosition(mGestureAmount);
+  mAxis.SetDestination(aTargetValue);
+  mAxis.SetVelocity(mCurrentVelocity);
+
+  mLastAnimationFrameTime = TimeStamp::Now();
+
+  // Add ourselves as a refresh driver observer. The refresh driver
+  // will call WillRefresh for each animation frame until we
+  // unregister ourselves.
+  MOZ_ASSERT(!mRegisteredWithRefreshDriver);
+  if (mRefreshDriver) {
+    mRefreshDriver->AddRefreshObserver(this, Flush_Style);
+    mRegisteredWithRefreshDriver = true;
+  }
+}
+
+void
+SwipeTracker::WillRefresh(mozilla::TimeStamp aTime)
+{
+  TimeStamp now = TimeStamp::Now();
+  mAxis.Simulate(now - mLastAnimationFrameTime);
+  mLastAnimationFrameTime = now;
+
+  bool isFinished = mAxis.IsFinished(1.0 / kWholePagePixelSize);
+  mGestureAmount = (isFinished ? mAxis.GetDestination() : mAxis.GetPosition());
+  SendSwipeEvent(eSwipeGestureUpdate, 0, mGestureAmount);
+
+  if (isFinished) {
+    UnregisterFromRefreshDriver();
+    SwipeFinished();
+  }
+}
+
+void
+SwipeTracker::CancelSwipe()
+{
+  SendSwipeEvent(eSwipeGestureEnd, 0, 0.0);
+}
+
+void SwipeTracker::SwipeFinished()
+{
+  SendSwipeEvent(eSwipeGestureEnd, 0, 0.0);
+  mWidget.SwipeFinished();
+}
+
+void
+SwipeTracker::UnregisterFromRefreshDriver()
+{
+  if (mRegisteredWithRefreshDriver) {
+    MOZ_ASSERT(mRefreshDriver, "How were we able to register, then?");
+    mRefreshDriver->RemoveRefreshObserver(this, Flush_Style);
+  }
+  mRegisteredWithRefreshDriver = false;
+}
+
+/* static */ WidgetSimpleGestureEvent
+SwipeTracker::CreateSwipeGestureEvent(EventMessage aMsg, nsIWidget* aWidget,
+                                      const LayoutDeviceIntPoint& aPosition)
+{
+  WidgetSimpleGestureEvent geckoEvent(true, aMsg, aWidget);
+  geckoEvent.mModifiers = 0;
+  geckoEvent.mTimeStamp = TimeStamp::Now();
+  geckoEvent.mRefPoint = aPosition;
+  geckoEvent.buttons = 0;
+  return geckoEvent;
+}
+
+bool
+SwipeTracker::SendSwipeEvent(EventMessage aMsg, uint32_t aDirection, double aDelta)
+{
+  WidgetSimpleGestureEvent geckoEvent =
+    CreateSwipeGestureEvent(aMsg, &mWidget, mEventPosition);
+  geckoEvent.mDirection = aDirection;
+  geckoEvent.mDelta = aDelta;
+  geckoEvent.mAllowedDirections = mAllowedDirections;
+  return mWidget.DispatchWindowEvent(geckoEvent);
+}
+
+} // namespace mozilla