Bug 968112: Remove acceleration code from APZC r=kats

dom/ipc/TabChild.cpp

@@ -610,7 +610,7 @@ TabChild::HandlePossibleViewportChange()
     // The page must have been refreshed in some way such as a new document or
     // new CSS viewport, so we know that there's no velocity, acceleration, and
     // we have no idea how long painting will take.
-    metrics, ScreenPoint(0.0f, 0.0f), gfx::Point(0.0f, 0.0f), 0.0);
+    metrics, ScreenPoint(0.0f, 0.0f), 0.0);
   metrics.mCumulativeResolution = metrics.mZoom / metrics.mDevPixelsPerCSSPixel * ScreenToLayerScale(1);
   // This is the root layer, so the cumulative resolution is the same
   // as the resolution.

gfx/layers/ipc/AsyncPanZoomController.cpp

@@ -994,10 +994,6 @@ const ScreenPoint AsyncPanZoomController::GetVelocityVector() {
   return ScreenPoint(mX.GetVelocity(), mY.GetVelocity());
 }
 
-const gfx::Point AsyncPanZoomController::GetAccelerationVector() {
-  return gfx::Point(mX.GetAccelerationFactor(), mY.GetAccelerationFactor());
-}
-
 void AsyncPanZoomController::HandlePanningWithTouchAction(double aAngle, TouchBehaviorFlags aBehavior) {
   // Handling of cross sliding will need to be added in this method after touch-action released
   // enabled by default.
@@ -1309,7 +1305,6 @@ EnlargeDisplayPortAlongAxis(float* aOutOffset, float* aOutLength,
 const CSSRect AsyncPanZoomController::CalculatePendingDisplayPort(
   const FrameMetrics& aFrameMetrics,
   const ScreenPoint& aVelocity,
-  const gfx::Point& aAcceleration,
   double aEstimatedPaintDuration)
 {
   // convert to milliseconds
@@ -1343,10 +1338,9 @@ const CSSRect AsyncPanZoomController::CalculatePendingDisplayPort(
   displayPort = displayPort.ForceInside(scrollableRect) - scrollOffset;
 
   APZC_LOG_FM(aFrameMetrics,
-    "Calculated displayport as (%f %f %f %f) from velocity (%f %f) acceleration (%f %f) paint time %f metrics",
+    "Calculated displayport as (%f %f %f %f) from velocity (%f %f) paint time %f metrics",
     displayPort.x, displayPort.y, displayPort.width, displayPort.height,
-    aVelocity.x, aVelocity.y, aAcceleration.x, aAcceleration.y,
-    (float)estimatedPaintDurationMillis);
+    aVelocity.x, aVelocity.y, (float)estimatedPaintDurationMillis);
 
   return displayPort;
 }
@@ -1365,7 +1359,6 @@ void AsyncPanZoomController::RequestContentRepaint(FrameMetrics& aFrameMetrics)
   aFrameMetrics.mDisplayPort =
     CalculatePendingDisplayPort(aFrameMetrics,
                                 GetVelocityVector(),
-                                GetAccelerationVector(),
                                 mPaintThrottler.AverageDuration().ToSeconds());
 
   // If we're trying to paint what we already think is painted, discard this
@@ -1720,7 +1713,6 @@ void AsyncPanZoomController::ZoomToRect(CSSRect aRect) {
     endZoomToMetrics.mDisplayPort =
       CalculatePendingDisplayPort(endZoomToMetrics,
                                   ScreenPoint(0,0),
-                                  gfx::Point(0,0),
                                   0);
 
     StartAnimation(new ZoomAnimation(

gfx/layers/ipc/AsyncPanZoomController.h

@@ -240,7 +240,6 @@ public:
   static const CSSRect CalculatePendingDisplayPort(
     const FrameMetrics& aFrameMetrics,
     const ScreenPoint& aVelocity,
-    const gfx::Point& aAcceleration,
     double aEstimatedPaintDuration);
 
   /**
@@ -438,11 +437,6 @@ protected:
    */
   const ScreenPoint GetVelocityVector();
 
-  /**
-   * Gets a vector of the acceleration factors of each axis.
-   */
-  const gfx::Point GetAccelerationVector();
-
   /**
    * Gets a reference to the first touch point from a MultiTouchInput.  This
    * gets only the first one and assumes the rest are either missing or not

gfx/layers/ipc/Axis.cpp

@@ -33,22 +33,6 @@ static float gMaxEventAcceleration = 999.0f;
  */
 static float gFlingFriction = 0.002f;
 
-/**
- * Threshold for velocity beneath which we turn off any acceleration we had
- * during repeated flings.
- */
-static float gVelocityThreshold = 0.14f;
-
-/**
- * Amount of acceleration we multiply in each time the user flings in one
- * direction. Every time they let go of the screen, we increase the acceleration
- * by this amount raised to the power of the amount of times they have let go,
- * times two (to make the curve steeper).  This stops if the user lets go and we
- * slow down enough, or if they put their finger down without moving it for a
- * moment (or in the opposite direction).
- */
-static float gAccelerationMultiplier = 1.125f;
-
 /**
  * When flinging, if the velocity goes below this number, we just stop the
  * animation completely. This is to prevent asymptotically approaching 0
@@ -67,8 +51,6 @@ static void ReadAxisPrefs()
 {
   Preferences::AddFloatVarCache(&gMaxEventAcceleration, "apz.max_event_acceleration", gMaxEventAcceleration);
   Preferences::AddFloatVarCache(&gFlingFriction, "apz.fling_friction", gFlingFriction);
-  Preferences::AddFloatVarCache(&gVelocityThreshold, "apz.velocity_threshold", gVelocityThreshold);
-  Preferences::AddFloatVarCache(&gAccelerationMultiplier, "apz.acceleration_multiplier", gAccelerationMultiplier);
   Preferences::AddFloatVarCache(&gFlingStoppedThreshold, "apz.fling_stopped_threshold", gFlingStoppedThreshold);
   Preferences::AddUintVarCache(&gMaxVelocityQueueSize, "apz.max_velocity_queue_size", gMaxVelocityQueueSize);
 }
@@ -100,7 +82,6 @@ static void InitAxisPrefs()
 Axis::Axis(AsyncPanZoomController* aAsyncPanZoomController)
   : mPos(0),
     mVelocity(0.0f),
-    mAcceleration(0),
     mAxisLocked(false),
     mAsyncPanZoomController(aAsyncPanZoomController)
 {
@@ -110,15 +91,6 @@ Axis::Axis(AsyncPanZoomController* aAsyncPanZoomController)
 void Axis::UpdateWithTouchAtDevicePoint(int32_t aPos, const TimeDuration& aTimeDelta) {
   float newVelocity = mAxisLocked ? 0 : (mPos - aPos) / aTimeDelta.ToMilliseconds();
 
-  bool curVelocityBelowThreshold = fabsf(newVelocity) < gVelocityThreshold;
-  bool directionChange = (mVelocity > 0) != (newVelocity > 0);
-
-  // If we've changed directions, or the current velocity threshold, stop any
-  // acceleration we've accumulated.
-  if (directionChange || curVelocityBelowThreshold) {
-    mAcceleration = 0;
-  }
-
   mVelocity = newVelocity;
   mPos = aPos;
 
@@ -145,23 +117,17 @@ float Axis::AdjustDisplacement(float aDisplacement, float& aOverscrollAmountOut,
   if (aScrollingDisabled) {
     // Scrolling is disabled on this axis, stop scrolling.
     aOverscrollAmountOut = aDisplacement;
-    mAcceleration = 0;
     return 0;
   }
 
-  if (fabsf(mVelocity) < gVelocityThreshold) {
-    mAcceleration = 0;
-  }
+  float displacement = aDisplacement;
 
-  float accelerationFactor = GetAccelerationFactor();
-  float displacement = aDisplacement * accelerationFactor;
   // If this displacement will cause an overscroll, throttle it. Can potentially
   // bring it to 0 even if the velocity is high.
   if (DisplacementWillOverscroll(displacement) != OVERSCROLL_NONE) {
     // No need to have a velocity along this axis anymore; it won't take us
     // anywhere, so we're just spinning needlessly.
     mVelocity = 0.0f;
-    mAcceleration = 0;
     aOverscrollAmountOut = DisplacementWillOverscrollAmount(displacement);
     displacement -= aOverscrollAmountOut;
   }
@@ -177,8 +143,6 @@ float Axis::PanDistance(float aPos) {
 }
 
 void Axis::EndTouch() {
-  mAcceleration++;
-
   // Calculate the mean velocity and empty the queue.
   int count = mVelocityQueue.Length();
   if (count) {
@@ -193,7 +157,6 @@ void Axis::EndTouch() {
 
 void Axis::CancelTouch() {
   mVelocity = 0.0f;
-  mAcceleration = 0;
   while (!mVelocityQueue.IsEmpty()) {
     mVelocityQueue.RemoveElementAt(0);
   }
@@ -302,10 +265,6 @@ float Axis::GetVelocity() {
   return mAxisLocked ? 0 : mVelocity;
 }
 
-float Axis::GetAccelerationFactor() {
-  return powf(gAccelerationMultiplier, std::max(0, (mAcceleration - 4) * 3));
-}
-
 float Axis::GetCompositionEnd() {
   return GetOrigin() + GetCompositionLength();
 }

gfx/layers/ipc/Axis.h

@@ -70,12 +70,11 @@ public:
   void CancelTouch();
 
   /**
-   * Takes a requested displacement to the position of this axis, and adjusts
-   * it to account for acceleration (which might increase the displacement),
-   * overscroll (which might decrease the displacement; this is to prevent the
-   * viewport from overscrolling the page rect), and axis locking (which might
-   * prevent any displacement from happening). If overscroll ocurred, its amount
-   * is written to |aOverscrollAmountOut|.
+   * Takes a requested displacement to the position of this axis, and adjusts it
+   * to account for overscroll (which might decrease the displacement; this is
+   * to prevent the viewport from overscrolling the page rect), and axis locking
+   * (which might prevent any displacement from happening). If overscroll
+   * ocurred, its amount is written to |aOverscrollAmountOut|.
    * The adjusted displacement is returned.
    *
    * aScrollingDisabled is used to indicate that no scrolling should happen
@@ -128,12 +127,6 @@ public:
    */
   float GetExcess();
 
-  /**
-   * Gets the factor of acceleration applied to the velocity, based on the
-   * amount of flings that have been done successively.
-   */
-  float GetAccelerationFactor();
-
   /**
    * Gets the raw velocity of this axis at this moment.
    */
@@ -188,12 +181,6 @@ protected:
   int32_t mPos;
   int32_t mStartPos;
   float mVelocity;
-  // Acceleration is represented by an int, which is the power we raise a
-  // constant to and then multiply the velocity by whenever it is sampled. We do
-  // this only when we detect that the user wants to do a fast fling; that is,
-  // they are flinging multiple times in a row very quickly, probably trying to
-  // reach one of the extremes of the page.
-  int32_t mAcceleration;
   bool mAxisLocked;     // Whether movement on this axis is locked.
   AsyncPanZoomController* mAsyncPanZoomController;
   nsTArray<float> mVelocityQueue;