diff -r 000000000000 -r 6474c204b198 gfx/layers/apz/src/Axis.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/layers/apz/src/Axis.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,296 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 ts=8 et tw=80 : */
+/* 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 "Axis.h"
+#include <math.h>                       // for fabsf, pow, powf
+#include <algorithm>                    // for max
+#include "AsyncPanZoomController.h"     // for AsyncPanZoomController
+#include "mozilla/layers/APZCTreeManager.h" // for APZCTreeManager
+#include "FrameMetrics.h"               // for FrameMetrics
+#include "mozilla/Attributes.h"         // for MOZ_FINAL
+#include "mozilla/Preferences.h"        // for Preferences
+#include "mozilla/gfx/Rect.h"           // for RoundedIn
+#include "mozilla/mozalloc.h"           // for operator new
+#include "nsMathUtils.h"                // for NS_lround
+#include "nsThreadUtils.h"              // for NS_DispatchToMainThread, etc
+#include "nscore.h"                     // for NS_IMETHOD
+#include "gfxPrefs.h"                   // for the preferences
+
+namespace mozilla {
+namespace layers {
+
+Axis::Axis(AsyncPanZoomController* aAsyncPanZoomController)
+  : mPos(0),
+    mVelocity(0.0f),
+    mAxisLocked(false),
+    mAsyncPanZoomController(aAsyncPanZoomController)
+{
+}
+
+void Axis::UpdateWithTouchAtDevicePoint(int32_t aPos, const TimeDuration& aTimeDelta) {
+  float newVelocity = mAxisLocked ? 0 : (mPos - aPos) / aTimeDelta.ToMilliseconds();
+  if (gfxPrefs::APZMaxVelocity() > 0.0f) {
+    newVelocity = std::min(newVelocity, gfxPrefs::APZMaxVelocity() * APZCTreeManager::GetDPI());
+  }
+
+  mVelocity = newVelocity;
+  mPos = aPos;
+
+  // Limit queue size pased on pref
+  mVelocityQueue.AppendElement(mVelocity);
+  if (mVelocityQueue.Length() > gfxPrefs::APZMaxVelocityQueueSize()) {
+    mVelocityQueue.RemoveElementAt(0);
+  }
+}
+
+void Axis::StartTouch(int32_t aPos) {
+  mStartPos = aPos;
+  mPos = aPos;
+  mAxisLocked = false;
+}
+
+float Axis::AdjustDisplacement(float aDisplacement, float& aOverscrollAmountOut) {
+  if (mAxisLocked) {
+    aOverscrollAmountOut = 0;
+    return 0;
+  }
+
+  float displacement = aDisplacement;
+
+  // 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;
+    aOverscrollAmountOut = DisplacementWillOverscrollAmount(displacement);
+    displacement -= aOverscrollAmountOut;
+  }
+  return displacement;
+}
+
+float Axis::PanDistance() {
+  return fabsf(mPos - mStartPos);
+}
+
+float Axis::PanDistance(float aPos) {
+  return fabsf(aPos - mStartPos);
+}
+
+void Axis::EndTouch() {
+  // Calculate the mean velocity and empty the queue.
+  int count = mVelocityQueue.Length();
+  if (count) {
+    mVelocity = 0;
+    while (!mVelocityQueue.IsEmpty()) {
+      mVelocity += mVelocityQueue[0];
+      mVelocityQueue.RemoveElementAt(0);
+    }
+    mVelocity /= count;
+  }
+}
+
+void Axis::CancelTouch() {
+  mVelocity = 0.0f;
+  while (!mVelocityQueue.IsEmpty()) {
+    mVelocityQueue.RemoveElementAt(0);
+  }
+}
+
+bool Axis::Scrollable() {
+    if (mAxisLocked) {
+        return false;
+    }
+    return GetCompositionLength() < GetPageLength();
+}
+
+bool Axis::FlingApplyFrictionOrCancel(const TimeDuration& aDelta) {
+  if (fabsf(mVelocity) <= gfxPrefs::APZFlingStoppedThreshold()) {
+    // If the velocity is very low, just set it to 0 and stop the fling,
+    // otherwise we'll just asymptotically approach 0 and the user won't
+    // actually see any changes.
+    mVelocity = 0.0f;
+    return false;
+  } else {
+    mVelocity *= pow(1.0f - gfxPrefs::APZFlingFriction(), float(aDelta.ToMilliseconds()));
+  }
+  return true;
+}
+
+Axis::Overscroll Axis::GetOverscroll() {
+  // If the current pan takes the window to the left of or above the current
+  // page rect.
+  bool minus = GetOrigin() < GetPageStart();
+  // If the current pan takes the window to the right of or below the current
+  // page rect.
+  bool plus = GetCompositionEnd() > GetPageEnd();
+  if (minus && plus) {
+    return OVERSCROLL_BOTH;
+  }
+  if (minus) {
+    return OVERSCROLL_MINUS;
+  }
+  if (plus) {
+    return OVERSCROLL_PLUS;
+  }
+  return OVERSCROLL_NONE;
+}
+
+float Axis::GetExcess() {
+  switch (GetOverscroll()) {
+  case OVERSCROLL_MINUS: return GetOrigin() - GetPageStart();
+  case OVERSCROLL_PLUS: return GetCompositionEnd() - GetPageEnd();
+  case OVERSCROLL_BOTH: return (GetCompositionEnd() - GetPageEnd()) +
+                               (GetPageStart() - GetOrigin());
+  default: return 0;
+  }
+}
+
+Axis::Overscroll Axis::DisplacementWillOverscroll(float aDisplacement) {
+  // If the current pan plus a displacement takes the window to the left of or
+  // above the current page rect.
+  bool minus = GetOrigin() + aDisplacement < GetPageStart();
+  // If the current pan plus a displacement takes the window to the right of or
+  // below the current page rect.
+  bool plus = GetCompositionEnd() + aDisplacement > GetPageEnd();
+  if (minus && plus) {
+    return OVERSCROLL_BOTH;
+  }
+  if (minus) {
+    return OVERSCROLL_MINUS;
+  }
+  if (plus) {
+    return OVERSCROLL_PLUS;
+  }
+  return OVERSCROLL_NONE;
+}
+
+float Axis::DisplacementWillOverscrollAmount(float aDisplacement) {
+  switch (DisplacementWillOverscroll(aDisplacement)) {
+  case OVERSCROLL_MINUS: return (GetOrigin() + aDisplacement) - GetPageStart();
+  case OVERSCROLL_PLUS: return (GetCompositionEnd() + aDisplacement) - GetPageEnd();
+  // Don't handle overscrolled in both directions; a displacement can't cause
+  // this, it must have already been zoomed out too far.
+  default: return 0;
+  }
+}
+
+float Axis::ScaleWillOverscrollAmount(float aScale, float aFocus) {
+  float originAfterScale = (GetOrigin() + aFocus) - (aFocus / aScale);
+
+  bool both = ScaleWillOverscrollBothSides(aScale);
+  bool minus = originAfterScale < GetPageStart();
+  bool plus = (originAfterScale + (GetCompositionLength() / aScale)) > GetPageEnd();
+
+  if ((minus && plus) || both) {
+    // If we ever reach here it's a bug in the client code.
+    MOZ_ASSERT(false, "In an OVERSCROLL_BOTH condition in ScaleWillOverscrollAmount");
+    return 0;
+  }
+  if (minus) {
+    return originAfterScale - GetPageStart();
+  }
+  if (plus) {
+    return originAfterScale + (GetCompositionLength() / aScale) - GetPageEnd();
+  }
+  return 0;
+}
+
+float Axis::GetVelocity() {
+  return mAxisLocked ? 0 : mVelocity;
+}
+
+void Axis::SetVelocity(float aVelocity) {
+  mVelocity = aVelocity;
+}
+
+float Axis::GetCompositionEnd() const {
+  return GetOrigin() + GetCompositionLength();
+}
+
+float Axis::GetPageEnd() const {
+  return GetPageStart() + GetPageLength();
+}
+
+float Axis::GetOrigin() const {
+  CSSPoint origin = mAsyncPanZoomController->GetFrameMetrics().GetScrollOffset();
+  return GetPointOffset(origin);
+}
+
+float Axis::GetCompositionLength() const {
+  const FrameMetrics& metrics = mAsyncPanZoomController->GetFrameMetrics();
+  return GetRectLength(metrics.CalculateCompositedRectInCssPixels());
+}
+
+float Axis::GetPageStart() const {
+  CSSRect pageRect = mAsyncPanZoomController->GetFrameMetrics().mScrollableRect;
+  return GetRectOffset(pageRect);
+}
+
+float Axis::GetPageLength() const {
+  CSSRect pageRect = mAsyncPanZoomController->GetFrameMetrics().mScrollableRect;
+  return GetRectLength(pageRect);
+}
+
+bool Axis::ScaleWillOverscrollBothSides(float aScale) {
+  const FrameMetrics& metrics = mAsyncPanZoomController->GetFrameMetrics();
+
+  CSSToParentLayerScale scale(metrics.GetZoomToParent().scale * aScale);
+  CSSRect cssCompositionBounds = metrics.mCompositionBounds / scale;
+
+  return GetRectLength(metrics.mScrollableRect) < GetRectLength(cssCompositionBounds);
+}
+
+bool Axis::HasRoomToPan() const {
+  return GetOrigin() > GetPageStart()
+      || GetCompositionEnd() < GetPageEnd();
+}
+
+
+AxisX::AxisX(AsyncPanZoomController* aAsyncPanZoomController)
+  : Axis(aAsyncPanZoomController)
+{
+
+}
+
+float AxisX::GetPointOffset(const CSSPoint& aPoint) const
+{
+  return aPoint.x;
+}
+
+float AxisX::GetRectLength(const CSSRect& aRect) const
+{
+  return aRect.width;
+}
+
+float AxisX::GetRectOffset(const CSSRect& aRect) const
+{
+  return aRect.x;
+}
+
+AxisY::AxisY(AsyncPanZoomController* aAsyncPanZoomController)
+  : Axis(aAsyncPanZoomController)
+{
+
+}
+
+float AxisY::GetPointOffset(const CSSPoint& aPoint) const
+{
+  return aPoint.y;
+}
+
+float AxisY::GetRectLength(const CSSRect& aRect) const
+{
+  return aRect.height;
+}
+
+float AxisY::GetRectOffset(const CSSRect& aRect) const
+{
+  return aRect.y;
+}
+
+}
+}