Bug 892684 - Implement axis locking in AsyncPanZoomController [r=kats,botond]

browser/metro/profile/metro.js

@@ -42,6 +42,9 @@ pref("gfx.azpc.fling_repaint_interval", "50"); // prefer 20 fps
 pref("gfx.axis.fling_friction", "0.002");
 pref("gfx.axis.fling_stopped_threshold", "0.2");
 
+// 0 = free, 1 = standard, 2 = sticky
+pref("apzc.axis_lock_mode", 1);
+
 // Enable Microsoft TSF support by default for imes.
 pref("intl.enable_tsf_support", true);
 

gfx/layers/ipc/AsyncPanZoomController.cpp

@@ -21,6 +21,7 @@
 #include "gfxTypes.h"                   // for gfxFloat
 #include "mozilla/Assertions.h"         // for MOZ_ASSERT, etc
 #include "mozilla/ClearOnShutdown.h"    // for ClearOnShutdown
+#include "mozilla/Constants.h"          // for M_PI
 #include "mozilla/EventForwards.h"      // for nsEventStatus_*
 #include "mozilla/Preferences.h"        // for Preferences
 #include "mozilla/ReentrantMonitor.h"   // for ReentrantMonitorAutoEnter, etc
@@ -64,7 +65,27 @@ namespace layers {
  */
 static float gTouchStartTolerance = 1.0f/16.0f;
 
-static const float EPSILON = 0.0001;
+static const float EPSILON = 0.0001f;
+
+/**
+ * Angle from axis within which we stay axis-locked
+ */
+static const double AXIS_LOCK_ANGLE = M_PI / 6.0; // 30 degrees
+
+/**
+ * The distance in inches the user must pan before axis lock can be broken
+ */
+static const float AXIS_BREAKOUT_THRESHOLD = 1.0f/32.0f;
+
+/**
+ * The angle at which axis lock can be broken
+ */
+static const double AXIS_BREAKOUT_ANGLE = M_PI / 8.0; // 22.5 degrees
+
+/**
+ * The preferred axis locking style. See AxisLockMode for possible values.
+ */
+static int32_t gAxisLockMode = 0;
 
 /**
  * Maximum amount of time while panning before sending a viewport change. This
@@ -153,6 +174,23 @@ static int gAsyncScrollTimeout = 300;
  */
 static bool gAsyncZoomDisabled = false;
 
+/**
+ * Is aAngle within the given threshold of the horizontal axis?
+ * @param aAngle an angle in radians in the range [0, pi]
+ * @param aThreshold an angle in radians in the range [0, pi/2]
+ */
+static bool IsCloseToHorizontal(float aAngle, float aThreshold)
+{
+  return (aAngle < aThreshold || aAngle > (M_PI - aThreshold));
+}
+
+// As above, but for the vertical axis.
+static bool IsCloseToVertical(float aAngle, float aThreshold)
+{
+  return (fabs(aAngle - (M_PI / 2)) < aThreshold);
+}
+
+
 static TimeStamp sFrameTime;
 
 static TimeStamp
@@ -191,6 +229,7 @@ AsyncPanZoomController::InitializeGlobalState()
   Preferences::AddIntVarCache(&gAsyncScrollThrottleTime, "apzc.asyncscroll.throttle", gAsyncScrollThrottleTime);
   Preferences::AddIntVarCache(&gAsyncScrollTimeout, "apzc.asyncscroll.timeout", gAsyncScrollTimeout);
   Preferences::AddBoolVarCache(&gAsyncZoomDisabled, "apzc.asynczoom.disabled", gAsyncZoomDisabled);
+  Preferences::AddIntVarCache(&gAxisLockMode, "apzc.axis_lock_mode", gAxisLockMode);
 
   gComputedTimingFunction = new ComputedTimingFunction();
   gComputedTimingFunction->Init(
@@ -272,6 +311,11 @@ AsyncPanZoomController::GetTouchStartTolerance()
   return gTouchStartTolerance;
 }
 
+/* static */AsyncPanZoomController::AxisLockMode AsyncPanZoomController::GetAxisLockMode()
+{
+  return static_cast<AxisLockMode>(gAxisLockMode);
+}
+
 static CSSPoint
 WidgetSpaceToCompensatedViewportSpace(const ScreenPoint& aPoint,
                                       const CSSToScreenScale& aCurrentZoom)
@@ -295,7 +339,7 @@ nsEventStatus AsyncPanZoomController::ReceiveInputEvent(const InputData& aEvent)
   // responding in a timely fashion, this only introduces a nearly constant few
   // hundred ms of lag.
   if (mFrameMetrics.mMayHaveTouchListeners && aEvent.mInputType == MULTITOUCH_INPUT &&
-      (mState == NOTHING || mState == TOUCHING || mState == PANNING)) {
+      (mState == NOTHING || mState == TOUCHING || IsPanningState(mState))) {
     const MultiTouchInput& multiTouchInput = aEvent.AsMultiTouchInput();
     if (multiTouchInput.mType == MultiTouchInput::MULTITOUCH_START) {
       SetState(WAITING_LISTENERS);
@@ -413,6 +457,8 @@ nsEventStatus AsyncPanZoomController::OnTouchStart(const MultiTouchInput& aEvent
       break;
     case TOUCHING:
     case PANNING:
+    case PANNING_LOCKED_X:
+    case PANNING_LOCKED_Y:
     case PINCHING:
     case WAITING_LISTENERS:
       NS_WARNING("Received impossible touch in OnTouchStart");
@@ -452,6 +498,8 @@ nsEventStatus AsyncPanZoomController::OnTouchMove(const MultiTouchInput& aEvent)
     }
 
     case PANNING:
+    case PANNING_LOCKED_X:
+    case PANNING_LOCKED_Y:
       TrackTouch(aEvent);
       return nsEventStatus_eConsumeNoDefault;
 
@@ -495,6 +543,8 @@ nsEventStatus AsyncPanZoomController::OnTouchEnd(const MultiTouchInput& aEvent)
     return nsEventStatus_eIgnore;
 
   case PANNING:
+  case PANNING_LOCKED_X:
+  case PANNING_LOCKED_Y:
     {
       ReentrantMonitorAutoEnter lock(mMonitor);
       ScheduleComposite();
@@ -704,13 +754,37 @@ const gfx::Point AsyncPanZoomController::GetAccelerationVector() {
 }
 
 void AsyncPanZoomController::StartPanning(const MultiTouchInput& aEvent) {
-  float dx = mX.PanDistance(),
+  ReentrantMonitorAutoEnter lock(mMonitor);
-        dy = mY.PanDistance();
+
+  ScreenIntPoint point = GetFirstTouchScreenPoint(aEvent);
+  float dx = mX.PanDistance(point.x);
+  float dy = mY.PanDistance(point.y);
+
+  // When the touch move breaks through the pan threshold, reposition the touch down origin
+  // so the page won't jump when we start panning.
+  mX.StartTouch(point.x);
+  mY.StartTouch(point.y);
+  mLastEventTime = aEvent.mTime;
+
+  if (GetAxisLockMode() == FREE) {
+    SetState(PANNING);
+    return;
+  }
 
   double angle = atan2(dy, dx); // range [-pi, pi]
   angle = fabs(angle); // range [0, pi]
 
-  SetState(PANNING);
+  if (!mX.Scrollable() || !mY.Scrollable()) {
+    SetState(PANNING);
+  } else if (IsCloseToHorizontal(angle, AXIS_LOCK_ANGLE)) {
+    mY.SetScrollingDisabled(true);
+    SetState(PANNING_LOCKED_X);
+  } else if (IsCloseToVertical(angle, AXIS_LOCK_ANGLE)) {
+    mX.SetScrollingDisabled(true);
+    SetState(PANNING_LOCKED_Y);
+  } else {
+    SetState(PANNING);
+  }
 }
 
 void AsyncPanZoomController::UpdateWithTouchAtDevicePoint(const MultiTouchInput& aEvent) {
@@ -775,6 +849,32 @@ void AsyncPanZoomController::TrackTouch(const MultiTouchInput& aEvent) {
     return;
   }
 
+  // If we're axis-locked, check if the user is trying to break the lock
+  if (GetAxisLockMode() == STICKY) {
+    ScreenIntPoint point = GetFirstTouchScreenPoint(aEvent);
+    float dx = mX.PanDistance(point.x);
+    float dy = mY.PanDistance(point.y);
+
+    double angle = atan2(dy, dx); // range [-pi, pi]
+    angle = fabs(angle); // range [0, pi]
+
+    float breakThreshold = AXIS_BREAKOUT_THRESHOLD * APZCTreeManager::GetDPI();
+
+    if (fabs(dx) > breakThreshold || fabs(dy) > breakThreshold) {
+      if (mState == PANNING_LOCKED_X) {
+        if (!IsCloseToHorizontal(angle, AXIS_BREAKOUT_ANGLE)) {
+          mY.SetScrollingDisabled(false);
+          SetState(PANNING);
+        }
+      } else if (mState == PANNING_LOCKED_Y) {
+        if (!IsCloseToVertical(angle, AXIS_BREAKOUT_ANGLE)) {
+          mX.SetScrollingDisabled(false);
+          SetState(PANNING);
+        }
+      }
+    }
+  }
+
   UpdateWithTouchAtDevicePoint(aEvent);
 
   AttemptScroll(prevTouchPoint, touchPoint);
@@ -1361,14 +1461,18 @@ void AsyncPanZoomController::SetState(PanZoomState aNewState) {
   }
 
   if (mGeckoContentController) {
-    if (oldState == PANNING && aNewState != PANNING) {
+    if (IsPanningState(oldState) && !IsPanningState(aNewState)) {
       mGeckoContentController->HandlePanEnd();
-    } else if (oldState != PANNING && aNewState == PANNING) {
+    } else if (!IsPanningState(oldState) && IsPanningState(aNewState)) {
       mGeckoContentController->HandlePanBegin();
     }
   }
 }
 
+bool AsyncPanZoomController::IsPanningState(PanZoomState aState) {
+  return (aState == PANNING || aState == PANNING_LOCKED_X || aState == PANNING_LOCKED_Y);
+}
+
 void AsyncPanZoomController::TimeoutTouchListeners() {
   mTouchListenerTimeoutTask = nullptr;
   ContentReceivedTouch(false);

gfx/layers/ipc/AsyncPanZoomController.h

@@ -484,7 +484,11 @@ private:
     NOTHING,        /* no touch-start events received */
     FLING,          /* all touches removed, but we're still scrolling page */
     TOUCHING,       /* one touch-start event received */
-    PANNING,        /* panning the frame */
+
+    PANNING,           /* panning the frame */
+    PANNING_LOCKED_X,  /* touch-start followed by move (i.e. panning with axis lock) X axis */
+    PANNING_LOCKED_Y,  /* as above for Y axis */
+
     PINCHING,       /* nth touch-start, where n > 1. this mode allows pan and zoom */
     ANIMATING_ZOOM, /* animated zoom to a new rect */
     WAITING_LISTENERS, /* a state halfway between NOTHING and TOUCHING - the user has
@@ -492,6 +496,14 @@ private:
                     prevented the default actions yet. we still need to abort animations. */
   };
 
+  enum AxisLockMode {
+    FREE,     /* No locking at all */
+    STANDARD, /* Default axis locking mode that remains locked until pan ends*/
+    STICKY,   /* Allow lock to be broken, with hysteresis */
+  };
+
+  static AxisLockMode GetAxisLockMode();
+
   /**
    * Helper to set the current state. Holds the monitor before actually setting
    * it. If the monitor is already held by the current thread, it is safe to
@@ -499,6 +511,8 @@ private:
    */
   void SetState(PanZoomState aState);
 
+  bool IsPanningState(PanZoomState mState);
+
   uint64_t mLayersId;
   nsRefPtr<CompositorParent> mCompositorParent;
   TaskThrottler mPaintThrottler;

gfx/layers/ipc/Axis.cpp

@@ -1,5 +1,5 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set sw=4 ts=8 et tw=80 : */
+/* 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/. */
@@ -103,13 +103,14 @@ Axis::Axis(AsyncPanZoomController* aAsyncPanZoomController)
   : mPos(0),
     mVelocity(0.0f),
     mAcceleration(0),
+    mScrollingDisabled(false),
     mAsyncPanZoomController(aAsyncPanZoomController)
 {
   InitAxisPrefs();
 }
 
 void Axis::UpdateWithTouchAtDevicePoint(int32_t aPos, const TimeDuration& aTimeDelta) {
-  float newVelocity = (mPos - aPos) / aTimeDelta.ToMilliseconds();
+  float newVelocity = mScrollingDisabled ? 0 : (mPos - aPos) / aTimeDelta.ToMilliseconds();
 
   bool curVelocityBelowThreshold = fabsf(newVelocity) < gVelocityThreshold;
   bool directionChange = (mVelocity > 0) != (newVelocity > 0);
@@ -133,9 +134,15 @@ void Axis::UpdateWithTouchAtDevicePoint(int32_t aPos, const TimeDuration& aTimeD
 void Axis::StartTouch(int32_t aPos) {
   mStartPos = aPos;
   mPos = aPos;
+  mScrollingDisabled = false;
 }
 
 float Axis::AdjustDisplacement(float aDisplacement, float& aOverscrollAmountOut) {
+  if (mScrollingDisabled) {
+    aOverscrollAmountOut = 0;
+    return 0;
+  }
+
   if (fabsf(mVelocity) < gVelocityThreshold) {
     mAcceleration = 0;
   }
@@ -159,6 +166,10 @@ float Axis::PanDistance() {
   return fabsf(mPos - mStartPos);
 }
 
+float Axis::PanDistance(float aPos) {
+  return fabsf(aPos - mStartPos);
+}
+
 void Axis::EndTouch() {
   mAcceleration++;
 
@@ -182,6 +193,13 @@ void Axis::CancelTouch() {
   }
 }
 
+bool Axis::Scrollable() {
+    if (mScrollingDisabled) {
+        return false;
+    }
+    return GetCompositionLength() < GetPageLength();
+}
+
 bool Axis::FlingApplyFrictionOrCancel(const TimeDuration& aDelta) {
   if (fabsf(mVelocity) <= gFlingStoppedThreshold) {
     // If the velocity is very low, just set it to 0 and stop the fling,
@@ -284,7 +302,7 @@ float Axis::ScaleWillOverscrollAmount(ScreenToScreenScale aScale, float aFocus)
 }
 
 float Axis::GetVelocity() {
-  return mVelocity;
+  return mScrollingDisabled ? 0 : mVelocity;
 }
 
 float Axis::GetAccelerationFactor() {

gfx/layers/ipc/Axis.h

@@ -1,5 +1,5 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set sw=4 ts=8 et tw=80 : */
+/* 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/. */
@@ -69,10 +69,11 @@ public:
 
   /**
    * Takes a requested displacement to the position of this axis, and adjusts
-   * it to account for acceleration  (which might increase the displacement)
+   * it to account for acceleration (which might increase the displacement),
-   * and overscroll (which might decrease the displacement; this is to prevent
+   * overscroll (which might decrease the displacement; this is to prevent the
-   * the viewport from overscrolling the page rect). If overscroll ocurred,
+   * viewport from overscrolling the page rect), and axis locking (which might
-   * its amount is written to |aOverscrollAmountOut|.
+   * prevent any displacement from happening). If overscroll ocurred, its amount
+   * is written to |aOverscrollAmountOut|.
    * The adjusted displacement is returned.
    */
   float AdjustDisplacement(float aDisplacement, float& aOverscrollAmountOut);
@@ -84,6 +85,12 @@ public:
    */
   float PanDistance();
 
+  /**
+   * Gets the distance between the starting position of the touch supplied in
+   * startTouch() and the supplied position.
+   */
+  float PanDistance(float aPos);
+
   /**
    * Applies friction during a fling, or cancels the fling if the velocity is
    * too low. Returns true if the fling should continue to another frame, or
@@ -92,6 +99,14 @@ public:
    */
   bool FlingApplyFrictionOrCancel(const TimeDuration& aDelta);
 
+  /*
+   * Returns true if the page is zoomed in to some degree along this axis such that scrolling is
+   * possible and this axis has not been scroll locked while panning. Otherwise, returns false.
+   */
+  bool Scrollable();
+
+  void SetScrollingDisabled(bool aDisabled) { mScrollingDisabled = aDisabled; }
+
   /**
    * Gets the overscroll state of the axis in its current position.
    */
@@ -184,6 +199,7 @@ protected:
   // 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 mScrollingDisabled;     // Whether movement on this axis is locked.
   AsyncPanZoomController* mAsyncPanZoomController;
   nsTArray<float> mVelocityQueue;
 };

modules/libpref/src/init/all.js

@@ -273,6 +273,12 @@ pref("media.video_stats.enabled", true);
 // Whether to enable the audio writing APIs on the audio element
 pref("media.audio_data.enabled", true);
 
+// Whether to lock touch scrolling to one axis at a time
+// 0 = FREE (No locking at all)
+// 1 = STANDARD (Once locked, remain locked until scrolling ends)
+// 2 = STICKY (Allow lock to be broken, with hysteresis)
+pref("apzc.axis_lock_mode", 0);
+
 #ifdef XP_MACOSX
 // Whether to run in native HiDPI mode on machines with "Retina"/HiDPI display;
 //   <= 0 : hidpi mode disabled, display will just use pixel-based upscaling