Bug 1034376 - Avoid APZC being stuck in overscrolled state when CancelAnimation() is called during panning. r=kats

--HG--
extra : rebase_source : bbc3a02d6be7081be77b58cb2795aa57ce794002

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -412,34 +412,13 @@ GetFrameTime() {
   return sFrameTime;
 }
 
-// This is a base class for animations that can deal with
-// overscroll states. In particular, it ensures that overscroll
-// states are cleared when the animation is cancelled.
-class OverscrollableAnimation: public AsyncPanZoomAnimation {
-public:
-  OverscrollableAnimation(AsyncPanZoomController& aApzc,
-                          const TimeDuration& aRepaintInterval = TimeDuration::Forever())
-    : AsyncPanZoomAnimation(aRepaintInterval)
-    , mApzc(aApzc)
-  {
-  }
-
-  virtual void Cancel() MOZ_OVERRIDE
-  {
-    mApzc.mX.ClearOverscroll();
-    mApzc.mY.ClearOverscroll();
-  }
-
-protected:
-  AsyncPanZoomController& mApzc;
-};
-
-class FlingAnimation: public OverscrollableAnimation {
+class FlingAnimation: public AsyncPanZoomAnimation {
 public:
   FlingAnimation(AsyncPanZoomController& aApzc,
                  bool aApplyAcceleration,
                  bool aAllowOverscroll)
-    : OverscrollableAnimation(aApzc, TimeDuration::FromMilliseconds(gfxPrefs::APZFlingRepaintInterval()))
+    : AsyncPanZoomAnimation(TimeDuration::FromMilliseconds(gfxPrefs::APZFlingRepaintInterval()))
+    , mApzc(aApzc)
     , mAllowOverscroll(aAllowOverscroll)
   {
     TimeStamp now = GetFrameTime();
@@ -594,6 +573,7 @@ private:
          + (aSupplemental * gfxPrefs::APZFlingAccelSupplementalMultiplier());
   }
 
+  AsyncPanZoomController& mApzc;
   bool mAllowOverscroll;
 };
 
@@ -656,10 +636,10 @@ private:
   CSSToScreenScale mEndZoom;
 };
 
-class OverscrollSnapBackAnimation: public OverscrollableAnimation {
+class OverscrollSnapBackAnimation: public AsyncPanZoomAnimation {
 public:
   OverscrollSnapBackAnimation(AsyncPanZoomController& aApzc)
-    : OverscrollableAnimation(aApzc)
+    : mApzc(aApzc)
   {
   }
 
@@ -671,6 +651,8 @@ public:
     bool continueY = mApzc.mY.SampleSnapBack(aDelta);
     return continueX || continueY;
   }
+private:
+  AsyncPanZoomController& mApzc;
 };
 
 void
@@ -1771,10 +1753,13 @@ void AsyncPanZoomController::CancelAnimation() {
   ReentrantMonitorAutoEnter lock(mMonitor);
   APZC_LOG("%p running CancelAnimation in state %d\n", this, mState);
   SetState(NOTHING);
-  if (mAnimation) {
-    mAnimation->Cancel();
-    mAnimation = nullptr;
-    // mAnimation->Cancel() may have done something that requires a repaint.
+  mAnimation = nullptr;
+  // Setting the state to nothing and cancelling the animation can
+  // preempt normal mechanisms for relieving overscroll, so we need to clear
+  // overscroll here.
+  if (mX.IsOverscrolled() || mY.IsOverscrolled()) {
+    mX.ClearOverscroll();
+    mY.ClearOverscroll();
     RequestContentRepaint();
     ScheduleComposite();
     UpdateSharedCompositorFrameMetrics();

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -800,7 +800,6 @@ public:
   bool TakeOverFling(ScreenPoint aVelocity);
 
 private:
-  friend class OverscrollableAnimation;
   friend class FlingAnimation;
   friend class OverscrollSnapBackAnimation;
   // The initial velocity of the most recent fling.
@@ -1039,9 +1038,6 @@ public:
   virtual bool Sample(FrameMetrics& aFrameMetrics,
                       const TimeDuration& aDelta) = 0;
 
-  // Called if the animation is cancelled before it ends.
-  virtual void Cancel() {}
-
   /**
    * Get the deferred tasks in |mDeferredTasks|. See |mDeferredTasks|
    * for more information.

gfx/tests/gtest/TestAsyncPanZoomController.cpp

@@ -212,7 +212,8 @@ void ApzcPan(AsyncPanZoomController* apzc,
              int aTouchEndY,
              bool expectIgnoredPan = false,
              bool hasTouchListeners = false,
-             nsTArray<uint32_t>* aAllowedTouchBehaviors = nullptr) {
+             nsTArray<uint32_t>* aAllowedTouchBehaviors = nullptr,
+             bool aKeepFingerDown = false) {
 
   const int TIME_BETWEEN_TOUCH_EVENT = 100;
   const int OVERCOME_TOUCH_TOLERANCE = 100;
@@ -272,11 +273,13 @@ void ApzcPan(AsyncPanZoomController* apzc,
   status = apzc->ReceiveInputEvent(mti);
   EXPECT_EQ(touchMoveStatus, status);
 
-  mti =
-    MultiTouchInput(MultiTouchInput::MULTITOUCH_END, aTime, TimeStamp(), 0);
-  aTime += TIME_BETWEEN_TOUCH_EVENT;
-  mti.mTouches.AppendElement(SingleTouchData(0, ScreenIntPoint(10, aTouchEndY), ScreenSize(0, 0), 0, 0));
-  status = apzc->ReceiveInputEvent(mti);
+  if (!aKeepFingerDown) {
+    mti =
+      MultiTouchInput(MultiTouchInput::MULTITOUCH_END, aTime, TimeStamp(), 0);
+    aTime += TIME_BETWEEN_TOUCH_EVENT;
+    mti.mTouches.AppendElement(SingleTouchData(0, ScreenIntPoint(10, aTouchEndY), ScreenSize(0, 0), 0, 0));
+    status = apzc->ReceiveInputEvent(mti);
+  }
 
   // Since we've explicitly built the overscroll handoff chain before
   // touch-start, we need to explicitly clear it after touch-end.
@@ -966,6 +969,36 @@ TEST_F(AsyncPanZoomControllerTester, OverScrollAbort) {
   apzc->Destroy();
 }
 
+TEST_F(AsyncPanZoomControllerTester, OverScrollPanningAbort) {
+  TestScopedBoolPref overscrollEnabledPref("apz.overscroll.enabled", true);
+
+  nsRefPtr<MockContentController> mcc = new NiceMock<MockContentController>();
+  nsRefPtr<TestAPZCTreeManager> tm = new TestAPZCTreeManager();
+  nsRefPtr<TestAsyncPanZoomController> apzc = new TestAsyncPanZoomController(0, mcc, tm);
+
+  apzc->SetFrameMetrics(TestFrameMetrics());
+  apzc->NotifyLayersUpdated(TestFrameMetrics(), true);
+
+  // Pan sufficiently to hit overscroll behaviour. Keep the finger down so
+  // the pan does not end.
+  int time = 0;
+  int touchStart = 500;
+  int touchEnd = 10;
+  ApzcPan(apzc, tm, time, touchStart, touchEnd,
+          false, false, nullptr,   // filling it defaults, wish we had named arguments
+          true);                   // keep finger down
+  EXPECT_TRUE(apzc->IsOverscrolled());
+
+  // Check that calling CancelAnimation() while the user is still panning
+  // (and thus no fling or snap-back animation has had a chance to start)
+  // clears the overscroll.
+  apzc->CancelAnimation();
+  EXPECT_FALSE(apzc->IsOverscrolled());
+  apzc->AssertStateIsReset();
+
+  apzc->Destroy();
+}
+
 TEST_F(AsyncPanZoomControllerTester, ShortPress) {
   nsRefPtr<MockContentControllerDelayed> mcc = new NiceMock<MockContentControllerDelayed>();
   nsRefPtr<TestAPZCTreeManager> tm = new TestAPZCTreeManager();