Bug 1042103 - Allow overscroll to be retained between input blocks. r=botond

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -1497,7 +1497,7 @@ APZCTreeManager::GetScreenToApzcTransform(const AsyncPanZoomController *aApzc) c
     // ancestorUntransform is updated to RC.Inverse() * QC.Inverse() when parent == P
     ancestorUntransform = parent->GetAncestorTransform().Inverse();
     // asyncUntransform is updated to PA.Inverse() when parent == P
-    Matrix4x4 asyncUntransform = Matrix4x4(parent->GetCurrentAsyncTransform()).Inverse();
+    Matrix4x4 asyncUntransform = parent->GetCurrentAsyncTransformWithOverscroll().Inverse();
     // untransformSinceLastApzc is RC.Inverse() * QC.Inverse() * PA.Inverse()
     Matrix4x4 untransformSinceLastApzc = ancestorUntransform * asyncUntransform;
 
@@ -1529,7 +1529,7 @@ APZCTreeManager::GetApzcToGeckoTransform(const AsyncPanZoomController *aApzc) co
   // leftmost matrix in a multiplication is applied first.
 
   // asyncUntransform is LA.Inverse()
-  Matrix4x4 asyncUntransform = Matrix4x4(aApzc->GetCurrentAsyncTransform()).Inverse();
+  Matrix4x4 asyncUntransform = aApzc->GetCurrentAsyncTransformWithOverscroll().Inverse();
 
   // aTransformToGeckoOut is initialized to LA.Inverse() * LD * MC * NC * OC * PC
   result = asyncUntransform * aApzc->GetTransformToLastDispatchedPaint() * aApzc->GetAncestorTransform();

gfx/layers/apz/src/APZUtils.h

@@ -16,6 +16,11 @@ enum HitTestResult {
   HitDispatchToContentRegion,
 };
 
+enum CancelAnimationFlags : uint32_t {
+  Default = 0,            /* Cancel all animations */
+  ExcludeOverscroll = 1   /* Don't clear overscroll */
+};
+
 }
 }
 

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -1147,7 +1147,7 @@ nsEventStatus AsyncPanZoomController::OnTouchStart(const MultiTouchInput& aEvent
     case ANIMATING_ZOOM:
     case SMOOTH_SCROLL:
     case OVERSCROLL_ANIMATION:
-      CurrentTouchBlock()->GetOverscrollHandoffChain()->CancelAnimations();
+      CurrentTouchBlock()->GetOverscrollHandoffChain()->CancelAnimations(ExcludeOverscroll);
       // Fall through.
     case NOTHING: {
       mX.StartTouch(point.x, aEvent.mTime);
@@ -1270,7 +1270,11 @@ nsEventStatus AsyncPanZoomController::OnTouchEnd(const MultiTouchInput& aEvent)
     // that were not big enough to trigger scrolling. Clear that out.
     mX.SetVelocity(0);
     mY.SetVelocity(0);
-    SetState(NOTHING);
+    // It's possible we may be overscrolled if the user tapped during a
+    // previous overscroll pan. Make sure to snap back in this situation.
+    if (!SnapBackIfOverscrolled()) {
+      SetState(NOTHING);
+    }
     return nsEventStatus_eIgnore;
 
   case PANNING:
@@ -2165,7 +2169,7 @@ void AsyncPanZoomController::StartAnimation(AsyncPanZoomAnimation* aAnimation)
   ScheduleComposite();
 }
 
-void AsyncPanZoomController::CancelAnimation() {
+void AsyncPanZoomController::CancelAnimation(CancelAnimationFlags aFlags) {
   ReentrantMonitorAutoEnter lock(mMonitor);
   APZC_LOG("%p running CancelAnimation in state %d\n", this, mState);
   SetState(NOTHING);
@@ -2177,7 +2181,7 @@ void AsyncPanZoomController::CancelAnimation() {
   // 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()) {
+  if (!(aFlags & ExcludeOverscroll) && IsOverscrolled()) {
     ClearOverscroll();
     RequestContentRepaint();
     ScheduleComposite();
@@ -2654,6 +2658,10 @@ ViewTransform AsyncPanZoomController::GetCurrentAsyncTransform() const {
   return ViewTransform(mFrameMetrics.GetAsyncZoom(), -translation);
 }
 
+Matrix4x4 AsyncPanZoomController::GetCurrentAsyncTransformWithOverscroll() const {
+  return Matrix4x4(GetCurrentAsyncTransform()) * GetOverscrollTransform();
+}
+
 Matrix4x4 AsyncPanZoomController::GetTransformToLastDispatchedPaint() const {
   ReentrantMonitorAutoEnter lock(mMonitor);
 

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -20,6 +20,7 @@
 #include "InputData.h"
 #include "Axis.h"
 #include "InputQueue.h"
+#include "APZUtils.h"
 #include "LayersTypes.h"
 #include "TaskThrottler.h"
 #include "mozilla/gfx/Matrix.h"
@@ -217,6 +218,12 @@ public:
    */
   ViewTransform GetCurrentAsyncTransform() const;
 
+  /**
+   * Returns the same transform as GetCurrentAsyncTransform(), but includes
+   * any transform due to axis over-scroll.
+   */
+  Matrix4x4 GetCurrentAsyncTransformWithOverscroll() const;
+
   /**
    * Returns the transform to take something from the coordinate space of the
    * last thing we know gecko painted, to the coordinate space of the last thing
@@ -285,8 +292,10 @@ public:
 
   /**
    * Cancels any currently running animation.
+   * aFlags is a bit-field to provide specifics of how to cancel the animation.
+   * See CancelAnimationFlags.
    */
-  void CancelAnimation();
+  void CancelAnimation(CancelAnimationFlags aFlags = Default);
 
   /**
    * Clear any overscroll on this APZC.

gfx/layers/apz/src/Axis.cpp

@@ -126,6 +126,8 @@ bool Axis::AdjustDisplacement(ParentLayerCoord aDisplacement,
     return false;
   }
 
+  StopSamplingOverscrollAnimation();
+
   ParentLayerCoord displacement = aDisplacement;
 
   // First consume any overscroll in the opposite direction along this axis.
@@ -160,12 +162,13 @@ ParentLayerCoord Axis::ApplyResistance(ParentLayerCoord aRequestedOverscroll) co
   // The actual overscroll is the requested overscroll multiplied by this
   // factor; this should prevent overscrolling by more than the composition
   // length.
-  float resistanceFactor = 1 - fabsf(mOverscroll) / GetCompositionLength();
+  float resistanceFactor = 1 - fabsf(GetOverscroll()) / GetCompositionLength();
   return resistanceFactor < 0 ? ParentLayerCoord(0) : aRequestedOverscroll * resistanceFactor;
 }
 
 void Axis::OverscrollBy(ParentLayerCoord aOverscroll) {
   MOZ_ASSERT(CanScroll());
+  StopSamplingOverscrollAnimation();
   aOverscroll = ApplyResistance(aOverscroll);
   if (aOverscroll > 0) {
 #ifdef DEBUG
@@ -200,6 +203,12 @@ ParentLayerCoord Axis::GetOverscroll() const {
   return result;
 }
 
+void Axis::StopSamplingOverscrollAnimation() {
+  ParentLayerCoord overscroll = GetOverscroll();
+  ClearOverscroll();
+  mOverscroll = overscroll;
+}
+
 void Axis::StepOverscrollAnimation(double aStepDurationMilliseconds) {
   // Apply spring physics to the overscroll as time goes on.
   // Note: this method of sampling isn't perfectly smooth, as it assumes

gfx/layers/apz/src/Axis.h

@@ -251,6 +251,10 @@ protected:
   // actual overscroll amount.
   ParentLayerCoord ApplyResistance(ParentLayerCoord aOverscroll) const;
 
+  // Helper function to disable overscroll transformations triggered by
+  // SampleOverscrollAnimation().
+  void StopSamplingOverscrollAnimation();
+
   // Helper function for SampleOverscrollAnimation().
   void StepOverscrollAnimation(double aStepDurationMilliseconds);
 

gfx/layers/apz/src/HitTestingTreeNode.cpp

@@ -174,7 +174,7 @@ HitTestingTreeNode::Untransform(const ParentLayerPoint& aPoint) const
   // convert into Layer coordinate space
   gfx::Matrix4x4 localTransform = mTransform;
   if (mApzc) {
-    localTransform = localTransform * gfx::Matrix4x4(mApzc->GetCurrentAsyncTransform());
+    localTransform = localTransform * mApzc->GetCurrentAsyncTransformWithOverscroll();
   }
   gfx::Point4D point = localTransform.Inverse().ProjectPoint(aPoint.ToUnknownPoint());
   return point.HasPositiveWCoord()

gfx/layers/apz/src/InputQueue.cpp

@@ -186,7 +186,7 @@ InputQueue::CancelAnimationsForNewBlock(CancelableBlockState* aBlock)
         INPQ_LOG("block %p tagged as fast-motion\n", touch);
       }
     }
-    aBlock->GetOverscrollHandoffChain()->CancelAnimations();
+    aBlock->GetOverscrollHandoffChain()->CancelAnimations(ExcludeOverscroll);
   }
 }
 

gfx/layers/apz/src/OverscrollHandoffState.cpp

@@ -88,9 +88,12 @@ OverscrollHandoffChain::FlushRepaints() const
 }
 
 void
-OverscrollHandoffChain::CancelAnimations() const
+OverscrollHandoffChain::CancelAnimations(CancelAnimationFlags aFlags) const
 {
-  ForEachApzc(&AsyncPanZoomController::CancelAnimation);
+  MOZ_ASSERT(Length() > 0);
+  for (uint32_t i = 0; i < Length(); ++i) {
+    mChain[i]->CancelAnimation(aFlags);
+  }
 }
 
 void

gfx/layers/apz/src/OverscrollHandoffState.h

@@ -11,6 +11,7 @@
 #include "nsAutoPtr.h"
 #include "nsISupportsImpl.h"  // for NS_INLINE_DECL_REFCOUNTING
 #include "Units.h"            // for ScreenPoint
+#include "APZUtils.h"         // for CancelAnimationFlags
 
 namespace mozilla {
 namespace layers {
@@ -93,7 +94,7 @@ public:
   void FlushRepaints() const;
 
   // Cancel animations all the way up the chain.
-  void CancelAnimations() const;
+  void CancelAnimations(CancelAnimationFlags aFlags = Default) const;
 
   // Clear overscroll all the way up the chain.
   void ClearOverscroll() const;