Bug 1934164. Remove unused scroll grab code. r=botond

Differential Revision: https://phabricator.services.mozilla.com/D230635

Author: tnikkel

dom/base/nsContentUtils.cpp

@@ -6948,13 +6948,6 @@ void* nsContentUtils::AllocClassMatchingInfo(nsINode* aRootNode,
   return info;
 }
 
-bool nsContentUtils::HasScrollgrab(nsIContent* aContent) {
-  // If we ever standardize this feature we'll want to hook this up properly
-  // again. For now we're removing all the DOM-side code related to it but
-  // leaving the layout and APZ handling for it in place.
-  return false;
-}
-
 void nsContentUtils::FlushLayoutForTree(nsPIDOMWindowOuter* aWindow) {
   if (!aWindow) {
     return;

dom/base/nsContentUtils.h

@@ -2532,12 +2532,6 @@ class nsContentUtils {
   static void GetAltText(nsAString& text);
   static void GetModifierSeparatorText(nsAString& text);
 
-  /**
-   * Returns if aContent has the 'scrollgrab' property.
-   * aContent may be null (in this case false is returned).
-   */
-  static bool HasScrollgrab(nsIContent* aContent);
-
   /**
    * Flushes the layout tree (recursively)
    *

gfx/layers/FrameMetrics.cpp

@@ -267,9 +267,6 @@ std::ostream& operator<<(std::ostream& aStream,
   if (aMetadata.GetScrollParentId() != ScrollableLayerGuid::NULL_SCROLL_ID) {
     aStream << "] [scrollParent=" << aMetadata.GetScrollParentId();
   }
-  if (aMetadata.GetHasScrollgrab()) {
-    aStream << "] [scrollgrab";
-  }
   aStream << "] [overscroll=" << aMetadata.GetOverscrollBehavior() << "] ["
           << aMetadata.GetScrollUpdates().Length() << " scrollupdates"
           << "] }";

gfx/layers/FrameMetrics.h

@@ -752,7 +752,6 @@ struct ScrollMetadata {
         mPageScrollAmount(0, 0),
         mInteractiveWidget(
             dom::InteractiveWidgetUtils::DefaultInteractiveWidgetMode()),
-        mHasScrollgrab(false),
         mIsLayersIdRoot(false),
         mIsAutoDirRootContentRTL(false),
         mForceDisableApz(false),
@@ -771,7 +770,6 @@ struct ScrollMetadata {
            mLineScrollAmount == aOther.mLineScrollAmount &&
            mPageScrollAmount == aOther.mPageScrollAmount &&
            mInteractiveWidget == aOther.mInteractiveWidget &&
-           mHasScrollgrab == aOther.mHasScrollgrab &&
            mIsLayersIdRoot == aOther.mIsLayersIdRoot &&
            mIsAutoDirRootContentRTL == aOther.mIsAutoDirRootContentRTL &&
            mForceDisableApz == aOther.mForceDisableApz &&
@@ -827,10 +825,6 @@ struct ScrollMetadata {
   void SetPageScrollAmount(const LayoutDeviceIntSize& size) {
     mPageScrollAmount = size;
   }
-  void SetHasScrollgrab(bool aHasScrollgrab) {
-    mHasScrollgrab = aHasScrollgrab;
-  }
-  bool GetHasScrollgrab() const { return mHasScrollgrab; }
   void SetIsLayersIdRoot(bool aValue) { mIsLayersIdRoot = aValue; }
   bool IsLayersIdRoot() const { return mIsLayersIdRoot; }
   void SetIsAutoDirRootContentRTL(bool aValue) {
@@ -957,9 +951,6 @@ struct ScrollMetadata {
   // be checked on AsyncPanZoomController::mScrollMetadata.
   dom::InteractiveWidget mInteractiveWidget;
 
-  // Whether or not this frame is for an element marked 'scrollgrab'.
-  bool mHasScrollgrab : 1;
-
   // Whether these framemetrics are for the root scroll frame (root element if
   // we don't have a root scroll frame) for its layers id.
   bool mIsLayersIdRoot : 1;

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -3076,11 +3076,6 @@ APZCTreeManager::BuildOverscrollHandoffChain(
     apzc = scrollParent.get();
   }
 
-  // Now adjust the chain to account for scroll grabbing. Sorting is a bit
-  // of an overkill here, but scroll grabbing will likely be generalized
-  // to scroll priorities, so we might as well do it this way.
-  result->SortByScrollPriority();
-
   // Print the overscroll chain for debugging.
   for (uint32_t i = 0; i < result->Length(); ++i) {
     APZCTM_LOG("OverscrollHandoffChain[%d] = %p\n", i,

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -5671,7 +5671,6 @@ void AsyncPanZoomController::NotifyLayersUpdated(
     Metrics().SetCumulativeResolution(aLayerMetrics.GetCumulativeResolution());
     Metrics().SetTransformToAncestorScale(
         aLayerMetrics.GetTransformToAncestorScale());
-    mScrollMetadata.SetHasScrollgrab(aScrollMetadata.GetHasScrollgrab());
     mScrollMetadata.SetLineScrollAmount(aScrollMetadata.GetLineScrollAmount());
     mScrollMetadata.SetPageScrollAmount(aScrollMetadata.GetPageScrollAmount());
     mScrollMetadata.SetSnapInfo(ScrollSnapInfo(aScrollMetadata.GetSnapInfo()));

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -447,12 +447,6 @@ class AsyncPanZoomController {
   void ClearOverscroll();
   void ClearPhysicalOverscroll();
 
-  /**
-   * Returns whether this APZC is for an element marked with the 'scrollgrab'
-   * attribute.
-   */
-  bool HasScrollgrab() const { return mScrollMetadata.GetHasScrollgrab(); }
-
   /**
    * Returns whether this APZC has scroll snap points.
    */

gfx/layers/apz/src/OverscrollHandoffState.cpp

@@ -20,22 +20,6 @@ void OverscrollHandoffChain::Add(AsyncPanZoomController* aApzc) {
   mChain.push_back(aApzc);
 }
 
-struct CompareByScrollPriority {
-  bool operator()(const RefPtr<AsyncPanZoomController>& a,
-                  const RefPtr<AsyncPanZoomController>& b) const {
-    return a->HasScrollgrab() && !b->HasScrollgrab();
-  }
-};
-
-void OverscrollHandoffChain::SortByScrollPriority() {
-  // The sorting being stable ensures that the relative order between
-  // non-scrollgrabbing APZCs remains child -> parent.
-  // (The relative order between scrollgrabbing APZCs will also remain
-  // child -> parent, though that's just an artefact of the implementation
-  // and users of 'scrollgrab' should not rely on this.)
-  std::stable_sort(mChain.begin(), mChain.end(), CompareByScrollPriority());
-}
-
 const RefPtr<AsyncPanZoomController>& OverscrollHandoffChain::GetApzcAtIndex(
     uint32_t aIndex) const {
   MOZ_ASSERT(aIndex < Length());

gfx/layers/apz/src/OverscrollHandoffState.h

@@ -26,8 +26,7 @@ class AsyncPanZoomController;
  * This class represents the chain of APZCs along which overscroll is handed
  * off. It is created by APZCTreeManager by starting from an initial APZC which
  * is the target for input events, and following the scroll parent ID links
- * (often but not always corresponding to parent pointers in the APZC tree),
- * then adjusting for scrollgrab.
+ * (often but not always corresponding to parent pointers in the APZC tree).
  */
 class OverscrollHandoffChain {
  protected:

gfx/layers/apz/test/gtest/TestScrollHandoff.cpp

@@ -142,67 +142,6 @@ class APZScrollHandoffTester : public APZCTreeManagerTester {
     rootApzc = ApzcOf(root);
   }
 
-  void CreateScrollgrabLayerTree(bool makeParentScrollable = true) {
-    const char* treeShape = "x(x)";
-    LayerIntRect layerVisibleRect[] = {
-        LayerIntRect(0, 0, 100, 100),  // scroll-grabbing parent
-        LayerIntRect(0, 20, 100, 80)   // child
-    };
-    CreateScrollData(treeShape, layerVisibleRect);
-    float parentHeight = makeParentScrollable ? 120 : 100;
-    SetScrollableFrameMetrics(root, ScrollableLayerGuid::START_SCROLL_ID,
-                              CSSRect(0, 0, 100, parentHeight));
-    SetScrollableFrameMetrics(layers[1],
-                              ScrollableLayerGuid::START_SCROLL_ID + 1,
-                              CSSRect(0, 0, 100, 800));
-    SetScrollHandoff(layers[1], root);
-    registration = MakeUnique<ScopedLayerTreeRegistration>(LayersId{0}, mcc);
-    UpdateHitTestingTree();
-    rootApzc = ApzcOf(root);
-    rootApzc->GetScrollMetadata().SetHasScrollgrab(true);
-  }
-
-  void TestFlingAcceleration() {
-    // Jack up the fling acceleration multiplier so we can easily determine
-    // whether acceleration occured.
-    const float kAcceleration = 100.0f;
-    SCOPED_GFX_PREF_FLOAT("apz.fling_accel_base_mult", kAcceleration);
-    SCOPED_GFX_PREF_FLOAT("apz.fling_accel_min_fling_velocity", 0.0);
-    SCOPED_GFX_PREF_FLOAT("apz.fling_accel_min_pan_velocity", 0.0);
-
-    RefPtr<TestAsyncPanZoomController> childApzc = ApzcOf(layers[1]);
-
-    // Pan once, enough to fully scroll the scrollgrab parent and then scroll
-    // and fling the child.
-    QueueMockHitResult(ScrollableLayerGuid::START_SCROLL_ID + 1);
-    Pan(manager, 70, 40);
-
-    // Give the fling animation a chance to start.
-    SampleAnimationsOnce();
-
-    float childVelocityAfterFling1 = childApzc->GetVelocityVector().y;
-
-    // Pan again.
-    QueueMockHitResult(ScrollableLayerGuid::START_SCROLL_ID + 1);
-    Pan(manager, 70, 40);
-
-    // Give the fling animation a chance to start.
-    // This time it should be accelerated.
-    SampleAnimationsOnce();
-
-    float childVelocityAfterFling2 = childApzc->GetVelocityVector().y;
-
-    // We should have accelerated once.
-    // The division by 2 is to account for friction.
-    EXPECT_GT(childVelocityAfterFling2,
-              childVelocityAfterFling1 * kAcceleration / 2);
-
-    // We should not have accelerated twice.
-    // The division by 4 is to account for friction.
-    EXPECT_LE(childVelocityAfterFling2,
-              childVelocityAfterFling1 * kAcceleration * kAcceleration / 4);
-  }
-
   void TestCrossApzcAxisLock() {
     SCOPED_GFX_PREF_INT("apz.axis_lock.mode", 1);
 
@@ -567,62 +506,6 @@ TEST_F(APZScrollHandoffTester, SimultaneousFlings) {
   parent2->AssertStateIsFling();
 }
 
-#ifndef MOZ_WIDGET_ANDROID  // Currently fails on Android
-TEST_F(APZScrollHandoffTester, Scrollgrab) {
-  SCOPED_GFX_PREF_BOOL("apz.allow_immediate_handoff", true);
-
-  // Set up the layer tree
-  CreateScrollgrabLayerTree();
-
-  RefPtr<TestAsyncPanZoomController> childApzc = ApzcOf(layers[1]);
-
-  // Pan on the child, enough to fully scroll the scrollgrab parent (20 px)
-  // and leave some more (another 15 px) for the child.
-  Pan(childApzc, 80, 45);
-
-  // Check that the parent and child have scrolled as much as we expect.
-  EXPECT_EQ(20, rootApzc->GetFrameMetrics().GetVisualScrollOffset().y);
-  EXPECT_EQ(15, childApzc->GetFrameMetrics().GetVisualScrollOffset().y);
-}
-#endif
-
-TEST_F(APZScrollHandoffTester, ScrollgrabFling) {
-  SCOPED_GFX_PREF_BOOL("apz.allow_immediate_handoff", true);
-  SCOPED_GFX_PREF_FLOAT("apz.fling_min_velocity_threshold", 0.0f);
-
-  // Set up the layer tree
-  CreateScrollgrabLayerTree();
-
-  RefPtr<TestAsyncPanZoomController> childApzc = ApzcOf(layers[1]);
-
-  // Pan on the child, not enough to fully scroll the scrollgrab parent.
-  Pan(childApzc, 80, 70);
-
-  // Check that it is the scrollgrab parent that's in a fling, not the child.
-  rootApzc->AssertStateIsFling();
-  childApzc->AssertStateIsReset();
-}
-
-TEST_F(APZScrollHandoffTesterMock, ScrollgrabFlingAcceleration1) {
-  SCOPED_GFX_PREF_BOOL("apz.allow_immediate_handoff", true);
-  SCOPED_GFX_PREF_FLOAT("apz.fling_min_velocity_threshold", 0.0f);
-  CreateScrollgrabLayerTree(true /* make parent scrollable */);
-
-  // Note: Usually, fling acceleration does not work across handoff, because our
-  // fling acceleration code does not propagate the "fling cancel velocity"
-  // across handoff. However, this test sets apz.fling_min_velocity_threshold to
-  // zero, so the "fling cancel velocity" is allowed to be zero, and fling
-  // acceleration succeeds, almost by accident.
-  TestFlingAcceleration();
-}
-
-TEST_F(APZScrollHandoffTesterMock, ScrollgrabFlingAcceleration2) {
-  SCOPED_GFX_PREF_BOOL("apz.allow_immediate_handoff", true);
-  SCOPED_GFX_PREF_FLOAT("apz.fling_min_velocity_threshold", 0.0f);
-  CreateScrollgrabLayerTree(false /* do not make parent scrollable */);
-  TestFlingAcceleration();
-}
-
 TEST_F(APZScrollHandoffTester, ImmediateHandoffDisallowed_Pan) {
   SCOPED_GFX_PREF_BOOL("apz.allow_immediate_handoff", false);
 

gfx/layers/ipc/LayersMessageUtils.h

@@ -599,7 +599,6 @@ struct ParamTraits<mozilla::layers::ScrollMetadata>
     WriteParam(aWriter, aParam.mLineScrollAmount);
     WriteParam(aWriter, aParam.mPageScrollAmount);
     WriteParam(aWriter, aParam.mInteractiveWidget);
-    WriteParam(aWriter, aParam.mHasScrollgrab);
     WriteParam(aWriter, aParam.mIsLayersIdRoot);
     WriteParam(aWriter, aParam.mIsAutoDirRootContentRTL);
     WriteParam(aWriter, aParam.mForceDisableApz);
@@ -634,8 +633,6 @@ struct ParamTraits<mozilla::layers::ScrollMetadata>
             ReadParam(aReader, &aResult->mLineScrollAmount) &&
             ReadParam(aReader, &aResult->mPageScrollAmount) &&
             ReadParam(aReader, &aResult->mInteractiveWidget) &&
-            ReadBoolForBitfield(aReader, aResult,
-                                &paramType::SetHasScrollgrab) &&
             ReadBoolForBitfield(aReader, aResult,
                                 &paramType::SetIsLayersIdRoot) &&
             ReadBoolForBitfield(aReader, aResult,

layout/base/nsLayoutUtils.cpp

@@ -8931,14 +8931,6 @@ ScrollMetadata nsLayoutUtils::ComputeScrollMetadata(
 
   metrics.SetPresShellId(presShell->GetPresShellId());
 
-  // If the scroll frame's content is marked 'scrollgrab', record this
-  // in the FrameMetrics so APZ knows to provide the scroll grabbing
-  // behaviour.
-  if (aScrollFrame &&
-      nsContentUtils::HasScrollgrab(aScrollFrame->GetContent())) {
-    metadata.SetHasScrollgrab(true);
-  }
-
   if (ShouldDisableApzForElement(aContent)) {
     metadata.SetForceDisableApz(true);
   }

layout/generic/ScrollContainerFrame.cpp

@@ -4205,7 +4205,7 @@ void ScrollContainerFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
   // minimal display port.
   if (aBuilder->IsPaintingToWindow()) {
     if (DisplayPortUtils::HasNonMinimalDisplayPort(GetContent()) ||
-        mZoomableByAPZ || nsContentUtils::HasScrollgrab(GetContent())) {
+        mZoomableByAPZ) {
       aBuilder->SetContainsNonMinimalDisplayPort();
     }
   }
@@ -4537,9 +4537,7 @@ bool ScrollContainerFrame::DecideScrollableLayer(
   // the compositor can find the scrollable layer for async scrolling.
   // If the element is marked 'scrollgrab', also force building of a layer
   // so that APZ can implement scroll grabbing.
-  mWillBuildScrollableLayer = hasDisplayPort ||
-                              nsContentUtils::HasScrollgrab(content) ||
-                              mZoomableByAPZ;
+  mWillBuildScrollableLayer = hasDisplayPort || mZoomableByAPZ;
   return mWillBuildScrollableLayer;
 }
 
@@ -5994,8 +5992,7 @@ bool ScrollContainerFrame::IsScrollingActive() const {
 
   nsIContent* content = GetContent();
   return mHasBeenScrolledRecently || IsAlwaysActive() ||
-         DisplayPortUtils::HasDisplayPort(content) ||
-         nsContentUtils::HasScrollgrab(content);
+         DisplayPortUtils::HasDisplayPort(content);
 }
 
 void ScrollContainerFrame::FinishReflowForScrollbar(