1 files changed, 414 insertions, 0 deletions
diff --git a/layout/painting/ActiveLayerTracker.cpp b/layout/painting/ActiveLayerTracker.cpp
new file mode 100644
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--- /dev/null
+++ b/layout/painting/ActiveLayerTracker.cpp
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 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 "ActiveLayerTracker.h"
+
+#include "mozilla/AnimationUtils.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/gfx/gfxVars.h"
+#include "mozilla/gfx/Matrix.h"
+#include "mozilla/EffectSet.h"
+#include "mozilla/MotionPathUtils.h"
+#include "mozilla/PodOperations.h"
+#include "mozilla/StaticPtr.h"
+#include "gfx2DGlue.h"
+#include "nsExpirationTracker.h"
+#include "nsContainerFrame.h"
+#include "nsIContent.h"
+#include "nsRefreshDriver.h"
+#include "nsPIDOMWindow.h"
+#include "mozilla/dom/Document.h"
+#include "nsAnimationManager.h"
+#include "nsStyleTransformMatrix.h"
+#include "nsTransitionManager.h"
+#include "nsDisplayList.h"
+#include "nsDOMCSSDeclaration.h"
+#include "nsLayoutUtils.h"
+
+namespace mozilla {
+
+using namespace gfx;
+
+/**
+ * This tracks the state of a frame that may need active layers due to
+ * ongoing content changes or style changes that indicate animation.
+ *
+ * When no changes of *any* kind are detected after 75-100ms we remove this
+ * object. Because we only track all kinds of activity with a single
+ * nsExpirationTracker, it's possible a frame might remain active somewhat
+ * spuriously if different kinds of changes kept happening, but that almost
+ * certainly doesn't matter.
+ */
+class LayerActivity {
+ public:
+  enum ActivityIndex {
+    ACTIVITY_OPACITY,
+    ACTIVITY_TRANSFORM,
+
+    ACTIVITY_SCALE,
+    ACTIVITY_TRIGGERED_REPAINT,
+
+    // keep as last item
+    ACTIVITY_COUNT
+  };
+
+  explicit LayerActivity(nsIFrame* aFrame) : mFrame(aFrame), mContent(nullptr) {
+    PodArrayZero(mRestyleCounts);
+  }
+  ~LayerActivity();
+  nsExpirationState* GetExpirationState() { return &mState; }
+  uint8_t& RestyleCountForProperty(nsCSSPropertyID aProperty) {
+    return mRestyleCounts[GetActivityIndexForProperty(aProperty)];
+  }
+
+  static ActivityIndex GetActivityIndexForProperty(nsCSSPropertyID aProperty) {
+    switch (aProperty) {
+      case eCSSProperty_opacity:
+        return ACTIVITY_OPACITY;
+      case eCSSProperty_transform:
+      case eCSSProperty_translate:
+      case eCSSProperty_rotate:
+      case eCSSProperty_scale:
+      case eCSSProperty_offset_path:
+      case eCSSProperty_offset_distance:
+      case eCSSProperty_offset_rotate:
+      case eCSSProperty_offset_anchor:
+        // TODO: Bug 1559232: Add offset-position.
+        return ACTIVITY_TRANSFORM;
+      default:
+        MOZ_ASSERT(false);
+        return ACTIVITY_OPACITY;
+    }
+  }
+
+  static ActivityIndex GetActivityIndexForPropertySet(
+      const nsCSSPropertyIDSet& aPropertySet) {
+    if (aPropertySet.IsSubsetOf(
+            nsCSSPropertyIDSet::TransformLikeProperties())) {
+      return ACTIVITY_TRANSFORM;
+    }
+    MOZ_ASSERT(
+        aPropertySet.IsSubsetOf(nsCSSPropertyIDSet::OpacityProperties()));
+    return ACTIVITY_OPACITY;
+  }
+
+  // While tracked, exactly one of mFrame or mContent is non-null, depending
+  // on whether this property is stored on a frame or on a content node.
+  // When this property is expired by the layer activity tracker, both mFrame
+  // and mContent are nulled-out and the property is deleted.
+  nsIFrame* mFrame;
+  nsIContent* mContent;
+
+  nsExpirationState mState;
+
+  // Previous scale due to the CSS transform property.
+  Maybe<MatrixScales> mPreviousTransformScale;
+
+  // Number of restyle operations detected
+  uint8_t mRestyleCounts[ACTIVITY_COUNT];
+};
+
+class LayerActivityTracker final
+    : public nsExpirationTracker<LayerActivity, 4> {
+ public:
+  // 75-100ms is a good timeout period. We use 4 generations of 25ms each.
+  enum { GENERATION_MS = 100 };
+
+  explicit LayerActivityTracker(nsIEventTarget* aEventTarget)
+      : nsExpirationTracker<LayerActivity, 4>(
+            GENERATION_MS, "LayerActivityTracker", aEventTarget) {}
+  ~LayerActivityTracker() override { AgeAllGenerations(); }
+
+  void NotifyExpired(LayerActivity* aObject) override;
+};
+
+static StaticAutoPtr<LayerActivityTracker> gLayerActivityTracker;
+
+LayerActivity::~LayerActivity() {
+  if (mFrame || mContent) {
+    NS_ASSERTION(gLayerActivityTracker, "Should still have a tracker");
+    gLayerActivityTracker->RemoveObject(this);
+  }
+}
+
+// Frames with this property have NS_FRAME_HAS_LAYER_ACTIVITY_PROPERTY set
+NS_DECLARE_FRAME_PROPERTY_DELETABLE(LayerActivityProperty, LayerActivity)
+
+void LayerActivityTracker::NotifyExpired(LayerActivity* aObject) {
+  RemoveObject(aObject);
+
+  nsIFrame* f = aObject->mFrame;
+  nsIContent* c = aObject->mContent;
+  aObject->mFrame = nullptr;
+  aObject->mContent = nullptr;
+
+  MOZ_ASSERT((f == nullptr) != (c == nullptr),
+             "A LayerActivity object should always have a reference to either "
+             "its frame or its content");
+
+  if (f) {
+    f->RemoveStateBits(NS_FRAME_HAS_LAYER_ACTIVITY_PROPERTY);
+    f->RemoveProperty(LayerActivityProperty());
+  } else {
+    c->RemoveProperty(nsGkAtoms::LayerActivity);
+  }
+}
+
+static LayerActivity* GetLayerActivity(nsIFrame* aFrame) {
+  if (!aFrame->HasAnyStateBits(NS_FRAME_HAS_LAYER_ACTIVITY_PROPERTY)) {
+    return nullptr;
+  }
+  return aFrame->GetProperty(LayerActivityProperty());
+}
+
+static LayerActivity* GetLayerActivityForUpdate(nsIFrame* aFrame) {
+  LayerActivity* layerActivity = GetLayerActivity(aFrame);
+  if (layerActivity) {
+    gLayerActivityTracker->MarkUsed(layerActivity);
+  } else {
+    if (!gLayerActivityTracker) {
+      gLayerActivityTracker =
+          new LayerActivityTracker(GetMainThreadSerialEventTarget());
+    }
+    layerActivity = new LayerActivity(aFrame);
+    gLayerActivityTracker->AddObject(layerActivity);
+    aFrame->AddStateBits(NS_FRAME_HAS_LAYER_ACTIVITY_PROPERTY);
+    aFrame->SetProperty(LayerActivityProperty(), layerActivity);
+  }
+  return layerActivity;
+}
+
+static void IncrementMutationCount(uint8_t* aCount) {
+  *aCount = uint8_t(std::min(0xFF, *aCount + 1));
+}
+
+/* static */
+void ActiveLayerTracker::TransferActivityToContent(nsIFrame* aFrame,
+                                                   nsIContent* aContent) {
+  if (!aFrame->HasAnyStateBits(NS_FRAME_HAS_LAYER_ACTIVITY_PROPERTY)) {
+    return;
+  }
+  LayerActivity* layerActivity = aFrame->TakeProperty(LayerActivityProperty());
+  aFrame->RemoveStateBits(NS_FRAME_HAS_LAYER_ACTIVITY_PROPERTY);
+  if (!layerActivity) {
+    return;
+  }
+  layerActivity->mFrame = nullptr;
+  layerActivity->mContent = aContent;
+  aContent->SetProperty(nsGkAtoms::LayerActivity, layerActivity,
+                        nsINode::DeleteProperty<LayerActivity>, true);
+}
+
+/* static */
+void ActiveLayerTracker::TransferActivityToFrame(nsIContent* aContent,
+                                                 nsIFrame* aFrame) {
+  auto* layerActivity = static_cast<LayerActivity*>(
+      aContent->TakeProperty(nsGkAtoms::LayerActivity));
+  if (!layerActivity) {
+    return;
+  }
+  layerActivity->mContent = nullptr;
+  layerActivity->mFrame = aFrame;
+  aFrame->AddStateBits(NS_FRAME_HAS_LAYER_ACTIVITY_PROPERTY);
+  aFrame->SetProperty(LayerActivityProperty(), layerActivity);
+}
+
+static void IncrementScaleRestyleCountIfNeeded(nsIFrame* aFrame,
+                                               LayerActivity* aActivity) {
+  const nsStyleDisplay* display = aFrame->StyleDisplay();
+  if (!display->HasTransformProperty() && !display->HasIndividualTransform() &&
+      display->mOffsetPath.IsNone()) {
+    // The transform was removed.
+    aActivity->mPreviousTransformScale = Nothing();
+    IncrementMutationCount(
+        &aActivity->mRestyleCounts[LayerActivity::ACTIVITY_SCALE]);
+    return;
+  }
+
+  // Compute the new scale due to the CSS transform property.
+  // Note: Motion path doesn't contribute to scale factor. (It only has 2d
+  // translate and 2d rotate, so we use Nothing() for it.)
+  nsStyleTransformMatrix::TransformReferenceBox refBox(aFrame);
+  Matrix4x4 transform = nsStyleTransformMatrix::ReadTransforms(
+      display->mTranslate, display->mRotate, display->mScale, Nothing(),
+      display->mTransform, refBox, AppUnitsPerCSSPixel());
+  Matrix transform2D;
+  if (!transform.Is2D(&transform2D)) {
+    // We don't attempt to handle 3D transforms; just assume the scale changed.
+    aActivity->mPreviousTransformScale = Nothing();
+    IncrementMutationCount(
+        &aActivity->mRestyleCounts[LayerActivity::ACTIVITY_SCALE]);
+    return;
+  }
+
+  MatrixScales scale = transform2D.ScaleFactors();
+  if (aActivity->mPreviousTransformScale == Some(scale)) {
+    return;  // Nothing changed.
+  }
+
+  aActivity->mPreviousTransformScale = Some(scale);
+  IncrementMutationCount(
+      &aActivity->mRestyleCounts[LayerActivity::ACTIVITY_SCALE]);
+}
+
+/* static */
+void ActiveLayerTracker::NotifyRestyle(nsIFrame* aFrame,
+                                       nsCSSPropertyID aProperty) {
+  LayerActivity* layerActivity = GetLayerActivityForUpdate(aFrame);
+  uint8_t& mutationCount = layerActivity->RestyleCountForProperty(aProperty);
+  IncrementMutationCount(&mutationCount);
+
+  if (nsCSSPropertyIDSet::TransformLikeProperties().HasProperty(aProperty)) {
+    IncrementScaleRestyleCountIfNeeded(aFrame, layerActivity);
+  }
+}
+
+static bool IsPresContextInScriptAnimationCallback(
+    nsPresContext* aPresContext) {
+  if (aPresContext->RefreshDriver()->IsInRefresh()) {
+    return true;
+  }
+  // Treat timeouts/setintervals as scripted animation callbacks for our
+  // purposes.
+  nsPIDOMWindowInner* win = aPresContext->Document()->GetInnerWindow();
+  return win && win->IsRunningTimeout();
+}
+
+/* static */
+void ActiveLayerTracker::NotifyInlineStyleRuleModified(
+    nsIFrame* aFrame, nsCSSPropertyID aProperty) {
+  if (IsPresContextInScriptAnimationCallback(aFrame->PresContext())) {
+    LayerActivity* layerActivity = GetLayerActivityForUpdate(aFrame);
+    // We know this is animated, so just hack the mutation count.
+    layerActivity->RestyleCountForProperty(aProperty) = 0xff;
+  }
+}
+
+/* static */
+void ActiveLayerTracker::NotifyNeedsRepaint(nsIFrame* aFrame) {
+  LayerActivity* layerActivity = GetLayerActivityForUpdate(aFrame);
+  if (IsPresContextInScriptAnimationCallback(aFrame->PresContext())) {
+    // This is mirroring NotifyInlineStyleRuleModified's NotifyAnimated logic.
+    // Just max out the restyle count if we're in an animation callback.
+    layerActivity->mRestyleCounts[LayerActivity::ACTIVITY_TRIGGERED_REPAINT] =
+        0xFF;
+  } else {
+    IncrementMutationCount(
+        &layerActivity
+             ->mRestyleCounts[LayerActivity::ACTIVITY_TRIGGERED_REPAINT]);
+  }
+}
+
+static bool IsMotionPathAnimated(nsDisplayListBuilder* aBuilder,
+                                 nsIFrame* aFrame) {
+  return ActiveLayerTracker::IsStyleAnimated(
+             aBuilder, aFrame, nsCSSPropertyIDSet{eCSSProperty_offset_path}) ||
+         (!aFrame->StyleDisplay()->mOffsetPath.IsNone() &&
+          ActiveLayerTracker::IsStyleAnimated(
+              aBuilder, aFrame,
+              nsCSSPropertyIDSet{eCSSProperty_offset_distance,
+                                 eCSSProperty_offset_rotate,
+                                 eCSSProperty_offset_anchor}));
+}
+
+/* static */
+bool ActiveLayerTracker::IsTransformAnimated(nsDisplayListBuilder* aBuilder,
+                                             nsIFrame* aFrame) {
+  return IsStyleAnimated(aBuilder, aFrame,
+                         nsCSSPropertyIDSet::CSSTransformProperties()) ||
+         IsMotionPathAnimated(aBuilder, aFrame);
+}
+
+/* static */
+bool ActiveLayerTracker::IsTransformMaybeAnimated(nsIFrame* aFrame) {
+  return IsStyleAnimated(nullptr, aFrame,
+                         nsCSSPropertyIDSet::CSSTransformProperties()) ||
+         IsMotionPathAnimated(nullptr, aFrame);
+}
+
+/* static */
+bool ActiveLayerTracker::IsStyleAnimated(
+    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
+    const nsCSSPropertyIDSet& aPropertySet) {
+  MOZ_ASSERT(
+      aPropertySet.IsSubsetOf(nsCSSPropertyIDSet::TransformLikeProperties()) ||
+          aPropertySet.IsSubsetOf(nsCSSPropertyIDSet::OpacityProperties()),
+      "Only subset of opacity or transform-like properties set calls this");
+
+  // For display:table content, transforms are applied to the table wrapper
+  // (primary frame) but their will-change style will be specified on the style
+  // frame and, unlike other transform properties, not inherited.
+  // As a result, for transform properties only we need to be careful to look up
+  // the will-change style on the _style_ frame.
+  const nsIFrame* styleFrame = nsLayoutUtils::GetStyleFrame(aFrame);
+  const nsCSSPropertyIDSet transformSet =
+      nsCSSPropertyIDSet::TransformLikeProperties();
+  if ((styleFrame && (styleFrame->StyleDisplay()->mWillChange.bits &
+                      StyleWillChangeBits::TRANSFORM)) &&
+      aPropertySet.Intersects(transformSet) &&
+      (!aBuilder ||
+       aBuilder->IsInWillChangeBudget(aFrame, aFrame->GetSize()))) {
+    return true;
+  }
+  if ((aFrame->StyleDisplay()->mWillChange.bits &
+       StyleWillChangeBits::OPACITY) &&
+      aPropertySet.Intersects(nsCSSPropertyIDSet::OpacityProperties()) &&
+      (!aBuilder ||
+       aBuilder->IsInWillChangeBudget(aFrame, aFrame->GetSize()))) {
+    return !StaticPrefs::gfx_will_change_ignore_opacity();
+  }
+
+  LayerActivity* layerActivity = GetLayerActivity(aFrame);
+  if (layerActivity) {
+    LayerActivity::ActivityIndex activityIndex =
+        LayerActivity::GetActivityIndexForPropertySet(aPropertySet);
+    if (layerActivity->mRestyleCounts[activityIndex] >= 2) {
+      // If the frame needs to be repainted frequently, we probably don't get
+      // much from treating the property as animated, *unless* this frame's
+      // 'scale' (which includes the bounds changes of a rotation) is changing.
+      // Marking a scaling transform as animating allows us to avoid resizing
+      // the texture, even if we have to repaint the contents of that texture.
+      if (layerActivity
+                  ->mRestyleCounts[LayerActivity::ACTIVITY_TRIGGERED_REPAINT] <
+              2 ||
+          (aPropertySet.Intersects(transformSet) &&
+           IsScaleSubjectToAnimation(aFrame))) {
+        return true;
+      }
+    }
+  }
+
+  if (nsLayoutUtils::HasEffectiveAnimation(aFrame, aPropertySet)) {
+    return true;
+  }
+
+  if (!aPropertySet.Intersects(transformSet) ||
+      !aFrame->Combines3DTransformWithAncestors()) {
+    return false;
+  }
+
+  // For preserve-3d, we check if there is any transform animation on its parent
+  // frames in the 3d rendering context. If there is one, this function will
+  // return true.
+  return IsStyleAnimated(aBuilder, aFrame->GetParent(), aPropertySet);
+}
+
+/* static */
+bool ActiveLayerTracker::IsScaleSubjectToAnimation(nsIFrame* aFrame) {
+  // Check whether JavaScript is animating this frame's scale.
+  LayerActivity* layerActivity = GetLayerActivity(aFrame);
+  if (layerActivity &&
+      layerActivity->mRestyleCounts[LayerActivity::ACTIVITY_SCALE] >= 2) {
+    return true;
+  }
+
+  return AnimationUtils::FrameHasAnimatedScale(aFrame);
+}
+
+/* static */
+void ActiveLayerTracker::Shutdown() { gLayerActivityTracker = nullptr; }
+
+}  // namespace mozilla