1 files changed, 342 insertions, 0 deletions
diff --git a/gfx/layers/FrameMetrics.cpp b/gfx/layers/FrameMetrics.cpp
new file mode 100644
index 0000000000..eb84d22db6
--- /dev/null
+++ b/gfx/layers/FrameMetrics.cpp
@@ -0,0 +1,342 @@
+/* -*- 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 "FrameMetrics.h"
+
+#include <ostream>
+
+#include "gfxUtils.h"
+#include "nsStyleConsts.h"
+#include "nsStyleStruct.h"
+#include "mozilla/WritingModes.h"
+#include "mozilla/gfx/Types.h"
+
+namespace mozilla {
+namespace layers {
+
+const ScrollableLayerGuid::ViewID ScrollableLayerGuid::NULL_SCROLL_ID = 0;
+
+std::ostream& operator<<(std::ostream& aStream, const FrameMetrics& aMetrics) {
+  aStream << "{ [cb=" << aMetrics.GetCompositionBounds()
+          << "] [sr=" << aMetrics.GetScrollableRect()
+          << "] [s=" << aMetrics.GetVisualScrollOffset();
+  if (aMetrics.GetVisualScrollUpdateType() != FrameMetrics::eNone) {
+    aStream << "] [vd=" << aMetrics.GetVisualDestination();
+  }
+  if (aMetrics.IsScrollInfoLayer()) {
+    aStream << "] [scrollinfo";
+  }
+  aStream << "] [dp=" << aMetrics.GetDisplayPort()
+          << "] [rcs=" << aMetrics.GetBoundingCompositionSize()
+          << "] [v=" << aMetrics.GetLayoutViewport()
+          << nsPrintfCString("] [z=(ld=%.3f r=%.3f",
+                             aMetrics.GetDevPixelsPerCSSPixel().scale,
+                             aMetrics.GetPresShellResolution())
+                 .get()
+          << " cr=" << aMetrics.GetCumulativeResolution()
+          << " z=" << aMetrics.GetZoom()
+          << " t=" << aMetrics.GetTransformToAncestorScale() << " )] [u=("
+          << (int)aMetrics.GetVisualScrollUpdateType() << " "
+          << aMetrics.GetScrollGeneration()
+          << ")] scrollId=" << aMetrics.GetScrollId();
+  if (aMetrics.IsRootContent()) {
+    aStream << " [rcd]";
+  }
+  aStream << " }";
+  return aStream;
+}
+
+void FrameMetrics::RecalculateLayoutViewportOffset() {
+  // For subframes, the visual and layout viewports coincide, so just
+  // keep the layout viewport offset in sync with the visual one.
+  if (!mIsRootContent) {
+    mLayoutViewport.MoveTo(GetVisualScrollOffset());
+    return;
+  }
+  // For the root, the two viewports can diverge, but the layout
+  // viewport needs to keep enclosing the visual viewport.
+  KeepLayoutViewportEnclosingVisualViewport(GetVisualViewport(),
+                                            mScrollableRect, mLayoutViewport);
+}
+
+/* static */
+void FrameMetrics::KeepLayoutViewportEnclosingVisualViewport(
+    const CSSRect& aVisualViewport, const CSSRect& aScrollableRect,
+    CSSRect& aLayoutViewport) {
+  // If the visual viewport is contained within the layout viewport, we don't
+  // need to make any adjustments, so we can exit early.
+  //
+  // Additionally, if the composition bounds changes (due to an orientation
+  // change, window resize, etc.), it may take a few frames for aLayoutViewport
+  // to update and during that time, the visual viewport may be larger than the
+  // layout viewport. In such situations, we take an early exit if the visual
+  // viewport contains the layout viewport.
+  if (aLayoutViewport.Contains(aVisualViewport) ||
+      aVisualViewport.Contains(aLayoutViewport)) {
+    return;
+  }
+
+  // If visual viewport size is greater than the layout viewport, move the
+  // layout viewport such that it remains inside the visual viewport. Otherwise,
+  // move the layout viewport such that the visual viewport is contained
+  // inside the layout viewport.
+  if ((aLayoutViewport.Width() < aVisualViewport.Width() &&
+       !FuzzyEqualsMultiplicative(aLayoutViewport.Width(),
+                                  aVisualViewport.Width())) ||
+      (aLayoutViewport.Height() < aVisualViewport.Height() &&
+       !FuzzyEqualsMultiplicative(aLayoutViewport.Height(),
+                                  aVisualViewport.Height()))) {
+    if (aLayoutViewport.X() < aVisualViewport.X()) {
+      // layout viewport moves right
+      aLayoutViewport.MoveToX(aVisualViewport.X());
+    } else if (aVisualViewport.XMost() < aLayoutViewport.XMost()) {
+      // layout viewport moves left
+      aLayoutViewport.MoveByX(aVisualViewport.XMost() -
+                              aLayoutViewport.XMost());
+    }
+    if (aLayoutViewport.Y() < aVisualViewport.Y()) {
+      // layout viewport moves down
+      aLayoutViewport.MoveToY(aVisualViewport.Y());
+    } else if (aVisualViewport.YMost() < aLayoutViewport.YMost()) {
+      // layout viewport moves up
+      aLayoutViewport.MoveByY(aVisualViewport.YMost() -
+                              aLayoutViewport.YMost());
+    }
+  } else {
+    if (aVisualViewport.X() < aLayoutViewport.X()) {
+      aLayoutViewport.MoveToX(aVisualViewport.X());
+    } else if (aLayoutViewport.XMost() < aVisualViewport.XMost()) {
+      aLayoutViewport.MoveByX(aVisualViewport.XMost() -
+                              aLayoutViewport.XMost());
+    }
+    if (aVisualViewport.Y() < aLayoutViewport.Y()) {
+      aLayoutViewport.MoveToY(aVisualViewport.Y());
+    } else if (aLayoutViewport.YMost() < aVisualViewport.YMost()) {
+      aLayoutViewport.MoveByY(aVisualViewport.YMost() -
+                              aLayoutViewport.YMost());
+    }
+  }
+
+  // Regardless of any adjustment above, the layout viewport is not allowed
+  // to go outside the scrollable rect.
+  aLayoutViewport = aLayoutViewport.MoveInsideAndClamp(aScrollableRect);
+}
+
+/* static */
+CSSRect FrameMetrics::CalculateScrollRange(
+    const CSSRect& aScrollableRect, const ParentLayerRect& aCompositionBounds,
+    const CSSToParentLayerScale& aZoom) {
+  CSSSize scrollPortSize =
+      CalculateCompositedSizeInCssPixels(aCompositionBounds, aZoom);
+  CSSRect scrollRange = aScrollableRect;
+  scrollRange.SetWidth(
+      std::max(scrollRange.Width() - scrollPortSize.width, 0.0f));
+  scrollRange.SetHeight(
+      std::max(scrollRange.Height() - scrollPortSize.height, 0.0f));
+  return scrollRange;
+}
+
+/* static */
+CSSSize FrameMetrics::CalculateCompositedSizeInCssPixels(
+    const ParentLayerRect& aCompositionBounds,
+    const CSSToParentLayerScale& aZoom) {
+  if (aZoom == CSSToParentLayerScale(0)) {
+    return CSSSize();  // avoid division by zero
+  }
+  return aCompositionBounds.Size() / aZoom;
+}
+
+bool FrameMetrics::ApplyScrollUpdateFrom(const ScrollPositionUpdate& aUpdate) {
+  // In applying a main-thread scroll update, try to preserve the relative
+  // offset between the visual and layout viewports.
+  CSSPoint relativeOffset = GetVisualScrollOffset() - GetLayoutScrollOffset();
+  MOZ_ASSERT(IsRootContent() || relativeOffset == CSSPoint());
+  // We need to set the two offsets together, otherwise a subsequent
+  // RecalculateLayoutViewportOffset() could see divergent layout and
+  // visual offsets.
+  bool offsetChanged = SetLayoutScrollOffset(aUpdate.GetDestination());
+  offsetChanged |=
+      ClampAndSetVisualScrollOffset(aUpdate.GetDestination() + relativeOffset);
+  return offsetChanged;
+}
+
+CSSPoint FrameMetrics::ApplyRelativeScrollUpdateFrom(
+    const ScrollPositionUpdate& aUpdate) {
+  MOZ_ASSERT(aUpdate.GetType() == ScrollUpdateType::Relative);
+  CSSPoint origin = GetVisualScrollOffset();
+  CSSPoint delta = (aUpdate.GetDestination() - aUpdate.GetSource());
+  ClampAndSetVisualScrollOffset(origin + delta);
+  return GetVisualScrollOffset() - origin;
+}
+
+CSSPoint FrameMetrics::ApplyPureRelativeScrollUpdateFrom(
+    const ScrollPositionUpdate& aUpdate) {
+  MOZ_ASSERT(aUpdate.GetType() == ScrollUpdateType::PureRelative);
+  CSSPoint origin = GetVisualScrollOffset();
+  ClampAndSetVisualScrollOffset(origin + aUpdate.GetDelta());
+  return GetVisualScrollOffset() - origin;
+}
+
+void FrameMetrics::UpdatePendingScrollInfo(const ScrollPositionUpdate& aInfo) {
+  // We only get this "pending scroll info" for paint-skip transactions,
+  // but PureRelative position updates always trigger a full paint, so
+  // we should never enter this code with a PureRelative update type. For
+  // the other types, the destination field on the ScrollPositionUpdate will
+  // tell us the final layout scroll position on the main thread.
+  MOZ_ASSERT(aInfo.GetType() != ScrollUpdateType::PureRelative);
+
+  // In applying a main-thread scroll update, try to preserve the relative
+  // offset between the visual and layout viewports.
+  CSSPoint relativeOffset = GetVisualScrollOffset() - GetLayoutScrollOffset();
+  MOZ_ASSERT(IsRootContent() || relativeOffset == CSSPoint());
+
+  SetLayoutScrollOffset(aInfo.GetDestination());
+  ClampAndSetVisualScrollOffset(aInfo.GetDestination() + relativeOffset);
+  mScrollGeneration = aInfo.GetGeneration();
+}
+
+ScrollSnapInfo::ScrollSnapInfo()
+    : mScrollSnapStrictnessX(StyleScrollSnapStrictness::None),
+      mScrollSnapStrictnessY(StyleScrollSnapStrictness::None) {}
+
+bool ScrollSnapInfo::HasScrollSnapping() const {
+  return mScrollSnapStrictnessY != StyleScrollSnapStrictness::None ||
+         mScrollSnapStrictnessX != StyleScrollSnapStrictness::None;
+}
+
+bool ScrollSnapInfo::HasSnapPositions() const {
+  if (!HasScrollSnapping()) {
+    return false;
+  }
+
+  for (const auto& target : mSnapTargets) {
+    if ((target.mSnapPositionX &&
+         mScrollSnapStrictnessX != StyleScrollSnapStrictness::None) ||
+        (target.mSnapPositionY &&
+         mScrollSnapStrictnessY != StyleScrollSnapStrictness::None)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void ScrollSnapInfo::InitializeScrollSnapStrictness(
+    WritingMode aWritingMode, const nsStyleDisplay* aDisplay) {
+  if (aDisplay->mScrollSnapType.strictness == StyleScrollSnapStrictness::None) {
+    return;
+  }
+
+  mScrollSnapStrictnessX = StyleScrollSnapStrictness::None;
+  mScrollSnapStrictnessY = StyleScrollSnapStrictness::None;
+
+  switch (aDisplay->mScrollSnapType.axis) {
+    case StyleScrollSnapAxis::X:
+      mScrollSnapStrictnessX = aDisplay->mScrollSnapType.strictness;
+      break;
+    case StyleScrollSnapAxis::Y:
+      mScrollSnapStrictnessY = aDisplay->mScrollSnapType.strictness;
+      break;
+    case StyleScrollSnapAxis::Block:
+      if (aWritingMode.IsVertical()) {
+        mScrollSnapStrictnessX = aDisplay->mScrollSnapType.strictness;
+      } else {
+        mScrollSnapStrictnessY = aDisplay->mScrollSnapType.strictness;
+      }
+      break;
+    case StyleScrollSnapAxis::Inline:
+      if (aWritingMode.IsVertical()) {
+        mScrollSnapStrictnessY = aDisplay->mScrollSnapType.strictness;
+      } else {
+        mScrollSnapStrictnessX = aDisplay->mScrollSnapType.strictness;
+      }
+      break;
+    case StyleScrollSnapAxis::Both:
+      mScrollSnapStrictnessX = aDisplay->mScrollSnapType.strictness;
+      mScrollSnapStrictnessY = aDisplay->mScrollSnapType.strictness;
+      break;
+  }
+}
+
+std::ostream& operator<<(std::ostream& aStream,
+                         const OverscrollBehavior& aBehavior) {
+  switch (aBehavior) {
+    case OverscrollBehavior::Auto: {
+      aStream << "auto";
+      break;
+    }
+    case OverscrollBehavior::Contain: {
+      aStream << "contain";
+      break;
+    }
+    case OverscrollBehavior::None: {
+      aStream << "none";
+      break;
+    }
+  }
+  return aStream;
+}
+
+OverscrollBehaviorInfo::OverscrollBehaviorInfo()
+    : mBehaviorX(OverscrollBehavior::Auto),
+      mBehaviorY(OverscrollBehavior::Auto) {}
+
+static OverscrollBehavior ToOverscrollBehavior(
+    StyleOverscrollBehavior aBehavior) {
+  switch (aBehavior) {
+    case StyleOverscrollBehavior::Auto:
+      return OverscrollBehavior::Auto;
+    case StyleOverscrollBehavior::Contain:
+      return OverscrollBehavior::Contain;
+    case StyleOverscrollBehavior::None:
+      return OverscrollBehavior::None;
+  }
+  MOZ_ASSERT_UNREACHABLE("Invalid overscroll behavior");
+  return OverscrollBehavior::Auto;
+}
+
+OverscrollBehaviorInfo OverscrollBehaviorInfo::FromStyleConstants(
+    StyleOverscrollBehavior aBehaviorX, StyleOverscrollBehavior aBehaviorY) {
+  OverscrollBehaviorInfo result;
+  result.mBehaviorX = ToOverscrollBehavior(aBehaviorX);
+  result.mBehaviorY = ToOverscrollBehavior(aBehaviorY);
+  return result;
+}
+
+bool OverscrollBehaviorInfo::operator==(
+    const OverscrollBehaviorInfo& aOther) const {
+  return mBehaviorX == aOther.mBehaviorX && mBehaviorY == aOther.mBehaviorY;
+}
+
+std::ostream& operator<<(std::ostream& aStream,
+                         const OverscrollBehaviorInfo& aInfo) {
+  if (aInfo.mBehaviorX == aInfo.mBehaviorY) {
+    aStream << aInfo.mBehaviorX;
+  } else {
+    aStream << "{ x=" << aInfo.mBehaviorX << ", y=" << aInfo.mBehaviorY << " }";
+  }
+  return aStream;
+}
+
+std::ostream& operator<<(std::ostream& aStream,
+                         const ScrollMetadata& aMetadata) {
+  aStream << "{ [description=" << aMetadata.GetContentDescription()
+          << "] [metrics=" << aMetadata.GetMetrics();
+  if (aMetadata.GetScrollParentId() != ScrollableLayerGuid::NULL_SCROLL_ID) {
+    aStream << "] [scrollParent=" << aMetadata.GetScrollParentId();
+  }
+  if (aMetadata.GetHasScrollgrab()) {
+    aStream << "] [scrollgrab";
+  }
+  aStream << "] [overscroll=" << aMetadata.GetOverscrollBehavior() << "] ["
+          << aMetadata.GetScrollUpdates().Length() << " scrollupdates"
+          << "] }";
+  return aStream;
+}
+
+StaticAutoPtr<const ScrollMetadata> ScrollMetadata::sNullMetadata;
+
+}  // namespace layers
+}  // namespace mozilla