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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
#ifndef GFX_WEBRENDERSCROLLDATAWRAPPER_H
#define GFX_WEBRENDERSCROLLDATAWRAPPER_H
#include "FrameMetrics.h"
#include "mozilla/layers/APZUpdater.h"
#include "mozilla/layers/CompositorBridgeParent.h"
#include "mozilla/layers/WebRenderBridgeParent.h"
#include "mozilla/layers/WebRenderScrollData.h"
namespace mozilla {
namespace layers {
/**
* A wrapper class around a target WebRenderLayerScrollData (henceforth,
* "layer") that allows user code to walk through the ScrollMetadata objects
* on the layer the same way it would walk through a layer tree.
* Consider the following layer tree:
*
* +---+
* | A |
* +---+
* / | \
* / | \
* / | \
* +---+ +-----+ +---+
* | B | | C | | D |
* +---+ +-----+ +---+
* | SMn |
* | . |
* | . |
* | . |
* | SM1 |
* | SM0 |
* +-----+
* / \
* / \
* +---+ +---+
* | E | | F |
* +---+ +---+
*
* In this layer tree, there are six layers with A being the root and B,D,E,F
* being leaf nodes. Layer C is in the middle and has n+1 ScrollMetadata,
* labelled SM0...SMn. SM0 is the ScrollMetadata you get by calling
* c->GetScrollMetadata(0) and SMn is the ScrollMetadata you can obtain by
* calling c->GetScrollMetadata(c->GetScrollMetadataCount() - 1). This layer
* tree is conceptually equivalent to this one below:
*
* +---+
* | A |
* +---+
* / | \
* / | \
* / | \
* +---+ +-----+ +---+
* | B | | Cn | | D |
* +---+ +-----+ +---+
* |
* .
* .
* .
* |
* +-----+
* | C1 |
* +-----+
* |
* +-----+
* | C0 |
* +-----+
* / \
* / \
* +---+ +---+
* | E | | F |
* +---+ +---+
*
* In this layer tree, the layer C has been expanded into a stack of layers
* C1...Cn, where C1 has ScrollMetadata SM1 and Cn has ScrollMetdata Fn.
*
* The WebRenderScrollDataWrapper class allows client code to treat the first
* layer tree as though it were the second. That is, instead of client code
* having to iterate through the ScrollMetadata objects directly, it can use a
* WebRenderScrollDataWrapper to encapsulate that aspect of the layer tree and
* just walk the tree as if it were a stack of layers.
*
* The functions on this class do different things depending on which
* simulated layer is being wrapped. For example, if the
* WebRenderScrollDataWrapper is pretending to be C0, the GetPrevSibling()
* function will return null even though the underlying layer C does actually
* have a prev sibling. The WebRenderScrollDataWrapper pretending to be Cn will
* return B as the prev sibling.
*
* Implementation notes:
*
* The AtTopLayer() and AtBottomLayer() functions in this class refer to
* Cn and C0 in the second layer tree above; that is, they are predicates
* to test if the wrapper is simulating the topmost or bottommost layer, as
* those can have special behaviour.
*
* It is possible to wrap a nullptr in a WebRenderScrollDataWrapper, in which
* case the IsValid() function will return false. This is required to allow
* WebRenderScrollDataWrapper to be a MOZ_STACK_CLASS (desirable because it is
* used in loops and recursion).
*
* This class purposely does not expose the wrapped layer directly to avoid
* user code from accidentally calling functions directly on it. Instead
* any necessary functions should be wrapped in this class. It does expose
* the wrapped layer as a void* for printf purposes.
*
* The implementation may look like it special-cases mIndex == 0 and/or
* GetScrollMetadataCount() == 0. This is an artifact of the fact that both
* mIndex and GetScrollMetadataCount() are uint32_t and GetScrollMetadataCount()
* can return 0 but mIndex cannot store -1. This seems better than the
* alternative of making mIndex a int32_t that can store -1, but then having
* to cast to uint32_t all over the place.
*
* Note that WebRenderLayerScrollData objects are owned by WebRenderScrollData,
* which stores them in a flattened representation. The field mData,
* mLayerIndex, and mContainingSubtreeIndex are used to move around the "layers"
* given the flattened representation. The mMetadataIndex is used to move around
* the ScrollMetadata within a single layer.
*
* One important note here is that this class holds a pointer to the "owning"
* WebRenderScrollData. The caller must ensure that this class does not outlive
* the owning WebRenderScrollData, or this may result in use-after-free errors.
* This class being declared a MOZ_STACK_CLASS should help with that.
*/
class MOZ_STACK_CLASS WebRenderScrollDataWrapper final {
public:
// Basic constructor for external callers. Starts the walker at the root of
// the tree.
explicit WebRenderScrollDataWrapper(
const APZUpdater& aUpdater, const WebRenderScrollData* aData = nullptr)
: mUpdater(&aUpdater),
mData(aData),
mLayerIndex(0),
mContainingSubtreeLastIndex(0),
mLayer(nullptr),
mMetadataIndex(0) {
if (!mData) {
return;
}
mLayer = mData->GetLayerData(mLayerIndex);
if (!mLayer) {
return;
}
// sanity check on the data
MOZ_ASSERT(mData->GetLayerCount() ==
(size_t)(1 + mLayer->GetDescendantCount()));
mContainingSubtreeLastIndex = mData->GetLayerCount();
// See documentation in LayerMetricsWrapper.h about this. mMetadataIndex
// in this class is equivalent to mIndex in that class.
mMetadataIndex = mLayer->GetScrollMetadataCount();
if (mMetadataIndex > 0) {
mMetadataIndex--;
}
}
private:
// Internal constructor for walking from one WebRenderLayerScrollData to
// another. In this case we need to recompute the mMetadataIndex to be the
// "topmost" scroll metadata on the new layer.
WebRenderScrollDataWrapper(const APZUpdater* aUpdater,
const WebRenderScrollData* aData,
size_t aLayerIndex,
size_t aContainingSubtreeLastIndex)
: mUpdater(aUpdater),
mData(aData),
mLayerIndex(aLayerIndex),
mContainingSubtreeLastIndex(aContainingSubtreeLastIndex),
mLayer(nullptr),
mMetadataIndex(0) {
MOZ_ASSERT(mData);
mLayer = mData->GetLayerData(mLayerIndex);
MOZ_ASSERT(mLayer);
// See documentation in LayerMetricsWrapper.h about this. mMetadataIndex
// in this class is equivalent to mIndex in that class.
mMetadataIndex = mLayer->GetScrollMetadataCount();
if (mMetadataIndex > 0) {
mMetadataIndex--;
}
}
// Internal constructor for walking from one metadata to another metadata on
// the same WebRenderLayerScrollData.
WebRenderScrollDataWrapper(const APZUpdater* aUpdater,
const WebRenderScrollData* aData,
size_t aLayerIndex,
size_t aContainingSubtreeLastIndex,
const WebRenderLayerScrollData* aLayer,
uint32_t aMetadataIndex)
: mUpdater(aUpdater),
mData(aData),
mLayerIndex(aLayerIndex),
mContainingSubtreeLastIndex(aContainingSubtreeLastIndex),
mLayer(aLayer),
mMetadataIndex(aMetadataIndex) {
MOZ_ASSERT(mData);
MOZ_ASSERT(mLayer);
MOZ_ASSERT(mLayer == mData->GetLayerData(mLayerIndex));
MOZ_ASSERT(mMetadataIndex == 0 ||
mMetadataIndex < mLayer->GetScrollMetadataCount());
}
public:
bool IsValid() const { return mLayer != nullptr; }
explicit operator bool() const { return IsValid(); }
WebRenderScrollDataWrapper GetLastChild() const {
MOZ_ASSERT(IsValid());
if (!AtBottomLayer()) {
// If we're still walking around in the virtual container layers created
// by the ScrollMetadata array, we just need to update the metadata index
// and that's it.
return WebRenderScrollDataWrapper(mUpdater, mData, mLayerIndex,
mContainingSubtreeLastIndex, mLayer,
mMetadataIndex - 1);
}
// Otherwise, we need to walk to a different WebRenderLayerScrollData in
// mData.
// Since mData contains the layer in depth-first, last-to-first order,
// the index after mLayerIndex must be mLayerIndex's last child, if it
// has any children (indicated by GetDescendantCount() > 0). Furthermore
// we compute the first index outside the subtree rooted at this node
// (in |subtreeLastIndex|) and pass that in to the child wrapper to use as
// its mContainingSubtreeLastIndex.
if (mLayer->GetDescendantCount() > 0) {
size_t prevSiblingIndex = mLayerIndex + 1 + mLayer->GetDescendantCount();
// TODO(botond): Replace the min() with just prevSiblingIndex (which
// should be <= mContainingSubtreeLastIndex).
MOZ_ASSERT(prevSiblingIndex <= mContainingSubtreeLastIndex);
size_t subtreeLastIndex =
std::min(mContainingSubtreeLastIndex, prevSiblingIndex);
return WebRenderScrollDataWrapper(mUpdater, mData, mLayerIndex + 1,
subtreeLastIndex);
}
// We've run out of descendants. But! If the original layer was a RefLayer,
// then it connects to another layer tree and we need to traverse that too.
// So return a WebRenderScrollDataWrapper for the root of the child layer
// tree.
if (mLayer->GetReferentId()) {
return WebRenderScrollDataWrapper(
*mUpdater, mUpdater->GetScrollData(*mLayer->GetReferentId()));
}
return WebRenderScrollDataWrapper(*mUpdater);
}
WebRenderScrollDataWrapper GetPrevSibling() const {
MOZ_ASSERT(IsValid());
if (!AtTopLayer()) {
// The virtual container layers don't have siblings
return WebRenderScrollDataWrapper(*mUpdater);
}
// Skip past the descendants to get to the previous sibling. However, we
// might be at the last sibling already.
size_t prevSiblingIndex = mLayerIndex + 1 + mLayer->GetDescendantCount();
if (prevSiblingIndex < mContainingSubtreeLastIndex) {
return WebRenderScrollDataWrapper(mUpdater, mData, prevSiblingIndex,
mContainingSubtreeLastIndex);
}
return WebRenderScrollDataWrapper(*mUpdater);
}
const ScrollMetadata& Metadata() const {
MOZ_ASSERT(IsValid());
if (mMetadataIndex >= mLayer->GetScrollMetadataCount()) {
return *ScrollMetadata::sNullMetadata;
}
return mLayer->GetScrollMetadata(*mData, mMetadataIndex);
}
const FrameMetrics& Metrics() const { return Metadata().GetMetrics(); }
AsyncPanZoomController* GetApzc() const { return nullptr; }
void SetApzc(AsyncPanZoomController* aApzc) const {}
const char* Name() const { return "WebRenderScrollDataWrapper"; }
gfx::Matrix4x4 GetTransform() const {
MOZ_ASSERT(IsValid());
// See WebRenderLayerScrollData::Initialize for more context.
// * The ancestor transform is associated with whichever layer has scroll
// id matching GetAncestorTransformId().
// * The transform is associated with the "bottommost" layer.
// Multiple transforms may apply to the same layer (e.g. if there is only
// one scrollmetadata on the layer, then it is both "topmost" and
// "bottommost"), so we may need to combine the transforms.
gfx::Matrix4x4 transform;
// The ancestor transform is usually emitted at the layer with the
// matching scroll id. However, sometimes the transform ends up on
// a node with no scroll metadata at all. In such cases we generate
// a single layer, and the ancestor transform needs to be on that layer,
// otherwise it will be lost.
bool emitAncestorTransform =
!Metrics().IsScrollable() ||
Metrics().GetScrollId() == mLayer->GetAncestorTransformId();
if (emitAncestorTransform) {
transform = mLayer->GetAncestorTransform();
}
if (AtBottomLayer()) {
transform = mLayer->GetTransform() * transform;
}
return transform;
}
CSSTransformMatrix GetTransformTyped() const {
return ViewAs<CSSTransformMatrix>(GetTransform());
}
bool TransformIsPerspective() const {
MOZ_ASSERT(IsValid());
// mLayer->GetTransformIsPerspective() tells us whether
// mLayer->GetTransform() is a perspective transform. Since
// mLayer->GetTransform() is only used at the bottom layer, we only
// need to check GetTransformIsPerspective() at the bottom layer too.
if (AtBottomLayer()) {
return mLayer->GetTransformIsPerspective();
}
return false;
}
LayerIntRect GetVisibleRect() const {
MOZ_ASSERT(IsValid());
if (AtBottomLayer()) {
return mLayer->GetVisibleRect();
}
return ViewAs<LayerPixel>(
TransformBy(mLayer->GetTransformTyped(), mLayer->GetVisibleRect()),
PixelCastJustification::MovingDownToChildren);
}
LayerIntSize GetRemoteDocumentSize() const {
MOZ_ASSERT(IsValid());
if (mLayer->GetReferentId().isNothing()) {
return LayerIntSize();
}
if (AtBottomLayer()) {
return mLayer->GetRemoteDocumentSize();
}
return ViewAs<LayerPixel>(mLayer->GetRemoteDocumentSize(),
PixelCastJustification::MovingDownToChildren);
}
Maybe<LayersId> GetReferentId() const {
MOZ_ASSERT(IsValid());
if (AtBottomLayer()) {
return mLayer->GetReferentId();
}
return Nothing();
}
EventRegionsOverride GetEventRegionsOverride() const {
MOZ_ASSERT(IsValid());
// Only ref layers can have an event regions override.
if (GetReferentId()) {
return mLayer->GetEventRegionsOverride();
}
return EventRegionsOverride::NoOverride;
}
const ScrollbarData& GetScrollbarData() const {
MOZ_ASSERT(IsValid());
return mLayer->GetScrollbarData();
}
Maybe<uint64_t> GetScrollbarAnimationId() const {
MOZ_ASSERT(IsValid());
return mLayer->GetScrollbarAnimationId();
}
Maybe<uint64_t> GetFixedPositionAnimationId() const {
MOZ_ASSERT(IsValid());
if (AtBottomLayer()) {
return mLayer->GetFixedPositionAnimationId();
}
return Nothing();
}
ScrollableLayerGuid::ViewID GetFixedPositionScrollContainerId() const {
MOZ_ASSERT(IsValid());
if (AtBottomLayer()) {
return mLayer->GetFixedPositionScrollContainerId();
}
return ScrollableLayerGuid::NULL_SCROLL_ID;
}
SideBits GetFixedPositionSides() const {
MOZ_ASSERT(IsValid());
if (AtBottomLayer()) {
return mLayer->GetFixedPositionSides();
}
return SideBits::eNone;
}
ScrollableLayerGuid::ViewID GetStickyScrollContainerId() const {
MOZ_ASSERT(IsValid());
if (AtBottomLayer()) {
return mLayer->GetStickyPositionScrollContainerId();
}
return ScrollableLayerGuid::NULL_SCROLL_ID;
}
const LayerRectAbsolute& GetStickyScrollRangeOuter() const {
MOZ_ASSERT(IsValid());
if (AtBottomLayer()) {
return mLayer->GetStickyScrollRangeOuter();
}
static const LayerRectAbsolute empty;
return empty;
}
const LayerRectAbsolute& GetStickyScrollRangeInner() const {
MOZ_ASSERT(IsValid());
if (AtBottomLayer()) {
return mLayer->GetStickyScrollRangeInner();
}
static const LayerRectAbsolute empty;
return empty;
}
Maybe<uint64_t> GetStickyPositionAnimationId() const {
MOZ_ASSERT(IsValid());
if (AtBottomLayer()) {
return mLayer->GetStickyPositionAnimationId();
}
return Nothing();
}
Maybe<uint64_t> GetZoomAnimationId() const {
MOZ_ASSERT(IsValid());
return mLayer->GetZoomAnimationId();
}
Maybe<ScrollableLayerGuid::ViewID> GetAsyncZoomContainerId() const {
MOZ_ASSERT(IsValid());
return mLayer->GetAsyncZoomContainerId();
}
// Expose an opaque pointer to the layer. Mostly used for printf
// purposes. This is not intended to be a general-purpose accessor
// for the underlying layer.
const void* GetLayer() const {
MOZ_ASSERT(IsValid());
return mLayer;
}
template <int Level>
size_t Dump(gfx::TreeLog<Level>& aOut) const {
std::string result = "(invalid)";
if (!IsValid()) {
aOut << result;
return result.length();
}
if (AtBottomLayer()) {
if (mData != nullptr) {
const WebRenderLayerScrollData* layerData =
mData->GetLayerData(mLayerIndex);
if (layerData != nullptr) {
std::stringstream ss;
layerData->Dump(ss, *mData);
result = ss.str();
aOut << result;
return result.length();
}
}
}
return 0;
}
private:
bool AtBottomLayer() const { return mMetadataIndex == 0; }
bool AtTopLayer() const {
return mLayer->GetScrollMetadataCount() == 0 ||
mMetadataIndex == mLayer->GetScrollMetadataCount() - 1;
}
private:
const APZUpdater* mUpdater;
const WebRenderScrollData* mData;
// The index (in mData->mLayerScrollData) of the WebRenderLayerScrollData this
// wrapper is pointing to.
size_t mLayerIndex;
// The upper bound on the set of valid indices inside the subtree rooted at
// the parent of this "layer". That is, any layer index |i| in the range
// mLayerIndex <= i < mContainingSubtreeLastIndex is guaranteed to point to
// a layer that is a descendant of "parent", where "parent" is the parent
// layer of the layer at mLayerIndex. This is needed in order to implement
// GetPrevSibling() correctly.
size_t mContainingSubtreeLastIndex;
// The WebRenderLayerScrollData this wrapper is pointing to.
const WebRenderLayerScrollData* mLayer;
// The index of the scroll metadata within mLayer that this wrapper is
// pointing to.
uint32_t mMetadataIndex;
};
} // namespace layers
} // namespace mozilla
#endif /* GFX_WEBRENDERSCROLLDATAWRAPPER_H */