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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 */
#include <iosfwd> // for ostream
#include <stdint.h> // for uint8_t, uint32_t, uint64_t
#include "mozilla/layers/LayersTypes.h" // for LayersId
#include "nsHashKeys.h" // for nsUint64HashKey
namespace mozilla {
namespace layers {
* This class allows us to uniquely identify a scrollable layer. The
* mLayersId identifies the layer tree (corresponding to a child process
* and/or tab) that the scrollable layer belongs to. The mPresShellId
* is a temporal identifier (corresponding to the document loaded that
* contains the scrollable layer, which may change over time). The
* mScrollId corresponds to the actual frame that is scrollable.
struct ScrollableLayerGuid {
// We use IDs to identify frames across processes.
typedef uint64_t ViewID;
typedef nsUint64HashKey ViewIDHashKey;
static const ViewID NULL_SCROLL_ID; // This container layer does not scroll.
static const ViewID START_SCROLL_ID = 2; // This is the ID that scrolling
// subframes will begin at.
LayersId mLayersId;
uint32_t mPresShellId;
ViewID mScrollId;
ScrollableLayerGuid(LayersId aLayersId, uint32_t aPresShellId,
ViewID aScrollId);
ScrollableLayerGuid(const ScrollableLayerGuid& other) = default;
~ScrollableLayerGuid() = default;
bool operator==(const ScrollableLayerGuid& other) const;
bool operator!=(const ScrollableLayerGuid& other) const;
bool operator<(const ScrollableLayerGuid& other) const;
friend std::ostream& operator<<(std::ostream& aOut,
const ScrollableLayerGuid& aGuid);
using Comparator = bool (*)(const ScrollableLayerGuid&,
const ScrollableLayerGuid&);
static bool EqualsIgnoringPresShell(const ScrollableLayerGuid& aA,
const ScrollableLayerGuid& aB);
// Helper structs to use as hash/equality functions in std::unordered_map.
// e.g. std::unordered_map<ScrollableLayerGuid,
// ValueType,
// ScrollableLayerGuid::HashFn> myMap;
// std::unordered_map<ScrollableLayerGuid,
// ValueType,
// ScrollableLayerGuid::HashIgnoringPresShellFn,
// ScrollableLayerGuid::EqualIgnoringPresShellFn> myMap;
struct HashFn {
std::size_t operator()(const ScrollableLayerGuid& aGuid) const;
struct HashIgnoringPresShellFn {
std::size_t operator()(const ScrollableLayerGuid& aGuid) const;
struct EqualIgnoringPresShellFn {
bool operator()(const ScrollableLayerGuid& lhs,
const ScrollableLayerGuid& rhs) const;
} // namespace layers
} // namespace mozilla