gecko-dev/gfx/layers/ScrollableLayerGuid.h

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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/. */
#ifndef GFX_SCROLLABLELAYERGUID_H
#define GFX_SCROLLABLELAYERGUID_H
#include <stdint.h> // for uint8_t, uint32_t, uint64_t
#include "mozilla/HashFunctions.h" // for HashGeneric
#include "mozilla/gfx/Logging.h" // for Log
#include "mozilla/layers/LayersTypes.h" // for LayersId
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;
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()
: mLayersId{0}
, mPresShellId(0)
, mScrollId(0)
{
}
ScrollableLayerGuid(LayersId aLayersId, uint32_t aPresShellId,
ViewID aScrollId)
: mLayersId(aLayersId)
, mPresShellId(aPresShellId)
, mScrollId(aScrollId)
{
}
ScrollableLayerGuid(const ScrollableLayerGuid& other)
: mLayersId(other.mLayersId)
, mPresShellId(other.mPresShellId)
, mScrollId(other.mScrollId)
{
}
~ScrollableLayerGuid()
{
}
bool operator==(const ScrollableLayerGuid& other) const
{
return mLayersId == other.mLayersId
&& mPresShellId == other.mPresShellId
&& mScrollId == other.mScrollId;
}
bool operator!=(const ScrollableLayerGuid& other) const
{
return !(*this == other);
}
bool operator<(const ScrollableLayerGuid& other) const
{
if (mLayersId < other.mLayersId) {
return true;
}
if (mLayersId == other.mLayersId) {
if (mPresShellId < other.mPresShellId) {
return true;
}
if (mPresShellId == other.mPresShellId) {
return mScrollId < other.mScrollId;
}
}
return false;
}
// 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
{
return HashGeneric(uint64_t(aGuid.mLayersId),
aGuid.mPresShellId,
aGuid.mScrollId);
}
};
struct HashIgnoringPresShellFn
{
std::size_t operator()(const ScrollableLayerGuid& aGuid) const
{
return HashGeneric(uint64_t(aGuid.mLayersId),
aGuid.mScrollId);
}
};
struct EqualIgnoringPresShellFn
{
bool operator()(const ScrollableLayerGuid& lhs, const ScrollableLayerGuid& rhs) const
{
return lhs.mLayersId == rhs.mLayersId
&& lhs.mScrollId == rhs.mScrollId;
}
};
};
template <int LogLevel>
gfx::Log<LogLevel>& operator<<(gfx::Log<LogLevel>& log, const ScrollableLayerGuid& aGuid) {
return log << '(' << uint64_t(aGuid.mLayersId) << ',' << aGuid.mPresShellId << ',' << aGuid.mScrollId << ')';
}
} // namespace layers
} // namespace mozilla
#endif /* GFX_SCROLLABLELAYERGUID_H */