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/* 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 */
#ifndef mozilla_ScrollGeneration_h_
#define mozilla_ScrollGeneration_h_
#include <cstdint>
#include <iosfwd>
namespace mozilla {
struct ScrollGenerationCounter;
class APZTag {};
class MainThreadTag {};
template <typename Tag>
struct ScrollGeneration;
template <typename Tag>
std::ostream& operator<<(std::ostream& aStream,
const ScrollGeneration<Tag>& aGen);
template <typename Tag>
struct ScrollGeneration {
friend struct ScrollGenerationCounter;
// Private constructor; use ScrollGenerationCounter to get a new instance.
explicit ScrollGeneration(uint64_t aValue);
// Dummy constructor, needed for IPDL purposes. Not intended for manual use.
uint64_t Raw() const { return mValue; }
bool operator<(const ScrollGeneration<Tag>& aOther) const;
bool operator==(const ScrollGeneration<Tag>& aOther) const;
bool operator!=(const ScrollGeneration<Tag>& aOther) const;
friend std::ostream& operator<< <>(std::ostream& aStream,
const ScrollGeneration<Tag>& aGen);
uint64_t mValue;
using APZScrollGeneration = ScrollGeneration<APZTag>;
using MainThreadScrollGeneration = ScrollGeneration<MainThreadTag>;
struct ScrollGenerationCounter {
MainThreadScrollGeneration NewMainThreadGeneration() {
uint64_t value = ++mCounter;
return MainThreadScrollGeneration(value);
APZScrollGeneration NewAPZGeneration() {
uint64_t value = ++mCounter;
return APZScrollGeneration(value);
uint64_t mCounter = 0;
} // namespace mozilla
#endif // mozilla_ScrollGeneration_h_