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-rw-r--r--gfx/layers/ScrollableLayerGuid.h86
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diff --git a/gfx/layers/ScrollableLayerGuid.h b/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 <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();
+
+ 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
+
+#endif /* GFX_SCROLLABLELAYERGUID_H */