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1 // Copyright 2016 The Chromium Authors. All rights reserved. | 1 // Copyright 2016 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #ifndef CC_TREES_ELEMENT_ID_H_ | 5 #ifndef CC_TREES_ELEMENT_ID_H_ |
6 #define CC_TREES_ELEMENT_ID_H_ | 6 #define CC_TREES_ELEMENT_ID_H_ |
7 | 7 |
8 #include <stddef.h> | 8 #include <stdint.h> |
9 | |
10 #include <cstdint> | |
11 #include <functional> | |
12 #include <iosfwd> | |
13 #include <memory> | |
14 | |
15 #include "base/hash.h" | |
16 #include "cc/cc_export.h" | |
17 | |
18 namespace base { | |
19 class Value; | |
20 namespace trace_event { | |
21 class TracedValue; | |
22 } // namespace trace_event | |
23 } // namespace base | |
24 | 9 |
25 namespace cc { | 10 namespace cc { |
26 | 11 |
27 // Element ids are chosen by cc's clients and can be used as a stable identifier | 12 using ElementId = uint64_t; |
wkorman
2017/05/05 20:06:10
Shouldn't we keep some of this documentation? Or,
chrishtr
2017/05/05 20:46:09
Oh right. Re-added.
| |
28 // across updates. | |
29 // | |
30 // Historically, the layer tree stored all compositing data but this has been | |
31 // refactored over time into auxilliary structures such as property trees. | |
32 // | |
33 // In composited scrolling, Layers directly reference scroll tree nodes | |
34 // (Layer::scroll_tree_index) but scroll tree nodes are being refactored to | |
35 // reference stable element ids instead of layers. Scroll property nodes have | |
36 // unique element ids that blink creates from scrollable areas (though this is | |
37 // opaque to the compositor). This refactoring of scroll nodes keeping a | |
38 // scrolling element id instead of a scrolling layer id allows for more general | |
39 // compositing where, for example, multiple layers scroll with one scroll node. | |
40 // | |
41 // The animation system (see: ElementAnimations and blink::ElementAnimations) is | |
42 // another auxilliary structure to the layer tree and uses element ids as a | |
43 // stable identifier for animation targets. A Layer's element id can change over | |
44 // the Layer's lifetime because non-default ElementIds are only set during an | |
45 // animation's lifetime. | |
46 struct CC_EXPORT ElementId { | |
47 ElementId(int primaryId, int secondaryId) | |
48 : primaryId(primaryId), secondaryId(secondaryId) {} | |
49 ElementId() : ElementId(0, 0) {} | |
50 | 13 |
51 bool operator==(const ElementId& o) const; | 14 static const ElementId kInvalidElementId = 0; |
52 bool operator!=(const ElementId& o) const; | |
53 bool operator<(const ElementId& o) const; | |
54 | |
55 // An ElementId's conversion to a boolean value depends only on its primaryId. | |
56 explicit operator bool() const; | |
57 | |
58 void AddToTracedValue(base::trace_event::TracedValue* res) const; | |
59 std::unique_ptr<base::Value> AsValue() const; | |
60 | |
61 // The compositor treats this as an opaque handle and should not know how to | |
62 // interpret these bits. Non-blink cc clients typically operate in terms of | |
63 // layers and may set this value to match the client's layer id. | |
64 int primaryId; | |
65 int secondaryId; | |
66 }; | |
67 | |
68 CC_EXPORT ElementId LayerIdToElementIdForTesting(int layer_id); | |
69 | |
70 struct CC_EXPORT ElementIdHash { | |
71 size_t operator()(ElementId key) const; | |
72 }; | |
73 | |
74 // Stream operator so ElementId can be used in assertion statements. | |
75 CC_EXPORT std::ostream& operator<<(std::ostream& out, const ElementId& id); | |
wkorman
2017/05/05 20:06:10
It occurs to me, just to mention another non obvio
| |
76 | 15 |
77 } // namespace cc | 16 } // namespace cc |
78 | 17 |
79 #endif // CC_TREES_ELEMENT_ID_H_ | 18 #endif // CC_TREES_ELEMENT_ID_H_ |
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