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1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef CC_SCHEDULER_BEGIN_FRAME_TRACKER_H_ | |
6 #define CC_SCHEDULER_BEGIN_FRAME_TRACKER_H_ | |
7 | |
8 #include <set> | |
9 #include <string> | |
10 | |
11 #include "base/location.h" | |
12 #include "base/trace_event/trace_event.h" | |
13 #include "base/trace_event/trace_event_argument.h" | |
14 #include "cc/output/begin_frame_args.h" | |
15 | |
16 #define BEGINFRAMETRACKER_FROM_HERE FROM_HERE_WITH_EXPLICIT_FUNCTION("") | |
17 | |
18 namespace cc { | |
19 | |
20 // Microclass to trace and check properties for correct BeginFrameArgs (BFA) | |
21 // usage and provide a few helper methods. | |
22 // | |
23 // With DCHECKs enable, this class checks the following "invariants"; | |
24 // * BFA are monotonically increasing. | |
25 // * BFA is valid. | |
26 // * The BFA is only used inside a given period ( | |
brianderson
2015/05/01 02:05:21
Incomplete comment?
mithro-old
2015/05/01 03:27:56
Done.
| |
27 // * A new BFA isn't used before the last BFA is finished with. | |
28 // | |
29 // With the tracing category "cc.debug.scheduler.frames" enabled the tracker | |
30 // will output the following trace information; | |
31 // * Time period for which the BFA is in usage. | |
32 // * The flow of BFA as they are passed between tracking objects. | |
33 // | |
34 // TODO(mithro): Record stats about the BeginFrameArgs | |
35 class CC_EXPORT BeginFrameTracker { | |
36 public: | |
37 explicit BeginFrameTracker(const tracked_objects::Location& location); | |
38 ~BeginFrameTracker(); | |
39 | |
40 // The Start and Finish methods manage the period that a BFA should be | |
41 // accessed for. This allows tight control over the BFA and prevents | |
42 // accidental usage in the wrong period when code is split across multiple | |
43 // locations. | |
44 | |
45 // Start using a new BFA value and check invariant properties. | |
46 // **Must** only be called after finishing with any previous BFA. | |
47 void Start(BeginFrameArgs new_args); | |
48 // Finish using the current BFA. | |
49 // **Must** only be called while still using a BFA. | |
50 void Finish(); | |
51 | |
52 // The two accessors methods allow access to the BFA stored inside the | |
53 // tracker. They are mutually exclusive, at any time it is only valid to call | |
54 // one or the other. This makes sure you understand exactly which BFA you are | |
55 // intending to use and verifies that is the case. | |
56 | |
57 // Get the current BFA object. | |
58 // **Must** only be called between the start and finish methods calls. | |
59 const BeginFrameArgs& Current() const; | |
60 // Get the last used BFA. | |
61 // **Must** only be called when **not** between the start and finish method | |
62 // calls. | |
63 const BeginFrameArgs& Last() const; | |
64 | |
65 // Helper method to try and return a valid interval property. Defaults to | |
66 // BFA::DefaultInterval() is no other interval can be found. Can be called at | |
67 // any time. | |
68 base::TimeDelta Interval() const; | |
69 | |
70 void AsValueInto(base::TimeTicks now, | |
71 base::trace_event::TracedValue* dict) const; | |
72 | |
73 // The following methods violate principles of how BeginFrameArgs should be | |
74 // used. These methods should only be used when there is no other choice. | |
75 bool DangerousMethodHasStarted() const { | |
76 return !current_updated_at_.is_null(); | |
77 } | |
78 bool DangerousMethodHasFinished() const { return HasFinished(); } | |
79 const BeginFrameArgs& DangerousMethodCurrentOrLast() const; | |
80 | |
81 private: | |
82 // Return if currently not between the start/end period. This method should | |
83 // be used extremely sparingly and normal indicates incorrect management of | |
84 // the BFA object. Can be called at any time. | |
85 bool HasFinished() const { return !current_finished_at_.is_null(); } | |
86 | |
87 const tracked_objects::Location location_; | |
88 const std::string location_string_; | |
89 | |
90 base::TimeTicks current_updated_at_; | |
91 BeginFrameArgs current_args_; | |
92 base::TimeTicks current_finished_at_; | |
93 }; | |
94 | |
95 } // namespace cc | |
96 | |
97 #endif // CC_SCHEDULER_BEGIN_FRAME_TRACKER_H_ | |
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