1// Copyright 2013 The Flutter 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#include "flutter/shell/common/vsync_waiter.h"
6
7#include "flutter/fml/task_runner.h"
8#include "flutter/fml/trace_event.h"
9
10namespace flutter {
11
12static constexpr const char* kVsyncFlowName = "VsyncFlow";
13
14#if defined(OS_FUCHSIA)
15// ________ _________ ________ ________
16// |\ ____\|\___ ___\\ __ \|\ __ \
17// \ \ \___|\|___ \ \_\ \ \|\ \ \ \|\ \
18// \ \_____ \ \ \ \ \ \ \\\ \ \ ____\
19// \|____|\ \ \ \ \ \ \ \\\ \ \ \___|
20// ____\_\ \ \ \__\ \ \_______\ \__\
21// |\_________\ \|__| \|_______|\|__|
22// \|_________|
23//
24// Fuchsia benchmarks depend on this trace event's name. Please do not change
25// it without checking that the changes are compatible with Fuchsia benchmarks
26// first!
27static constexpr const char* kVsyncTraceName = "vsync callback";
28#else
29static constexpr const char* kVsyncTraceName = "VsyncProcessCallback";
30#endif
31
32VsyncWaiter::VsyncWaiter(TaskRunners task_runners)
33 : task_runners_(std::move(task_runners)) {}
34
35VsyncWaiter::~VsyncWaiter() = default;
36
37// Public method invoked by the animator.
38void VsyncWaiter::AsyncWaitForVsync(const Callback& callback) {
39 if (!callback) {
40 return;
41 }
42
43 TRACE_EVENT0("flutter", "AsyncWaitForVsync");
44
45 {
46 std::scoped_lock lock(callback_mutex_);
47 if (callback_) {
48 // The animator may request a frame more than once within a frame
49 // interval. Multiple calls to request frame must result in a single
50 // callback per frame interval.
51 TRACE_EVENT_INSTANT0("flutter", "MultipleCallsToVsyncInFrameInterval");
52 return;
53 }
54 callback_ = std::move(callback);
55 if (secondary_callback_) {
56 // Return directly as `AwaitVSync` is already called by
57 // `ScheduleSecondaryCallback`.
58 return;
59 }
60 }
61 AwaitVSync();
62}
63
64void VsyncWaiter::ScheduleSecondaryCallback(const fml::closure& callback) {
65 FML_DCHECK(task_runners_.GetUITaskRunner()->RunsTasksOnCurrentThread());
66
67 if (!callback) {
68 return;
69 }
70
71 TRACE_EVENT0("flutter", "ScheduleSecondaryCallback");
72
73 {
74 std::scoped_lock lock(callback_mutex_);
75 if (secondary_callback_) {
76 // Multiple schedules must result in a single callback per frame interval.
77 TRACE_EVENT_INSTANT0("flutter",
78 "MultipleCallsToSecondaryVsyncInFrameInterval");
79 return;
80 }
81 secondary_callback_ = std::move(callback);
82 if (callback_) {
83 // Return directly as `AwaitVSync` is already called by
84 // `AsyncWaitForVsync`.
85 return;
86 }
87 }
88 AwaitVSync();
89}
90
91void VsyncWaiter::FireCallback(fml::TimePoint frame_start_time,
92 fml::TimePoint frame_target_time) {
93 Callback callback;
94 fml::closure secondary_callback;
95
96 {
97 std::scoped_lock lock(callback_mutex_);
98 callback = std::move(callback_);
99 secondary_callback = std::move(secondary_callback_);
100 }
101
102 if (!callback && !secondary_callback) {
103 // This means that the vsync waiter implementation fired a callback for a
104 // request we did not make. This is a paranoid check but we still want to
105 // make sure we catch misbehaving vsync implementations.
106 TRACE_EVENT_INSTANT0("flutter", "MismatchedFrameCallback");
107 return;
108 }
109
110 if (callback) {
111 auto flow_identifier = fml::tracing::TraceNonce();
112
113 // The base trace ensures that flows have a root to begin from if one does
114 // not exist. The trace viewer will ignore traces that have no base event
115 // trace. While all our message loops insert a base trace trace
116 // (MessageLoop::RunExpiredTasks), embedders may not.
117 TRACE_EVENT0("flutter", "VsyncFireCallback");
118
119 TRACE_FLOW_BEGIN("flutter", kVsyncFlowName, flow_identifier);
120
121 task_runners_.GetUITaskRunner()->PostTaskForTime(
122 [callback, flow_identifier, frame_start_time, frame_target_time]() {
123 FML_TRACE_EVENT("flutter", kVsyncTraceName, "StartTime",
124 frame_start_time, "TargetTime", frame_target_time);
125 callback(frame_start_time, frame_target_time);
126 TRACE_FLOW_END("flutter", kVsyncFlowName, flow_identifier);
127 },
128 frame_start_time);
129 }
130
131 if (secondary_callback) {
132 task_runners_.GetUITaskRunner()->PostTaskForTime(
133 std::move(secondary_callback), frame_start_time);
134 }
135}
136
137float VsyncWaiter::GetDisplayRefreshRate() const {
138 return kUnknownRefreshRateFPS;
139}
140
141} // namespace flutter
142