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Smooth out iOS irregular input events delivery #11817
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| // Copyright 2013 The Flutter Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license that can be | ||
| // found in the LICENSE file. | ||
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| #include "flutter/shell/common/shell_test.h" | ||
|
Contributor
There was a problem hiding this comment. Good call on putting these in their own TU. Makes things a lot clearer. |
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| #include "flutter/testing/testing.h" | ||
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| namespace flutter { | ||
| namespace testing { | ||
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| // Throughout these tests, the choice of time unit is irrelevant as long as all | ||
| // times have the same units. | ||
| using UnitlessTime = int; | ||
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| // Signature of a generator function that takes the frame index as input and | ||
| // returns the time of that frame. | ||
| using Generator = std::function<UnitlessTime(int)>; | ||
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| //---------------------------------------------------------------------------- | ||
| /// Simulate n input events where the i-th one is delivered at delivery_time(i). | ||
| /// | ||
| /// Simulation results will be written into events_consumed_at_frame whose | ||
| /// length will be equal to the number of frames drawn. Each element in the | ||
| /// vector is the number of input events consumed up to that frame. (We can't | ||
| /// return such vector because ASSERT_TRUE requires return type of void.) | ||
| /// | ||
| /// We assume (and check) that the delivery latency is some base latency plus a | ||
| /// random latency where the random latency must be within one frame: | ||
| /// | ||
| /// 1. latency = delivery_time(i) - j * frame_time = base_latency + | ||
| /// random_latency | ||
| /// 2. 0 <= base_latency, 0 <= random_latency < frame_time | ||
| /// | ||
| /// We also assume that there will be at least one input event per frame if | ||
| /// there were no latency. Let j = floor( (delivery_time(i) - base_latency) / | ||
| /// frame_time ) be the frame index if there were no latency. Then the set of j | ||
| /// should be all integers from 0 to continuous_frame_count - 1 for some | ||
| /// integer continuous_frame_count. | ||
| /// | ||
| /// (Note that there coulds be multiple input events within one frame.) | ||
| /// | ||
| /// The test here is insensitive to the choice of time unit as long as | ||
| /// delivery_time and frame_time are in the same unit. | ||
| static void TestSimulatedInputEvents( | ||
| ShellTest* fixture, | ||
| int num_events, | ||
| UnitlessTime base_latency, | ||
| Generator delivery_time, | ||
| UnitlessTime frame_time, | ||
| std::vector<UnitlessTime>& events_consumed_at_frame) { | ||
| ///// Begin constructing shell /////////////////////////////////////////////// | ||
| auto settings = fixture->CreateSettingsForFixture(); | ||
| std::unique_ptr<Shell> shell = fixture->CreateShell(settings); | ||
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| auto configuration = RunConfiguration::InferFromSettings(settings); | ||
| configuration.SetEntrypoint("onPointerDataPacketMain"); | ||
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| // The following 4 variables are only accessed in the UI thread by | ||
| // nativeOnPointerDataPacket and nativeOnBeginFrame between their | ||
| // initializations and `shell.reset()`. | ||
| events_consumed_at_frame.clear(); | ||
| bool will_draw_new_frame = true; | ||
| int events_consumed = 0; | ||
| int frame_drawn = 0; | ||
| auto nativeOnPointerDataPacket = [&events_consumed_at_frame, | ||
| &will_draw_new_frame, &events_consumed, | ||
| &frame_drawn](Dart_NativeArguments args) { | ||
| events_consumed += 1; | ||
| if (will_draw_new_frame) { | ||
| frame_drawn += 1; | ||
| will_draw_new_frame = false; | ||
| events_consumed_at_frame.push_back(events_consumed); | ||
| } else { | ||
| events_consumed_at_frame.back() = events_consumed; | ||
| } | ||
| }; | ||
| fixture->AddNativeCallback("NativeOnPointerDataPacket", | ||
| CREATE_NATIVE_ENTRY(nativeOnPointerDataPacket)); | ||
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| auto nativeOnBeginFrame = [&will_draw_new_frame](Dart_NativeArguments args) { | ||
| will_draw_new_frame = true; | ||
| }; | ||
| fixture->AddNativeCallback("NativeOnBeginFrame", | ||
| CREATE_NATIVE_ENTRY(nativeOnBeginFrame)); | ||
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| ASSERT_TRUE(configuration.IsValid()); | ||
| fixture->RunEngine(shell.get(), std::move(configuration)); | ||
| ///// End constructing shell ///////////////////////////////////////////////// | ||
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| ASSERT_GE(base_latency, 0); | ||
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| // Check that delivery_time satisfies our assumptions. | ||
| int continuous_frame_count = 0; | ||
| for (int i = 0; i < num_events; i += 1) { | ||
| // j is the frame index of event i if there were no latency. | ||
| int j = static_cast<int>((delivery_time(i) - base_latency) / frame_time); | ||
| if (j == continuous_frame_count) { | ||
| continuous_frame_count += 1; | ||
| } | ||
| double random_latency = delivery_time(i) - j * frame_time - base_latency; | ||
| ASSERT_GE(random_latency, 0); | ||
| ASSERT_LT(random_latency, frame_time); | ||
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| // If there were no latency, there should be at least one event per frame. | ||
| // Hence j should never skip any integer less than continuous_frame_count. | ||
| ASSERT_LT(j, continuous_frame_count); | ||
| } | ||
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| // i is the input event's index. | ||
| // j is the frame's index. | ||
| for (int i = 0, j = 0; i < num_events; j += 1) { | ||
| double t = j * frame_time; | ||
| while (i < num_events && delivery_time(i) <= t) { | ||
| ShellTest::DispatchFakePointerData(shell.get()); | ||
| i += 1; | ||
| } | ||
| ShellTest::PumpOneFrame(shell.get()); | ||
| } | ||
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| shell.reset(); | ||
| } | ||
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| TEST_F(ShellTest, MissAtMostOneFrameForIrregularInputEvents) { | ||
| // We don't use `constexpr int frame_time` here because MSVC doesn't handle | ||
| // it well with lambda capture. | ||
| UnitlessTime frame_time = 10; | ||
| UnitlessTime base_latency = 0.5 * frame_time; | ||
| Generator extreme = [frame_time, base_latency](int i) { | ||
| return static_cast<UnitlessTime>( | ||
| i * frame_time + base_latency + | ||
| (i % 2 == 0 ? 0.1 * frame_time : 0.9 * frame_time)); | ||
| }; | ||
| constexpr int n = 40; | ||
| std::vector<int> events_consumed_at_frame; | ||
| TestSimulatedInputEvents(this, n, base_latency, extreme, frame_time, | ||
| events_consumed_at_frame); | ||
| int frame_drawn = events_consumed_at_frame.size(); | ||
| ASSERT_GE(frame_drawn, n - 1); | ||
| } | ||
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| TEST_F(ShellTest, DelayAtMostOneEventForFasterThanVSyncInputEvents) { | ||
| // We don't use `constexpr int frame_time` here because MSVC doesn't handle | ||
| // it well with lambda capture. | ||
| UnitlessTime frame_time = 10; | ||
| UnitlessTime base_latency = 0.2 * frame_time; | ||
| Generator double_sampling = [frame_time, base_latency](int i) { | ||
| return static_cast<UnitlessTime>(i * 0.5 * frame_time + base_latency); | ||
| }; | ||
| constexpr int n = 40; | ||
| std::vector<int> events_consumed_at_frame; | ||
| TestSimulatedInputEvents(this, n, base_latency, double_sampling, frame_time, | ||
| events_consumed_at_frame); | ||
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| // Draw one extra frame due to delaying a pending packet for the next frame. | ||
| int frame_drawn = events_consumed_at_frame.size(); | ||
| ASSERT_EQ(frame_drawn, n / 2 + 1); | ||
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| for (int i = 0; i < n / 2; i += 1) { | ||
| ASSERT_GE(events_consumed_at_frame[i], 2 * i - 1); | ||
| } | ||
| } | ||
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| TEST_F(ShellTest, HandlesActualIphoneXsInputEvents) { | ||
| // Actual delivery times measured on iPhone Xs, in the unit of frame_time | ||
| // (16.67ms for 60Hz). | ||
| constexpr double iphone_xs_times[] = {0.15, | ||
| 1.0773046874999999, | ||
| 2.1738720703124996, | ||
| 3.0579052734374996, | ||
| 4.0890087890624995, | ||
| 5.0952685546875, | ||
| 6.1251708984375, | ||
| 7.1253076171875, | ||
| 8.125927734374999, | ||
| 9.37248046875, | ||
| 10.133950195312499, | ||
| 11.161201171875, | ||
| 12.226992187499999, | ||
| 13.1443798828125, | ||
| 14.440327148437499, | ||
| 15.091684570312498, | ||
| 16.138681640625, | ||
| 17.126469726562497, | ||
| 18.1592431640625, | ||
| 19.371372070312496, | ||
| 20.033774414062496, | ||
| 21.021782226562497, | ||
| 22.070053710937497, | ||
| 23.325541992187496, | ||
| 24.119648437499997, | ||
| 25.084262695312496, | ||
| 26.077866210937497, | ||
| 27.036547851562496, | ||
| 28.035073242187497, | ||
| 29.081411132812498, | ||
| 30.066064453124998, | ||
| 31.089360351562497, | ||
| 32.086142578125, | ||
| 33.4618798828125, | ||
| 34.14697265624999, | ||
| 35.0513525390625, | ||
| 36.136025390624994, | ||
| 37.1618408203125, | ||
| 38.144472656249995, | ||
| 39.201123046875, | ||
| 40.4339501953125, | ||
| 41.1552099609375, | ||
| 42.102128906249995, | ||
| 43.0426318359375, | ||
| 44.070131835937495, | ||
| 45.08862304687499, | ||
| 46.091469726562494}; | ||
| constexpr int n = sizeof(iphone_xs_times) / sizeof(iphone_xs_times[0]); | ||
| // We don't use `constexpr int frame_time` here because MSVC doesn't handle | ||
| // it well with lambda capture. | ||
| UnitlessTime frame_time = 10000; | ||
| for (double base_latency_f = 0; base_latency_f < 1; base_latency_f += 0.1) { | ||
| // Everything is converted to int to avoid floating point error in | ||
| // TestSimulatedInputEvents. | ||
| UnitlessTime base_latency = | ||
| static_cast<UnitlessTime>(base_latency_f * frame_time); | ||
| Generator iphone_xs_generator = [frame_time, iphone_xs_times, | ||
| base_latency](int i) { | ||
| return base_latency + | ||
| static_cast<UnitlessTime>(iphone_xs_times[i] * frame_time); | ||
| }; | ||
| std::vector<int> events_consumed_at_frame; | ||
| TestSimulatedInputEvents(this, n, base_latency, iphone_xs_generator, | ||
| frame_time, events_consumed_at_frame); | ||
| int frame_drawn = events_consumed_at_frame.size(); | ||
| ASSERT_GE(frame_drawn, n - 1); | ||
| } | ||
| } | ||
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| } // namespace testing | ||
| } // namespace flutter | ||
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There is a story of suffering behind this isn't there :)