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[rotation_distortion] Use "delayed swap" solution to reduce rotation distortion #40730

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Apr 17, 2023
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[rotation_distortion] Use "delayed swap" solution to reduce rotation distortion #40730

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09e4dc1
[rotation_distortion]delayed swap to reduce rotation distortion
hellohuanlin Mar 27, 2023
ba8828f
use mainScreenIfViewLoaded
hellohuanlin Mar 29, 2023
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82 changes: 67 additions & 15 deletions shell/platform/darwin/ios/framework/Source/FlutterViewController.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,11 @@ @interface FlutterViewController () <FlutterBinaryMessenger, UIScrollViewDelegat
@property(nonatomic, assign) BOOL isHomeIndicatorHidden;
@property(nonatomic, assign) BOOL isPresentingViewControllerAnimating;

/**
* Whether we should ignore viewport metrics updates during rotation transition.
*/
@property(nonatomic, assign) BOOL shouldIgnoreViewportMetricsUpdatesDuringRotation;

/**
* Keyboard animation properties
*/
Expand Down Expand Up @@ -837,6 +842,35 @@ - (void)viewDidDisappear:(BOOL)animated {
[super viewDidDisappear:animated];
}

- (void)viewWillTransitionToSize:(CGSize)size
withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
[super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];

// We delay the viewport metrics update for half of rotation transition duration, to address
// a bug with distorted aspect ratio.
// See: https://github.com/flutter/flutter/issues/16322
//
// This approach does not fully resolve all distortion problem. But instead, it reduces the
// rotation distortion roughly from 4x to 2x. The most distorted frames occur in the middle
// of the transition when it is rotating the fastest, making it hard to notice.

NSTimeInterval transitionDuration = coordinator.transitionDuration;
// Do not delay viewport metrics update if zero transition duration.
if (transitionDuration == 0) {
return;
}

_shouldIgnoreViewportMetricsUpdatesDuringRotation = YES;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW,
static_cast<int64_t>(transitionDuration / 2.0 * NSEC_PER_SEC)),
dispatch_get_main_queue(), ^{
// `viewWillTransitionToSize` is only called after the previous rotation is
// complete. So there won't be race condition for this flag.
_shouldIgnoreViewportMetricsUpdatesDuringRotation = NO;
[self updateViewportMetricsIfNeeded];
});
}

- (void)flushOngoingTouches {
if (_engine && _ongoingTouches.get().count > 0) {
auto packet = std::make_unique<flutter::PointerDataPacket>(_ongoingTouches.get().count);
Expand Down Expand Up @@ -1226,7 +1260,10 @@ - (void)invalidateTouchRateCorrectionVSyncClient {

#pragma mark - Handle view resizing

- (void)updateViewportMetrics {
- (void)updateViewportMetricsIfNeeded {
if (_shouldIgnoreViewportMetricsUpdatesDuringRotation) {
return;
}
if ([_engine.get() viewController] == self) {
[_engine.get() updateViewportMetrics:_viewportMetrics];
}
Expand All @@ -1243,11 +1280,9 @@ - (void)viewDidLayoutSubviews {
// First time since creation that the dimensions of its view is known.
bool firstViewBoundsUpdate = !_viewportMetrics.physical_width;
_viewportMetrics.device_pixel_ratio = scale;
_viewportMetrics.physical_width = viewBounds.size.width * scale;
_viewportMetrics.physical_height = viewBounds.size.height * scale;

[self updateViewportPadding];
[self updateViewportMetrics];
[self setViewportMetricsSize];
[self setViewportMetricsPaddings];
[self updateViewportMetricsIfNeeded];

// There is no guarantee that UIKit will layout subviews when the application is active. Creating
// the surface when inactive will cause GPU accesses from the background. Only wait for the first
Expand Down Expand Up @@ -1276,16 +1311,33 @@ - (void)viewDidLayoutSubviews {
}

- (void)viewSafeAreaInsetsDidChange {
[self updateViewportPadding];
[self updateViewportMetrics];
[self setViewportMetricsPaddings];
[self updateViewportMetricsIfNeeded];
[super viewSafeAreaInsetsDidChange];
}

// Updates _viewportMetrics physical padding.
// Set _viewportMetrics physical size.
- (void)setViewportMetricsSize {
UIScreen* mainScreen = [self mainScreenIfViewLoaded];
if (!mainScreen) {
return;
}

CGFloat scale = mainScreen.scale;
_viewportMetrics.physical_width = self.view.bounds.size.width * scale;
_viewportMetrics.physical_height = self.view.bounds.size.height * scale;
}

// Set _viewportMetrics physical paddings.
//
// Viewport padding represents the iOS safe area insets.
- (void)updateViewportPadding {
CGFloat scale = [UIScreen mainScreen].scale;
// Viewport paddings represent the iOS safe area insets.
- (void)setViewportMetricsPaddings {
UIScreen* mainScreen = [self mainScreenIfViewLoaded];
if (!mainScreen) {
return;
}

CGFloat scale = mainScreen.scale;
_viewportMetrics.physical_padding_top = self.view.safeAreaInsets.top * scale;
_viewportMetrics.physical_padding_left = self.view.safeAreaInsets.left * scale;
_viewportMetrics.physical_padding_right = self.view.safeAreaInsets.right * scale;
Expand Down Expand Up @@ -1609,15 +1661,15 @@ - (void)setupKeyboardAnimationVsyncClient {
flutterViewController.get()->_viewportMetrics.physical_view_inset_bottom =
flutterViewController.get()
.keyboardAnimationView.layer.presentationLayer.frame.origin.y;
[flutterViewController updateViewportMetrics];
[flutterViewController updateViewportMetricsIfNeeded];
}
} else {
fml::TimeDelta timeElapsed = recorder.get()->GetVsyncTargetTime() -
flutterViewController.get().keyboardAnimationStartTime;

flutterViewController.get()->_viewportMetrics.physical_view_inset_bottom =
[[flutterViewController keyboardSpringAnimation] curveFunction:timeElapsed.ToSecondsF()];
[flutterViewController updateViewportMetrics];
[flutterViewController updateViewportMetricsIfNeeded];
}
};
flutter::Shell& shell = [_engine.get() shell];
Expand Down Expand Up @@ -1646,7 +1698,7 @@ - (void)ensureViewportMetricsIsCorrect {
if (_viewportMetrics.physical_view_inset_bottom != self.targetViewInsetBottom) {
// Make sure the `physical_view_inset_bottom` is the target value.
_viewportMetrics.physical_view_inset_bottom = self.targetViewInsetBottom;
[self updateViewportMetrics];
[self updateViewportMetricsIfNeeded];
}
}

Expand Down
88 changes: 83 additions & 5 deletions shell/platform/darwin/ios/framework/Source/FlutterViewControllerTest.mm
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -124,7 +124,7 @@ - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences;
- (void)handlePressEvent:(FlutterUIPressProxy*)press
nextAction:(void (^)())next API_AVAILABLE(ios(13.4));
- (void)discreteScrollEvent:(UIPanGestureRecognizer*)recognizer;
- (void)updateViewportMetrics;
- (void)updateViewportMetricsIfNeeded;
- (void)onUserSettingsChanged:(NSNotification*)notification;
- (void)applicationWillTerminate:(NSNotification*)notification;
- (void)goToApplicationLifecycle:(nonnull NSString*)state;
Expand Down Expand Up @@ -834,7 +834,7 @@ - (void)testViewDidDisappearDoesPauseEngineWhenIsTheViewController {
OCMReject([lifecycleChannel sendMessage:@"AppLifecycleState.inactive"]);
}

- (void)testUpdateViewportMetricsDoesntInvokeEngineWhenNotTheViewController {
- (void)testUpdateViewportMetricsIfNeeded_DoesntInvokeEngineWhenNotTheViewController {
FlutterEngine* mockEngine = OCMPartialMock([[FlutterEngine alloc] init]);
[mockEngine createShell:@"" libraryURI:@"" initialRoute:nil];
FlutterViewController* viewControllerA = [[FlutterViewController alloc] initWithEngine:mockEngine
Expand All @@ -845,12 +845,12 @@ - (void)testUpdateViewportMetricsDoesntInvokeEngineWhenNotTheViewController {
nibName:nil
bundle:nil];
mockEngine.viewController = viewControllerB;
[viewControllerA updateViewportMetrics];
[viewControllerA updateViewportMetricsIfNeeded];
flutter::ViewportMetrics viewportMetrics;
OCMVerify(never(), [mockEngine updateViewportMetrics:viewportMetrics]);
}

- (void)testUpdateViewportMetricsDoesInvokeEngineWhenIsTheViewController {
- (void)testUpdateViewportMetricsIfNeeded_DoesInvokeEngineWhenIsTheViewController {
FlutterEngine* mockEngine = OCMPartialMock([[FlutterEngine alloc] init]);
[mockEngine createShell:@"" libraryURI:@"" initialRoute:nil];
FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:mockEngine
Expand All @@ -859,7 +859,85 @@ - (void)testUpdateViewportMetricsDoesInvokeEngineWhenIsTheViewController {
mockEngine.viewController = viewController;
flutter::ViewportMetrics viewportMetrics;
OCMExpect([mockEngine updateViewportMetrics:viewportMetrics]).ignoringNonObjectArgs();
[viewController updateViewportMetrics];
[viewController updateViewportMetricsIfNeeded];
OCMVerifyAll(mockEngine);
}

- (void)testUpdateViewportMetricsIfNeeded_DoesNotInvokeEngineWhenShouldBeIgnoredDuringRotation {
FlutterEngine* mockEngine = OCMPartialMock([[FlutterEngine alloc] init]);
[mockEngine createShell:@"" libraryURI:@"" initialRoute:nil];
FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:mockEngine
nibName:nil
bundle:nil];
FlutterViewController* viewControllerMock = OCMPartialMock(viewController);
OCMStub([viewControllerMock mainScreenIfViewLoaded]).andReturn(UIScreen.mainScreen);
mockEngine.viewController = viewController;

id mockCoordinator = OCMProtocolMock(@protocol(UIViewControllerTransitionCoordinator));
OCMStub([mockCoordinator transitionDuration]).andReturn(0.5);

// Mimic the device rotation.
[viewController viewWillTransitionToSize:CGSizeZero withTransitionCoordinator:mockCoordinator];
// Should not trigger the engine call when during rotation.
[viewController updateViewportMetricsIfNeeded];

OCMVerify(never(), [mockEngine updateViewportMetrics:flutter::ViewportMetrics()]);
}

- (void)testViewWillTransitionToSize_DoesDelayEngineCallIfNonZeroDuration {
FlutterEngine* mockEngine = OCMPartialMock([[FlutterEngine alloc] init]);
[mockEngine createShell:@"" libraryURI:@"" initialRoute:nil];
FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:mockEngine
nibName:nil
bundle:nil];
FlutterViewController* viewControllerMock = OCMPartialMock(viewController);
OCMStub([viewControllerMock mainScreenIfViewLoaded]).andReturn(UIScreen.mainScreen);
mockEngine.viewController = viewController;

// Mimic the device rotation with non-zero transition duration.
NSTimeInterval transitionDuration = 0.5;
id mockCoordinator = OCMProtocolMock(@protocol(UIViewControllerTransitionCoordinator));
OCMStub([mockCoordinator transitionDuration]).andReturn(transitionDuration);

flutter::ViewportMetrics viewportMetrics;
OCMExpect([mockEngine updateViewportMetrics:viewportMetrics]).ignoringNonObjectArgs();

[viewController viewWillTransitionToSize:CGSizeZero withTransitionCoordinator:mockCoordinator];
// Should not immediately call the engine (this request should be ignored).
[viewController updateViewportMetricsIfNeeded];
OCMVerify(never(), [mockEngine updateViewportMetrics:flutter::ViewportMetrics()]);

// Should delay the engine call for half of the transition duration.
// Wait for additional transitionDuration to allow updateViewportMetrics calls if any.
XCTWaiterResult result = [XCTWaiter
waitForExpectations:@[ [self expectationWithDescription:@"Waiting for rotation duration"] ]
timeout:transitionDuration];
XCTAssertEqual(result, XCTWaiterResultTimedOut);

OCMVerifyAll(mockEngine);
}

- (void)testViewWillTransitionToSize_DoesNotDelayEngineCallIfZeroDuration {
FlutterEngine* mockEngine = OCMPartialMock([[FlutterEngine alloc] init]);
[mockEngine createShell:@"" libraryURI:@"" initialRoute:nil];
FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:mockEngine
nibName:nil
bundle:nil];
FlutterViewController* viewControllerMock = OCMPartialMock(viewController);
OCMStub([viewControllerMock mainScreenIfViewLoaded]).andReturn(UIScreen.mainScreen);
mockEngine.viewController = viewController;

// Mimic the device rotation with zero transition duration.
id mockCoordinator = OCMProtocolMock(@protocol(UIViewControllerTransitionCoordinator));
OCMStub([mockCoordinator transitionDuration]).andReturn(0);

flutter::ViewportMetrics viewportMetrics;
OCMExpect([mockEngine updateViewportMetrics:viewportMetrics]).ignoringNonObjectArgs();

// Should immediately trigger the engine call, without delay.
[viewController viewWillTransitionToSize:CGSizeZero withTransitionCoordinator:mockCoordinator];
[viewController updateViewportMetricsIfNeeded];

OCMVerifyAll(mockEngine);
}

Expand Down