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Fix FlutterPlatformViewSemanticsContainer retain cycle with SemanticsObject #24308

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Feb 9, 2021
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Fix FlutterPlatformViewSemanticsContainer retain cycle with SemanticsObject #24308

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bbdf521
fix
Feb 9, 2021
609359a
tests
Feb 9, 2021
ae15ce7
format
Feb 9, 2021
57697ad
remove testing code
Feb 9, 2021
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31 changes: 29 additions & 2 deletions shell/platform/darwin/ios/framework/Source/SemanticsObject.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -571,15 +571,42 @@ - (instancetype)initWithSemanticsObject:(SemanticsObject*)object {
}

- (void)dealloc {
[_semanticsObject release];

@chunhtai chunhtai Feb 9, 2021 •
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if the FlutterPlatformViewSemanticsContainer does not own the semantics object, it should not release it? also the property is declared as assign, it should not increase the reference count.

@chunhtai chunhtai Feb 9, 2021

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cc @gaaclarke who is more familiar with reference counting

@cyanglaz cyanglaz Feb 9, 2021

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oops good catch! This code was there for debugging and I forgot to remove it. Removed now

_semanticsObject = nil;
[_platformView release];
_platformView = nil;
[super dealloc];
}

- (NSArray*)accessibilityElements {
return @[ _semanticsObject, _platformView ];
#pragma mark - UIAccessibilityContainer overrides

- (NSInteger)accessibilityElementCount {
// This container should only contain 2 elements:
// 1. The semantic object that represents this container.
// 2. The platform view object.
return 2;
}

- (nullable id)accessibilityElementAtIndex:(NSInteger)index {
FML_DCHECK(index < 2);
if (index == 0) {
return _semanticsObject;
} else {
return _platformView;
}
}

- (NSInteger)indexOfAccessibilityElement:(id)element {
FML_DCHECK(element == _semanticsObject || element == _platformView);
if (element == _semanticsObject) {
return 0;
} else {
return 1;
}
}

#pragma mark - UIAccessibilityElement overrides

- (CGRect)accessibilityFrame {
return _semanticsObject.accessibilityFrame;
}
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12 changes: 12 additions & 0 deletions shell/platform/darwin/ios/framework/Source/SemanticsObjectTest.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -217,4 +217,16 @@ - (void)testShouldDispatchShowOnScreenActionForHidden {
XCTAssertTrue(bridge->observations[0].action == flutter::SemanticsAction::kShowOnScreen);
}

- (void)testSemanticsObjectAndPlatformViewSemanticsContainerDontHaveRetainCycle {
fml::WeakPtrFactory<flutter::MockAccessibilityBridge> factory(
new flutter::MockAccessibilityBridge());
fml::WeakPtr<flutter::MockAccessibilityBridge> bridge = factory.GetWeakPtr();
SemanticsObject* object = [[SemanticsObject alloc] initWithBridge:bridge uid:1];
object.platformViewSemanticsContainer =
[[FlutterPlatformViewSemanticsContainer alloc] initWithSemanticsObject:object];
__weak SemanticsObject* weakObject = object;
object = nil;
XCTAssertNil(weakObject);
}

@end