Make FittedBox not throw when child has zero size. (#150430)

fix #135082 , fix #139539 , fix #142910 Before, `FittedBox` would throw when child size is zero, unless the constraint is tight and fit is not `BoxFit.scaleDown`.
flutter · Jul 8, 2024 · f194cd3 · f194cd3
1 parent a3c7094
commit f194cd3
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Showing 4 changed files with 49 additions and 20 deletions.
diff --git a/packages/flutter/lib/src/rendering/box.dart b/packages/flutter/lib/src/rendering/box.dart
@@ -322,10 322,12 @@ class BoxConstraints extends Constraints {
  return result;
  }
 
  if (size.isEmpty) {
  return constrain(size);
  }
 
  double width = size.width;
  double height = size.height;
- assert(width > 0.0);
- assert(height > 0.0);
  final double aspectRatio = width / height;
 
  if (width > maxWidth) {

diff --git a/packages/flutter/lib/src/rendering/proxy_box.dart b/packages/flutter/lib/src/rendering/proxy_box.dart
@@ -2711,24 2711,6 @@ class RenderFittedBox extends RenderProxyBox {
  if (child != null) {
  final Size childSize = child!.getDryLayout(const BoxConstraints());
 
- // During [RenderObject.debugCheckingIntrinsics] a child that doesn't
- // support dry layout may provide us with an invalid size that triggers
- // assertions if we try to work with it. Instead of throwing, we bail
- // out early in that case.
- bool invalidChildSize = false;
- assert(() {
- if (RenderObject.debugCheckingIntrinsics && childSize.width * childSize.height == 0.0) {
- invalidChildSize = true;
- }
- return true;
- }());
- if (invalidChildSize) {
- assert(debugCannotComputeDryLayout(
- reason: 'Child provided invalid size of $childSize.',
- ));
- return Size.zero;
- }
-
  switch (fit) {
  case BoxFit.scaleDown:
  final BoxConstraints sizeConstraints = constraints.loosen();

diff --git a/packages/flutter/test/rendering/box_constraints_test.dart b/packages/flutter/test/rendering/box_constraints_test.dart
@@ -182,4 182,17 @@ void main() {
  expect(constraints, const BoxConstraints(minWidth: 1, maxWidth: 2, minHeight: 3, maxHeight: 4));
  });
 
  test('BoxConstraints.constrainSizeAndAttemptToPreserveAspectRatio can handle empty size', () {
  const BoxConstraints constraints = BoxConstraints(
  minWidth: 10.0,
  maxWidth: 20.0,
  minHeight: 10.0,
  maxHeight: 20.0,
  );
  const Size unconstrainedSize = Size(15.0, 0.0);
  final Size constrainedSize = constraints.constrainSizeAndAttemptToPreserveAspectRatio(
  unconstrainedSize,
  );
  expect(constrainedSize, const Size(15.0, 10.0));
  });
 }
diff --git a/packages/flutter/test/widgets/fitted_box_test.dart b/packages/flutter/test/widgets/fitted_box_test.dart
@@ -605,6 605,38 @@ void main() {
  await tester.tap(find.byType(FittedBox), warnIfMissed: false);
  expect(tester.takeException(), isNull);
  });
 
  // Regression test for https://github.com/flutter/flutter/issues/135082
  testWidgets('FittedBox with zero size child does not throw', (WidgetTester tester) async {
  await tester.pumpWidget(
  const Center(
  child: SizedBox(
  height: 200.0,
  width: 200.0,
  child: FittedBox(
  fit: BoxFit.scaleDown,
  child: SizedBox.shrink(),
  ),
  ),
  ),
  );
  expect(tester.takeException(), isNull);
 
  await tester.pumpWidget(
  Center(
  child: ConstrainedBox(
  constraints: const BoxConstraints(
  maxWidth: 200.0,
  maxHeight: 200.0,
  ),
  child: const FittedBox(
  child: SizedBox.shrink(),
  ),
  ),
  ),
  );
  expect(tester.takeException(), isNull);
  });
 }
 
 List<Type> getLayers() {