Fix the RenderFlex.computeDryBaseline implementation to match compute…

…DistanceToActualBaseline (#149062) Per Hixie's comment [here](#145739 (comment)), keep the current behavior
flutter · May 28, 2024 · 0214afb · 0214afb
1 parent c109b3c
commit 0214afb
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Showing 2 changed files with 58 additions and 5 deletions.
diff --git a/packages/flutter/lib/src/rendering/flex.dart b/packages/flutter/lib/src/rendering/flex.dart
@@ -308,6 308,8 @@ enum CrossAxisAlignment {
  /// See also:
  ///
  /// * [RenderBox.getDistanceToBaseline], which defines the baseline of a box.
  /// * [IgnoreBaseline], which can be used to ignore a child for the purpose of
  /// baseline alignment.
  baseline;
 
  double _getChildCrossAxisOffset(double freeSpace, bool flipped) {
@@ -821,13 823,17 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
  final double freeSpace = math.max(0.0, sizes.mainAxisFreeSpace);
  final bool flipMainAxis = _flipMainAxis;
  final (double leadingSpaceY, double spaceBetween) = mainAxisAlignment._distributeSpace(freeSpace, childCount, flipMainAxis);
- double y = leadingSpaceY;
- final (_NextChild nextChild, RenderBox? topLeftChild) = flipMainAxis ? (childBefore, lastChild) : (childAfter, firstChild);
- for (RenderBox? child = topLeftChild; child != null; child = nextChild(child)) {
  double y = flipMainAxis
  ? leadingSpaceY   (childCount - 1) * spaceBetween   (sizes.axisSize.mainAxisExtent - sizes.mainAxisFreeSpace)
  : leadingSpaceY;
  final double directionUnit = flipMainAxis ? -1.0 : 1.0;
  for (RenderBox? child = firstChild; baselineOffset == BaselineOffset.noBaseline && child != null; child = childAfter(child)) {
  final BoxConstraints childConstraints = constraintsForChild(child);
  final Size childSize = child.getDryLayout(childConstraints);
- baselineOffset = baselineOffset.minOf(BaselineOffset(child.getDryBaseline(childConstraints, baseline))   y);
- y  = spaceBetween   childSize.height;
  final double? childBaselineOffset = child.getDryBaseline(childConstraints, baseline);
  final double additionalY = flipMainAxis ? - childSize.height : 0.0;
  baselineOffset = BaselineOffset(childBaselineOffset)   y   additionalY;
  y  = directionUnit * (spaceBetween   childSize.height);
  }
  case Axis.horizontal:
  final bool flipCrossAxis = _flipCrossAxis;

diff --git a/packages/flutter/test/rendering/flex_test.dart b/packages/flutter/test/rendering/flex_test.dart
@@ -648,6 648,53 @@ void main() {
  expect(box2.localToGlobal(Offset.zero).dy, 0.0);
  });
 
  test('Vertical Flex Baseline', () {
  const BoxConstraints square = BoxConstraints.tightFor(width: 100.0, height: 100.0);
  final RenderConstrainedBox box1 = RenderConstrainedBox(
  additionalConstraints: square,
  child: RenderFlowBaselineTestBox()
  ..gridCount = 1
  ..baselinePlacer = (double height) => 10,
  );
  final RenderConstrainedBox box2 = RenderConstrainedBox(
  additionalConstraints: square,
  child: RenderFlowBaselineTestBox()
  ..gridCount = 1
  ..baselinePlacer = (double height) => 10,
  );
  RenderConstrainedBox filler() => RenderConstrainedBox(additionalConstraints: square);
  final RenderFlex flex = RenderFlex(
  textDirection: TextDirection.ltr,
  children: <RenderBox>[
  filler(),
  box1,
  filler(),
  box2,
  filler(),
  ],
  direction: Axis.vertical,
  );
  layout(flex, phase: EnginePhase.paint);
  final double flexHeight = flex.size.height;
 
  // We can't call the getDistanceToBaseline method directly. Check the dry
  // baseline instead, and in debug mode there are asserts that verify
  // the two methods return the same results.
  expect(flex.getDryBaseline(flex.constraints, TextBaseline.alphabetic), 100   10);
 
  flex.mainAxisAlignment = MainAxisAlignment.end;
  pumpFrame(phase: EnginePhase.paint);
  expect(flex.getDryBaseline(flex.constraints, TextBaseline.alphabetic), flexHeight - 400   10);
 
  flex.verticalDirection = VerticalDirection.up;
  pumpFrame(phase: EnginePhase.paint);
  expect(flex.getDryBaseline(flex.constraints, TextBaseline.alphabetic), 300   10);
 
  flex.mainAxisAlignment = MainAxisAlignment.start;
  pumpFrame(phase: EnginePhase.paint);
  expect(flex.getDryBaseline(flex.constraints, TextBaseline.alphabetic), flexHeight - 200   10);
  });
 
  group('Intrinsics', () {
  test('main axis intrinsics with RenderAspectRatio 1', () {
  const BoxConstraints square = BoxConstraints.tightFor(width: 100.0, height: 100.0);