Added computeDryBaseline implementation in RenderAligningShiftedBox #171250

lewinpauli · 2025-06-26T23:53:24Z

Implements computeDryBaseline method in RenderAligningShiftedBox to fix layout failures when DropdownButtonFormField is used inside Wrap inside AlertDialog. The method calculates baseline using dry layout methods and accounts for child positioning within the parent's coordinate space.

Issue appeared when DropdownButtonFormField was used inside a Wrap inside Alertdialog

Fixes flutter/flutter/issues/169214

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I signed the CLA.
I listed at least one issue that this PR fixes in the description above.
I updated/added relevant documentation (doc comments with ///).
I added new tests to check the change I am making, or this PR is test-exempt.
I followed the breaking change policy and added Data Driven Fixes where supported.
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Implements computeDryBaseline method in RenderShiftedBox to fix layout failures when DropdownButtonFormField is used inside Wrap inside AlertDialog. The method calculates baseline using dry layout methods and accounts for child positioning within the parent's coordinate space. Fixes flutter/issues/169214

flutter-dashboard · 2025-06-26T23:53:27Z

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

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justinmc · 2025-07-08T22:24:18Z

Thanks for opening a PR for this! Would you be able to add a test? Ideally something that reproduces the issue in #169214 and shows that it no longer happens with this change.

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lewinpauli · 2025-07-29T14:16:31Z

@justinmc while creating tests i came across that "RenderSizedBox" has not implemented method "computeDryBaseline" either, but i don't have a deep flutter framework understanding so i don't know if this is a bug

test('computeDryBaseline returns null when child has no baseline', () {
      final RenderSizedBox child = RenderSizedBox(const Size(50.0, 50.0));
      final RenderPadding padding = RenderPadding(
        padding: const EdgeInsets.all(10.0),
        child: child,
      );

      final double? baseline = padding.computeDryBaseline(
        const BoxConstraints(maxWidth: 100.0, maxHeight: 100.0),
        TextBaseline.alphabetic,
      );

      expect(baseline, isNull);
    });

The RenderSizedBox class does not implement "computeDryBaseline".
If you are not writing your own RenderBox subclass, then this is not
your fault. Contact support: https://github.com/flutter/flutter/issues/new?template=02_bug.yml
package:flutter/src/rendering/box.dart 2229:9          RenderBox.debugCannotComputeDryLayout.<fn>
package:flutter/src/rendering/box.dart 2233:6          RenderBox.debugCannotComputeDryLayout
package:flutter/src/rendering/box.dart 2184:7          RenderBox.computeDryBaseline
package:flutter/src/rendering/box.dart 2140:50         RenderBox._computeDryBaseline
package:flutter/src/rendering/box.dart 1088:42         _Baseline.memoize.ifAbsent
dart:_compact_hash                                     _LinkedHashMapMixin.putIfAbsent
package:flutter/src/rendering/box.dart 1089:18         _Baseline.memoize
package:flutter/src/rendering/box.dart 1620:32         RenderBox._computeWithTimeline
package:flutter/src/rendering/box.dart 1598:26         RenderBox._computeIntrinsics
package:flutter/src/rendering/box.dart 2118:36         RenderBox.getDryBaseline
package:flutter/src/rendering/shifted_box.dart 255:30  RenderPadding.computeDryBaseline
test/rendering/shifted_box_test.dart 52:40             main.<fn>.<fn>
shifted_box_test.dart:52
✖ RenderShiftedBox computeDryBaseline returns null when child has no baseline

…teDryBaseline in RenderShiftedBox

…est/app_test.dart to check if issue 169214 still occurs

…eded switch case

lewinpauli · 2025-07-30T11:06:33Z

@justinmc how can i add a checksum in my pubspec.yaml, that is needed for my integration test. Which algorithm/command is used?

(most of the tests in CI/CD are failing because the checksum does not exist)

locally integration test reproduces the flutter error flutter/flutter/issues/169214 and ensures its working

name: alert_dialog_dropdown_crash
description: An integration test to reproduce AlertDialog with DropdownButton crash.
environment:
  sdk: ^3.8.0-0

# resolution: workspace

dependencies:
  flutter:
    sdk: flutter
  integration_test:
    sdk: flutter
  flutter_test:
    sdk: flutter
  test: any

  meta: any

flutter:
  uses-material-design: true

# PUBSPEC CHECKSUM: ?????

…igningShiftedBox for issue 169214

justinmc

Maybe you don't need an integration test at all?

I'm still curious about the checksum though. I actually don't know how those are generated off the top of my head. I'll look for an answer either way.

Edit: I believe you need to run flutter update-packages --update-hashes to update that checksum. Thanks to @jason-simmons for helping me out with that.

dev/integration_tests/alert_dialog_dropdown_crash/integration_test/app_test.dart

…eate # PUBSPEC CHECKSUM: (yes it does)

…st/material/dropdown_dialog_baseline_test.dart and update computeDryBaseline in RenderAligningShiftedBox to prevent crashes with DropdownButton in AlertDialog

lewinpauli · 2025-08-10T08:29:09Z

@justinmc I added missing computeDryBaseline in RenderAlignedShiftedBox

also now a unittest exists: packages/flutter/test/rendering/shifted_box_test.dart

and I replaced the integration test with a much less ressource intensive widget test: packages/flutter/test/rendering/aligning_shifted_box_baseline_test.dart

to verify computeDryBaseline in RenderAlignedShiftedBox exists, and the widget test reproduces the issue in #169214

… to aligning_shifted_box_baseline_test.dart

…puteDryBaseline tests

…eline Resolved merge conflicts in packages/flutter/lib/src/semantics/binding.dart Removed semantics_binding_set_semantics_tree_enabled_test.dart (deleted upstream)

lewinpauli · 2025-08-27T09:09:20Z

To provide some context, I originally wanted to fix an issue that appeared when a DropdownButtonFormField was used inside a Wrap inside an AlertDialog, as described in #169214. The issue was that the implementation of the 'computeDryBaseline' function was missing in the 'RenderAligningShiftedBox' class. I added this, as well as unit and widget tests.

Quite a few tests were failing, so I had to edit some files. For example, the renderAnimatedSize also had no computeDryBaseline implementation, as did RenderShiftedBox, RenderPositionedBox and _RenderBadge.

In material/button.dart, material/button_style_button.dart and _RenderInputPadding, the Size(width, height) was mixed up.

justinmc

LGTM as long as Google tests pass. Thank you for all of the work and iterations on this. The lack of (or incorrect) dry layout calculations were probably causing headaches for a lot of users.

justinmc · 2025-10-10T04:22:51Z

packages/flutter/lib/src/material/button.dart

-      final double height = math.max(childSize.width, minSize.width);
-      final double width = math.max(childSize.height, minSize.height);
-      return constraints.constrain(Size(height, width));
+      final double width = math.max(childSize.width, minSize.width);
+      final double height = math.max(childSize.height, minSize.height);
+      return constraints.constrain(Size(width, height));


Good catch!

justinmc · 2025-10-10T04:24:22Z

packages/flutter/lib/src/material/toggle_buttons.dart

    if (result == null) {
      return null;
    }
+    // Calculate the size and child offset using the same logic as performLayout


Nit: Period at the end of this comment and a few other comments below.

justinmc · 2025-10-10T04:33:55Z

packages/flutter/lib/src/rendering/flex.dart

+    double pos = leadingSpace;
+    for (RenderBox? child = startChild; child != null; child = nextChildPaintOrder(child)) {
+      mainPositions[child] = pos;
+      final BoxConstraints cc = constraintsForChild(child);
+      final Size cs = child.getDryLayout(cc);
+      pos += _getMainSize(cs) + betweenSpace;


Avoid abbreviations per the styleguide, here and at least one more time below.

justinmc · 2025-10-10T04:39:41Z

packages/flutter/test/rendering/shifted_box_test.dart

+        TextBaseline.alphabetic,
+      );
+
+      expect(baseline, isNotNull);


What caused you to expect isNotNull here instead of the specific value?

dkwingsmt · 2025-10-15T18:18:20Z

Friendly ping @chunhtai Are you still comfortable reviewing this PR or would you like someone else to take over it? (from triage)

chunhtai

LGTM once justin's comments are addressed

auto-submit · 2025-10-29T18:12:05Z

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lewinpauli and others added 3 commits July 29, 2025 16:23

Merge branch 'master' into fix-renderShiftedBox-computeDryBaseline

b2b1d22

Added packages/flutter/test/rendering/shifted_box_test.dart for compu…

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…teDryBaseline in RenderShiftedBox

added dev/integration_tests/alert_dialog_dropdown_crash/integration_t…

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…est/app_test.dart to check if issue 169214 still occurs

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Merge branch 'master' into fix-renderShiftedBox-computeDryBaseline

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moved computeDryBaseline to RenderAligningShiftedBox to remove not ne…

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…eded switch case

lewinpauli changed the title ~~Added computeDryBaseline implementation in RenderShiftedBox~~ Added computeDryBaseline implementation in RenderAligningShiftedBox Jul 30, 2025

lewinpauli and others added 5 commits July 30, 2025 14:31

update tests to use RenderAligningShiftedBox instead of RenderShiftedBox

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fix: update print statement in integration test to reference RenderAl…

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…igningShiftedBox for issue 169214

Merge branch 'master' into fix-renderShiftedBox-computeDryBaseline

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added # PUBSPEC CHECKSUM: at the end of pubspec.yaml

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Merge branch 'master' into fix-renderShiftedBox-computeDryBaseline

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…st/material/dropdown_dialog_baseline_test.dart and update computeDryBaseline in RenderAligningShiftedBox to prevent crashes with DropdownButton in AlertDialog

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DropdownButtonFormField in Wrap inside of SliverFillRemaining with hasScrollBody=false breaks rendering #155157

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RenderPositionedBox class does not implement "computeDryBaseline" #179227

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Added computeDryBaseline implementation in RenderAligningShiftedBox #171250

Added computeDryBaseline implementation in RenderAligningShiftedBox #171250

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