[kaluli123123]

Ports flutter/flutter#191656, which is blocked by the Material/Cupertino code freeze in flutter/flutter (see flutter/flutter#188444).

Original description

GridTile placed every child of its Stack in a Positioned widget, including the tile content. A Stack without any non-positioned child sizes itself to the biggest allowed size, which is infinite along the main axis of an unbounded parent such as a horizontally scrolling ListView. RenderStack then failed its size.isFinite assertion.

The tile content is now a non-positioned child of the Stack (with StackFit.passthrough), wrapped in a small private render object that makes it fill every bounded axis of the incoming constraints and lets it pick its own size only along unbounded axes. As a result, the layout is unchanged whenever the old code did not crash (tight constraints as in GridView, and bounded but loose constraints such as Center > ConstrainedBox), including the reported intrinsic sizes, and the tile shrink-wraps its content along an unbounded axis instead of crashing.

Fixes flutter/flutter#82055

Test plan

• flutter test test/grid_title_test.dart
• flutter test
• flutter analyze
• dart format --output=none --set-exit-if-changed packages/material_ui/lib/src/grid_tile.dart packages/material_ui/test/grid_title_test.dart

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

The change uses the repository's pending changelog workflow (packages/material_ui/pending_changelogs/change_2026_08_25_port191656.yaml). No public API documentation change is needed.

Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩²

[gemini-code-assist]

Code Review

This pull request updates GridTile to size itself to its child when incoming constraints are unbounded, such as inside a horizontally scrolling ListView. This is implemented by setting fit: StackFit.passthrough on the Stack and removing the Positioned.fill wrapper from the child. The changes also include regression tests to verify behavior under both unconstrained and tight constraints, along with a pending changelog entry. There are no review comments, and no additional feedback is provided.

[Piinks]

Hi @kaluli123123 thanks for porting over. Because of the volume of PRs we receive, we require that contributors use our checklist to guide them through critical steps in creating a Flutter PR. This PR's description is missing that checklist, so it is being marked as a Draft.

Please edit the PR description to add the checklist, then ensure that you have completed all of the steps. Once you've done that, please mark the PR as ready for review.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

Also note, PRs in this repo need to be prepended with the package name they are changing, as in .. "[material_ui] "

[gemini-code-assist]

Code Review

This pull request updates GridTile to size itself to its child when incoming constraints are unbounded (such as in a horizontally scrolling ListView) by setting fit: StackFit.passthrough on the Stack and removing Positioned.fill from the child. It also adds corresponding regression and behavior tests, along with a pending changelog entry. There are no review comments, so I have no feedback to provide.

[QuncCccccc]

Thanks for porting this! The crash fix makes sense, but I have a concern about backward compatibility.

This changes layout behavior whenever the incoming constraints aren't tight. I verified locally:

Center(
  child: ConstrainedBox(
    constraints: const BoxConstraints(maxWidth: 200, maxHeight: 150),
    child: GridTile(
      header: Text('Header'),
      footer: Text('Footer'),
      child: Container(width: 80, height: 100, color: Colors.red),
    ),
  ),
)

Before: GridTile size = Size(200, 150) — the child expanded via Positioned.fill
After: GridTile size = Size(80, 100) — the child shrink-wraps via StackFit.passthrough
The two new tests only cover tight and unbounded constraints, so this case isn't caught. Since GridTile can be used outside GridView (e.g. in Center, Align, Column, Wrap), this could be a visible layout change for existing apps.

Curious about your thoughts.

[kaluli123123]

@QuncCccccc Thanks for catching this, you are right that the previous version changed the layout for bounded but loose constraints.

I pushed 68b5150, which limits the behavior change to the case that used to crash:

• The tile content is still a non-positioned child of the Stack (with StackFit.passthrough), but it is now wrapped in a small private render object that tightens every bounded axis of the incoming constraints to its max. So the child fills the tile exactly as it did with Positioned.fill, and it only picks its own size along an unbounded axis.
• The wrapper also reports zero intrinsic sizes, which matches what the tile reported before (the Stack ignored the positioned child for intrinsics).

Evidence (all measured locally, Flutter 3.44.7):

• Your example (Center > ConstrainedBox(maxWidth: 200, maxHeight: 150) > GridTile with header/footer and an 80x100 child), added as the new test GridTile child fills the tile when the constraints are bounded but loose:
  • main: tile Size(200.0, 150.0), child Size(200.0, 150.0) (test passes)
  • previous head d4b1142: tile Size(80.0, 100.0) (test fails)
  • new head: tile Size(200.0, 150.0), child Size(200.0, 150.0) (test passes)
• Intrinsics / dry layout (same tile inside IntrinsicWidth, one-off probe, not committed): main and the new head both report min/max intrinsic width/height 0.0, dry layout Size(200.0, 150.0) for maxWidth: 200, maxHeight: 150, and the same laid out size. The previous head reported 80.0/100.0 and Size(80.0, 100.0).
• The horizontal ListView regression test still passes with the tile at Size(80.0, 100.0) and no exception (it fails on main with the RenderStack size.isFinite assertion). The tight-constraints test still passes.
• flutter test test/grid_title_test.dart: 6/6 passed. Full flutter test for material_ui: all tests passed (+8138, ~11 skipped).
• dart run script/tool/bin/flutter_plugin_tools.dart analyze --packages material_ui: No issues found. dart format --set-exit-if-changed on the changed files: 0 changed.

I also updated the PR description to reflect the new approach.

[elliette]

LGTM with a few testing suggestions. Thank you!

[elliette]

Since reporting zero intrinsics is deliberate it would be nice to have a small test for it so a future refactor doesn't change it by accident.

[elliette]

Nit: since only the width is unbounded here, maybe change "when unconstrained" to "when the width is unbounded".

[QuncCccccc]

Thanks a lot for the fix! LGTM once the comment below and the comment to add a unit test https://github.com/flutter/packages/pull/12586/changes#r4159616084 are fixed:)

[QuncCccccc]

getDryLayout now asks the child, and main didn't. So for a tile with a header or footer whose child can't compute a dry layout (for example a LayoutBuilder), getDryLayout now throws instead of returning the full size of the constraints, as main does. This is rare (a GridView never asks for a dry layout), but when both axes are bounded the size is already known, so returning early in computeDryLayout would keep the old behavior:

Suggested change

	return constraints.constrain(
	if (childConstraints.isTight) {
	return childConstraints.smallest;
	}
	return constraints.constrain(

[kaluli123123]

Fixed in 0f5a19a. computeDryLayout now returns the known size immediately when filling the bounded axes produces tight constraints, without asking the child for dry layout. Unbounded axes still use the child's dry size.

Added a regression with a LayoutBuilder child and both loose bounded and tight constraints. Before the fix it fails with _RenderLayoutBuilder class does not support dry layout; after the fix it passes. Also added all four zero-intrinsic assertions and renamed the existing regression to specify that only the width is unbounded.

Verification with Flutter 3.47.0 / Dart 3.13:

• flutter test test/grid_title_test.dart: 9 passed.
• Full material_ui suite: 8,227 passed, 12 skipped.
• Repository analyze, validate --base-branch origin/main, publish-check, and license-check passed. The publish dry-run reports an informational hint that this branch's batched version predates the latest published version.
• Changed-file formatting and git diff --check passed.

These are local results; current-head CI and maintainer review remain separate gates.