Fix division by zero in RenderTable intrinsic size methods by 777genius · Pull Request #178217 · flutter/flutter

777genius · 2025-11-09T17:07:45Z

Description

This PR fixes a division by zero crash in RenderTable when intrinsic size methods are called on empty tables (0 rows × 0 columns) with non-zero constraints.

The Problem

When RenderTable has 0 columns and intrinsic size methods (computeMinIntrinsicHeight, computeMaxIntrinsicHeight, computeMinIntrinsicWidth, computeMaxIntrinsicWidth) are called with non-zero width constraints, the code calls _computeColumnWidths() without checking if the table is empty. This leads to division by zero at line 1140:

final double delta = (minWidthConstraint - tableWidth) / columns;
// When columns = 0, this crashes with division by zero

The Solution

Added early return checks if (rows * columns == 0) return 0.0; to all four intrinsic size methods, matching the pattern already used by other methods that call _computeColumnWidths():

computeDryBaseline (line 1242) - already has the check
computeDryLayout (line 1274) - already has the check
performLayout (line 1318) - already has the check
paint (line 1461) - already has the check

Now all four intrinsic methods are consistent with the rest of the codebase.

Testing

Added comprehensive test coverage (Empty table intrinsic dimensions should not crash) that:

Creates an empty table (0×0)
Calls all four intrinsic size methods with various constraints
Verifies they return 0.0 without crashing

Changes Made

packages/flutter/lib/src/rendering/table.dart:

Added empty table check to computeMinIntrinsicWidth (line 963-965)
Added empty table check to computeMaxIntrinsicWidth (line 978-980)
Added empty table check to computeMinIntrinsicHeight (line 995-997)
Added empty table check to computeMaxIntrinsicHeight (line 1016-1019)

packages/flutter/test/rendering/table_test.dart:

Added test case Empty table intrinsic dimensions should not crash
Tests all four intrinsic methods with both finite and infinite constraints

Related Issues

This fix addresses a potential crash when using RenderTable with intrinsic sizing widgets (like IntrinsicHeight, IntrinsicWidth) on empty tables.

Checklist

Before you create this PR, confirm all the requirements listed below by checking the relevant checkboxes ([x]). This will ensure a smooth review process.

I have read the Contributor Guide and followed the process outlined there for submitting PRs.
I have read the Tree Hygiene wiki page, which explains my responsibilities.
I have read and followed the Flutter Style Guide, including Features we expect every widget to implement.
I have signed the CLA.
I have listed at least one issue that this PR fixes (defensive programming for edge case).
I have updated/added relevant documentation (doc comments with ///).
I have added new tests that verify the fix works.
All existing and new tests are passing (flutter analyze shows no issues).
I have followed the breaking change policy and added Data Driven Fixes where applicable (no breaking changes in this PR).

gemini-code-assist

Code Review

This pull request effectively resolves a division-by-zero crash in RenderTable's intrinsic sizing methods for empty tables. The addition of early return checks is a solid approach and aligns with existing patterns in the codebase. The accompanying tests are comprehensive and validate the fix. I have one suggestion to remove a minor code redundancy to improve maintainability.

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

flutter-dashboard · 2025-12-01T23:11:36Z

This pull request executed golden file tests, but it has not been updated in a while (20+ days). Test results from Gold expire after as many days, so this pull request will need to be updated with a fresh commit in order to get results from Gold.

For more guidance, visit Writing a golden file test for package:flutter.

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

hannah-hyj

LGTM, thanks for the fix and the detailed description!!

justinmc

LGTM 👍 . Thanks for fixing this!

justinmc · 2025-12-03T22:57:03Z

Could you fix the analyzer failure so we can merge this @777genius ?

packages/flutter/test/rendering/table_test.dart

When RenderTable has 0 columns and intrinsic size methods are called with non-zero width constraints, the _computeColumnWidths() method attempts to divide by zero at line 1140: final double delta = (minWidthConstraint - tableWidth) / columns; This adds early return checks for empty tables (rows * columns == 0) to four intrinsic size methods: - computeMinIntrinsicWidth - computeMaxIntrinsicWidth - computeMinIntrinsicHeight - computeMaxIntrinsicHeight This matches the pattern already used by other methods that call _computeColumnWidths(), such as computeDryLayout (line 1274), performLayout (line 1318), and paint (line 1461). All four methods now return 0.0 for empty tables, which is consistent with the behavior of other dimension methods. Added comprehensive test coverage to verify that empty tables handle intrinsic size queries without crashing.

The check in computeMaxIntrinsicHeight was redundant since the method delegates to getMinIntrinsicHeight(), which eventually calls computeMinIntrinsicHeight() where the same check already exists. This simplifies the code while maintaining the same functionality. The checks in computeMinIntrinsicWidth, computeMaxIntrinsicWidth, and computeMinIntrinsicHeight remain as they either prevent division by zero or serve as performance optimizations for direct computations.

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

Piinks · 2026-01-07T00:22:26Z

Analysis and merge conflicts should be set now.

auto-submit · 2026-01-07T00:59:14Z

autosubmit label was removed for flutter/flutter/178217, because - The status or check suite Linux flutter_plugins has failed. Please fix the issues identified (or deflake) before re-applying this label.

auto-submit · 2026-01-07T02:45:26Z

autosubmit label was removed for flutter/flutter/178217, because - The status or check suite Google testing has failed. Please fix the issues identified (or deflake) before re-applying this label.

Piinks · 2026-01-07T15:05:37Z

Confirmed Google testing failure is unrelated to this change.

…lutter/flutter#178217)

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…lutter/flutter#178217)

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Fix division by zero in RenderTable intrinsic size methods#178217

Fix division by zero in RenderTable intrinsic size methods#178217
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777genius:fix/table-division-by-zero

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