Fix different column gallery image sizes

[mukeshpanchal27]

Summary

Part of #2449

Follow-up to #2534

Relevant technical choices

How to Test

1. Add a Gallery block.
2. Insert any number of images
3. Set different columns
4. Verify the image sizes.

Use of AI Tools

N/A

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.47%. Comparing base (a7f0b48) to head (6990e4c).

Additional details and impacted files

@@                    Coverage Diff                    @@
##           fix/2449-equal-column    #2543      +/-   ##
=========================================================
+ Coverage                  70.42%   70.47%   +0.05%     
=========================================================
  Files                         91       91              
  Lines                       7865     7879      +14     
=========================================================
+ Hits                        5539     5553      +14     
  Misses                      2326     2326              

Flag	Coverage Δ
multisite	70.47% <100.00%> (+0.05%)	⬆️
single	35.81% <100.00%> (+0.11%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Copilot]

Pull request overview

This PR extends the Auto Sizes (“enhanced responsive images”) logic for core/gallery so sizes can better reflect actual image widths when the gallery has incomplete rows (e.g., different columns vs. image counts), and adds/updates PHPUnit coverage for those scenarios.

Changes:

• Track total gallery images and compute per-image relative width based on whether an image falls in a full vs. incomplete row.
• Add a new data-driven gallery test matrix for varying (image_count, columns) combinations.
• Update gallery test markup generation to emit column-specific gallery classes.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
plugins/auto-sizes/includes/improve-calculate-sizes.php	Adds gallery context and per-image width logic for incomplete rows when calculating container-relative width.
plugins/auto-sizes/tests/test-improve-calculate-sizes.php	Adds expanded gallery test coverage and adjusts gallery markup helper to include columns classes.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: mukeshpanchal27 <mukesh27@git.wordpress.org>
Co-authored-by: westonruter <westonruter@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[westonruter]

Given this Gallery:

I see successfully that the first two images have sizes="(max-width: 322px) 100vw, 322px" and the last has sizes="(max-width: 645px) 100vw, 645px".

[westonruter]

Probably should get this merged into the other branch since this is a critical change which probably belongs in that initial PR.