Enhanced Responsive Images: Account for Gallery and grid layouts in sizes calculation

[meravi]

Summary

Addresses #2449

Updates Enhanced Responsive Images so Gallery blocks and grid-style Group layouts propagate equal-width container constraints to child images for more accurate sizes attributes.

Technical Notes

• added layout column-count/context propagation for Gallery and grid-style Group layouts
• reused the existing container-relative sizing calculation for direct child image-like blocks
• added PHPUnit coverage for Gallery and Group grid layouts
• updated the Gallery test helper to serialize empty attributes like core block markup

Props: ravikhadka

[github-actions]

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Co-authored-by: meravi <ravikhadka@git.wordpress.org>
Co-authored-by: westonruter <westonruter@git.wordpress.org>

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[codecov]

Codecov Report

❌ Patch coverage is 96.96970% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 69.44%. Comparing base (518db24) to head (d9353eb).
⚠️ Report is 2 commits behind head on trunk.

Files with missing lines	Patch %	Lines
...ns/auto-sizes/includes/improve-calculate-sizes.php	96.96%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk    #2453      +/-   ##
==========================================
+ Coverage   69.33%   69.44%   +0.10%     
==========================================
  Files          90       90              
  Lines        7749     7779      +30     
==========================================
+ Hits         5373     5402      +29     
- Misses       2376     2377       +1     

Flag	Coverage Δ
multisite	69.44% <96.96%> (+0.10%)	⬆️
single	35.96% <96.96%> (+0.23%)	⬆️

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[westonruter]

Just a couple quick drive-by suggestions. I haven't reviewed this otherwise, and I'm not really very familiar with how it works.

[westonruter]

Suggested change

	$column_count = isset( $parent_block->context['column_count'] ) ? (int) $parent_block->context['column_count'] : 0;
	$column_count = (int) ( $parent_block->context['column_count'] ?? 0 );

[westonruter]

Suggested change

	$column_count = isset( $block['attrs']['layout']['columnCount'] ) ? (int) $block['attrs']['layout']['columnCount'] : 0;
	$column_count = (int) ( $block['attrs']['layout']['columnCount'] ?? 0 );

[westonruter]

Suggested change

	$column_count = isset( $block['attrs']['columns'] ) ? (int) $block['attrs']['columns'] : 0;
	$column_count = (int) ( $block['attrs']['columns'] ?? 0 );