Test interaction between boxes and mixed script.
Test soft breaking on box spacing.
Test line breaking in boxes.
Handle ancestor boxes in rich layout.
Add ancestor boxes to interface.
Implement finding box edges.
Allow extracting ResolvedBox from WithSpan.
Implement set operations on [ResolvedBox].
Allow extracting spacing from ResolvedBox.
Make paragraph direction explicit in tests.
Store direction in ResolvedBox.
Add required textDirection to TextOptions.
Link ResolvedSpan to boxes.
Use ResolvedBox when flattening trees.
Improve code readability with type alias.
Separate WithSpan for sharing with other modules.
Test layout with mixed font sizes.
Deduplicate pagination code.