In quirks mode, the body element expands to fill its parent (the html
element) when height is auto, per the quirks spec section 3.7.
This quirk applies when:
- The document is in quirks mode
- The body element has height: auto
- The body is not absolutely/fixed positioned
- The body is not floated
- The body is not inline-level
The quirks mode percentage height calculation quirk was incorrectly
applied to anonymous boxes (like the internal flex wrapper inside
buttons), causing buttons to collapse to zero height.
Per the quirks spec, the percentage height quirk:
- Only applies to DOM elements, not anonymous boxes
- Does not apply to flex/grid items (they resolve against their
container)
- Does not apply to table-related display types
This patch:
1. Excludes anonymous boxes and flex/grid items from the quirk in
should_treat_height_as_auto()
2. Adds quirks mode percentage height walk-up in
calculate_inner_height() for inline-level boxes
3. Removes the incorrect flex/grid container exclusion from
BlockFormattingContext (the quirk applies to containers, not items)
Add tests to verify:
- Buttons have reasonable height in quirks mode (not collapsed)
- Flex containers with percentage height use quirks walk-up to viewport
- Flex items with percentage height do NOT use quirks walk-up
