Aliaksandr Kalenik f1253c7139 LibWeb: Fix grid placement when using unresolved named grid lines ...

This patch fixes an issue where grid items using `grid-area: <name>`
with no matching named grid area or lines would be incorrectly placed
at position 0.

According to https://www.w3.org/TR/css-grid-1/#line-placement:
1. When a `<custom-ident>` doesn't match any named line, placement
   should fall back to the first implicit grid line
2. When the same `<custom-ident>` is given for both `grid-*-start` and
   `grid-*-end` (which happens with `grid-area: name`), and both fall
   back to the same implicit line, the resulting span is 1

Previously, the fallback values were hardcoded to 0 and 1, which placed
items in track 0. The fix changes the fallback to use
`m_explicit_line_count` (the first implicit line index) for both start
and end identifiers. When both reference the same line (start == end),
the existing "both positioned" logic now handles this by setting span=1
and adjusting end accordingly.

2026-01-03 16:41:31 +01:00

..

grid-placement-using-named-grid-lines-009.html

LibWeb: Fix grid placement when using unresolved named grid lines

2026-01-03 16:41:31 +01:00