Add CSS Grid parsing (track lists, placement, areas, subgrid, shorthands)#223
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jhaygood86 wants to merge 7 commits into
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Add CSS Grid parsing (track lists, placement, areas, subgrid, shorthands)#223jhaygood86 wants to merge 7 commits into
jhaygood86 wants to merge 7 commits into
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…o-*) Introduce the shared GridTrackListGrammar parsing a full <track-list>: lengths, percentages, fr, auto, min-content/max-content, minmax(), fit-content(), repeat(N, ...) expanded inline, and repeat(auto-fill|auto-fit, ...) recorded as a layout-time section. The grammar emits GridTemplate / GridTrackSize model types. Add the grid-template-columns / grid-template-rows / grid-auto-columns / grid-auto-rows / grid-auto-flow longhands. Each is validated by the grammar (grid-auto-flow as [row|column] || dense) and preserves the authored text as a TokenValue, mirroring the aspect-ratio converter.
Introduce the shared GridLineGrammar for a single <grid-line> (auto | <integer> | span <integer>) and the placement longhands grid-column-start/end and grid-row-start/end. Add the grid-column / grid-row / grid-area shorthands via a shared GridPlacementShorthand that splits on '/', validates each component with the grammar, preserves each component's internal whitespace, and applies the CSS Grid 8.3.1 omitted-value copy rule. The result distributes to the longhands through a MappedShorthandValue.
Add the justify-items / justify-self longhands and the place-items / place-content / place-self shorthands, reusing the existing align-items / align-content / align-self / justify-content value grammars. The place-* shorthands use a periodic <align> <justify>? converter so a single value applies to both axes.
Add the shared GridTemplateAreasGrammar, which parses the quoted-string rows into a rectangular GridAreas grid (equal columns per row, each named area a single filled rectangle; '.' runs are empty cells), plus the grid-template-areas property and its text-preserving converter. Also accept SquareBracketOpen/Close tokens in ValueBuilder so a grid line-names group [name ...] survives strict value parsing, mirroring the existing unicode-range Range-token handling. This is a prerequisite for named grid lines.
Extend GridLineGrammar to accept a bare <custom-ident> named line and the <custom-ident> <integer> Nth-line form (guarding against auto/span/none and the CSS-wide keywords). Extend GridTrackListGrammar to collect [name] groups in the top-level track list into GridTemplate.LineNames (name -> sorted 1-based line numbers); names inside repeat() are rejected. The bare custom-ident now drives the grid-column/row/area omitted-value copy rule.
Extend GridTrackListGrammar to accept subgrid [ <line-name-list> ]? on grid-template-columns/rows (CSS Grid Level 2 9): the axis adopts the parent grid's tracks, carrying no track sizes, with an optional run of [name] line-name groups recorded per line. A track size after subgrid, subgrid not first, repeat() of line names, or an unclosed bracket are all rejected. This is the parser subset only; the typed-cascade CssProperty<T> plumbing from the source commit is intentionally not ported.
Implement the grid-template (CSS Grid 7.4) and grid (7.8) shorthands as a CSS-OM shorthand-to-longhand expansion. A shared GridTemplateShorthand helper splits the value on the top-level '/', runs the areas-form row scanner (feeding strings to GridTemplateAreasGrammar and synthesizing the grid-template-rows track list), and validates each slice via the existing grid grammars; TryParseAutoFlowSide handles the [auto-flow && dense?] <track-size>* forms. Two thin converters emit a MappedShorthandValue over the covered longhands, resetting omitted longhands to their initial value. Register both via a new AddLogicalShorthand so they parse/expand but are excluded from serialization reconstruction (GetShorthands), so ToCss never re-collapses the longhands into a mega-shorthand.
jhaygood86
marked this pull request as ready for review
July 24, 2026 20:39
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Summary
Adds CSS Grid parsing to ExCSS (CSS Grid Layout Level 1 / Level 2): value grammars, properties, converters, and serialization.
Delivered as 7 ordered commits:
GridTrackListGrammar(lengths,%,fr,auto,min-content/max-content,minmax(),fit-content(),repeat()incl.auto-fill/auto-fit);grid-template-columns/-rows,grid-auto-columns/-rows/grid-auto-flow.GridLineGrammar(auto|<integer>|span n| named);grid-column/-row-start/-endlonghands + thegrid-column/grid-row/grid-areashorthands (with the §8.3.1 omitted-value copy rule).justify-items/justify-self+place-items/place-content/place-self(reusing the existingalign-*/justify-contentconverters).grid-template-areas—GridTemplateAreasGrammar(validates rectangular named areas). Also makesValueBuilderaccept[/]tokens in a value (prerequisite for named lines; mirrors the existing unicode-range Range-token handling).[name]groups in track lists +<custom-ident>/Nth named-line placement.subgrid— accepted in the track-list grammar (subgrid [ <line-name-list> ]?).grid/grid-templatemega-shorthands — viaGridTemplateShorthand; excluded from serialization reconstruction soToCss()never re-collapses the longhands.Design
Every grid value-converter validates via the grammar and preserves the authored text (mirroring the existing
AspectRatioValueConverter). The grammar model types (GridTemplate,GridLine,GridAreas) back the grammars and tests.Portability
Builds clean across all 8 target frameworks (0 errors/warnings). C# stays within LangVersion 9.
Tests
GridTrackListGrammarTests,GridLineGrammarTests,GridTemplateAreasGrammarTests,GridTemplateShorthandTests, plus per-feature property round-trip tests — 174 new cases. Full suite green at 1690 passing, no regressions.