Support CSS border-spacing on tables#1321
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The parser only honored the legacy cellspacing attribute; the border-spacing property was ignored from any source, even though default.css declared it, and the writer never emitted cell spacing, so it was lost on every HTML round trip. - Parse border-spacing (one- and two-value forms) from the cascade, with browser precedence: border-collapse:collapse forces zero, CSS beats the cellspacing attribute, falling back to the 0.5pt margin importer default. Margins are now tracked per axis so asymmetric spacing lays out correctly. - Emit border-spacing on the table tag when the cells' margins differ from the default, so cellspacing/border-spacing survives writing. - Remove the dead border-spacing declaration from default.css: with the property now honored, the merged cascade would let it override every cellspacing attribute and the Apple-parity 0.5pt default. Co-Authored-By: Claude Fable 5 <[email protected]>
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Summary
border-spacingwas declared in default.css but never consumed by the table parser — only the legacycellspacingattribute worked — and the HTML writer never emitted cell spacing, so any spacing was silently lost on an HTML → attributed string → HTML round trip (e.g.cellspacing="10"came back as the 1px default).BuilderState+Tables.swift):handleTableStartnow readsborder-spacingfrom the CSS cascade (inline styles and stylesheets), supporting the one-value and two-value (horizontal vertical) forms. Precedence follows browsers:border-collapse: collapseforces zero spacing, CSSborder-spacingbeats thecellspacingattribute, and the 0.5pt-margin importer default applies otherwise. Cell margins are tracked per axis, so asymmetric spacing lays out correctly (layout already reads margins per edge).HTMLWriter.swift): the<table>tag emitsborder-spacing(first cell's margins × 2) whenever it differs from the 1px default, collapsed to one value when both axes match. Collapsed tables skip it.border-spacing: 2pxdeclaration. Now that the property is honored, the merged cascade cannot distinguish UA-origin from author-origin styles, so keeping it would override everycellspacingattribute and change the plain-table default away from the Apple-importer-parity 0.5pt margin pinned byTextBlockAppKitParityTests.Test plan
border-spacing, CSS-over-attribute precedence, and collapse-ignores-spacing.cellspacing="10"is written asborder-spacing:10pxand reparses to 5pt margins;border-spacing: 8px 4pxsurvives asymmetrically; default tables emit noborder-spacing.🤖 Generated with Claude Code