FA-80739 / Bidirectional text layout / Member archive

Direction-relative alignment: start alignment mapping · case 04

Start-aligned RTL paragraphs are left aligned.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input [line width, content width, align, rtl]. justify (last line) behaves as start. start = left for LTR, right for RTL; end is the opposite. Overflowing centered content aligns to start. center offset is floor(slack/2) for LTR and ceil(slack/2) for RTL. Return the x offset of the content.

Why this case matters

Mixed right-to-left and left-to-right text must resolve levels and visual order exactly, or words, numbers and carets land in the wrong place.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: start alignment mapping	`0`	`6`	Failed

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