FA-79980 / Typography line breaking / Member archive

Widow and orphan page breaking: widow threshold · case 05

Carry-overs one line short of the widow minimum are left in place.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input [paragraph line counts, page height, min orphan lines, min widow lines]. Lines flow onto pages. When a paragraph must break on a page that already holds lines, at least min widow lines must carry to the next page (move lines forward) and, if the paragraph starts on this page, at least min orphan lines must stay (else move it all). A paragraph that exactly fits stays. Constraints are waived on an empty page. Return lines per page.

Why this case matters

Line breaking decides where paragraphs wrap on screen and in print; a wrong decision point shifts every following line.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: widow threshold	`[4, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4]`	`[4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4]`	Failed

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