FA-80170 / Typography line breaking / Member archive

Kerning and ligature line measure: kern pair case sensitivity · case 05

Lowercase pairs receive the tighter uppercase kerning value.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input [words, width]. Glyph widths: i,l,j,.,, 4; t,f 6; m 15; w 14; M 16; W 18; other lowercase 10; other uppercase 13; space 5. Within a word, fi/fl/ff form ligatures (11/11/12) with no kerning into or out of them; case-sensitive kern pairs apply between adjacent glyphs; "|" is a non-joiner (invisible, blocks ligatures and kerning). No kerning across spaces. Greedy fill. Return [[text, width]].

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: kern pair case sensitivity	`[["Vat", 26], ["office", 46], ["flow", 35], ["LA", 26], ["staff.", 42], ["AT", 26]]`	`[["Vat", 27], ["office", 46], ["flow", 35], ["LA", 26], ["staff.", 42], ["AT", 26]]`	Failed

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