vyaz-monorepo / core/src / FontMetrics

Interface: FontMetrics

Defined in: core/src/types/FontTypes.ts:12

Physical font metrics (in pixels for a given fontSize)

Properties

ascent

ascent: number

Defined in: core/src/types/FontTypes.ts:14

Rise above baseline

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capHeight

capHeight: number

Defined in: core/src/types/FontTypes.ts:18

Cap height

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descent

descent: number

Defined in: core/src/types/FontTypes.ts:16

Descent below baseline (positive number!)

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sourceTable?

optional sourceTable?: "hhea" | "OS/2" | "canvas" | "fallback"

Defined in: core/src/types/FontTypes.ts:28

Which font table was used for ascent/descent: 'hhea' — hhea.ascender/descender (browser mode) 'OS/2' — OS/2.usWinAscent/usWinDescent (Office mode) 'canvas' — canvas.measureText (browser fallback) 'fallback' — empirical formula

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strikeoutThickness?

optional strikeoutThickness?: number

Defined in: core/src/types/FontTypes.ts:72

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strikeoutTop?

optional strikeoutTop?: number

Defined in: core/src/types/FontTypes.ts:71

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typoAscFrac?

optional typoAscFrac?: number

Defined in: core/src/types/FontTypes.ts:34

OS/2.typoAscender / (OS/2.typoAscender − OS/2.typoDescender) — the font's own ascent-side share of its typo em-box. undefined when the font has no OS/2 table (e.g. canvas-fallback metrics).

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underlineThickness?

optional underlineThickness?: number

Defined in: core/src/types/FontTypes.ts:70

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underlineTop?

optional underlineTop?: number

Defined in: core/src/types/FontTypes.ts:69

Font-defined decoration geometry, px, measured from the baseline with y pointing down, each the top edge of the stroke: underline from post.underlinePosition / underlineThickness, strikeout from OS/2.yStrikeoutPosition / yStrikeoutSize (so strikeoutTop is negative). undefined when the table is missing. mode: 'office' draws decorations exactly here (PowerPoint, measured).

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unitsPerEm

unitsPerEm: number

Defined in: core/src/types/FontTypes.ts:20

Original font UPM (for reference)

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useTypoMetrics?

optional useTypoMetrics?: boolean

Defined in: core/src/types/FontTypes.ts:60

OS/2.fsSelection bit 7 — the font's own declaration that line spacing should be driven by its typo metrics rather than win/hhea. undefined when the font has no OS/2 table.

Together with typoAscFrac / winAscFrac, this is how mode: 'office' places the baseline at style.lineHeight === 1 (see OFFICE_BASELINE_RATIO in PositioningEngine.ts): for the common case (useTypoMetrics false/undefined) PowerPoint's baseline sits at winAscFrac of the line box (Roboto 0.7917, Arial 0.8103, Times New Roman 0.8047, Georgia 0.8070, Verdana 0.8272, Courier New 0.7349, Tahoma 0.8289 — each inside the range its PDF baselines allow, 12–144 pt; typoAscFrac is the fallback when win metrics are missing). A font with useTypoMetrics true (found via scripts/office-metrics/gen-font-grid-diagnostic.ts: Unifont is the one oracle font with the bit set) does not fit that formula — only one such font has been measured so far, not enough to derive its own rule, so it falls back to the flat OFFICE_BASELINE_RATIO (still open, see RESULTS.md).

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winAscFrac?

optional winAscFrac?: number

Defined in: core/src/types/FontTypes.ts:40

OS/2.winAscent / (OS/2.winAscent + OS/2.winDescent) — the font's own ascent-side share of its win (legacy Windows/GDI) em-box. undefined when the font has no OS/2 table.