API reference

Every public class, method, and event in @codexo/exojs. Generated from source.

classGlyphMetrics

@codexo/exojs / rendering / stable

The LOGICAL typographic metrics of one font variant - advances and kerning, in logical pixels, at the logical font size. This is the half of a glyph that layout consumes, and it is deliberately kept out of GlyphAtlas: an atlas is a RASTER resource whose identity includes a pixel density, while an advance is a property of the typeface and the font size alone. Splitting them is what makes the two invariants of HiDPI text hold by construction rather than by luck: - the same string lays out identically at every `pixelRatio`, because the numbers layout reads never went near a raster grid; - Text.measure answers without rasterizing anything, so a measurement cannot allocate an atlas, cannot claim atlas space, and cannot depend on which Application happens to exist. One instance per `family` x `fontStyle` x `fontVariant` x `fontWeight`, shared by every atlas of that variant regardless of mode, SDF radius or pixel ratio - see GlyphAtlasPool.getMetrics. Satisfies GlyphProvider so it can drive a measurement-only layout pass. The GlyphInfo it hands out carries a real `advance` and zero geometry: there is no tile, no page and no UV rectangle behind it, and a caller that needs those wants an atlas instead.

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methods

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Import

import { GlyphMetrics } from '@codexo/exojs'

The LOGICAL typographic metrics of one font variant - advances and kerning, in logical pixels, at the logical font size.

This is the half of a glyph that layout consumes, and it is deliberately kept out of GlyphAtlas: an atlas is a RASTER resource whose identity includes a pixel density, while an advance is a property of the typeface and the font size alone. Splitting them is what makes the two invariants of HiDPI text hold by construction rather than by luck:

- the same string lays out identically at every `pixelRatio`, because the numbers layout reads never went near a raster grid; - Text.measure answers without rasterizing anything, so a measurement cannot allocate an atlas, cannot claim atlas space, and cannot depend on which Application happens to exist.

One instance per `family` x `fontStyle` x `fontVariant` x `fontWeight`, shared by every atlas of that variant regardless of mode, SDF radius or pixel ratio - see GlyphAtlasPool.getMetrics.

Satisfies GlyphProvider so it can drive a measurement-only layout pass. The GlyphInfo it hands out carries a real `advance` and zero geometry: there is no tile, no page and no UV rectangle behind it, and a caller that needs those wants an atlas instead.

Constructors1

new(font: FontVariantKeyEverything that decides which glyphs a text run is drawn from. Named rather than positional because the four values are all strings and three of them default t…): GlyphMetrics

Methods6

advance(char: string, fontSize: number): number

Horizontal advance of char at fontSize logical pixels.

clear(): void

Drop every cached measurement. Called when the variant's FontFace finishes loading: everything measured before that point came from the fallback face and is wrong.

cssFont(size: number): string

The CSS font shorthand for this variant at size logical pixels.

getFontMetrics(fontSize: number): TextFontMetricsVertical font metrics in logical pixels at one font size, as a glyph source reports them. Everything is measured from the line's own baseline: `ascent` is how…

Vertical metrics of this variant at fontSize. The ascent and descent come from the font's own bounding box where the platform reports one, so every string of the variant shares one baseline; the x-height is measured from a lowercase letter's ink, which is the only way to get it from Canvas 2D at all. Where a measurement is missing the value degrades to a fraction of the font size.

getGlyph(char: string, fontSize: number): GlyphInfoCached glyph data stored in an atlas page after rasterization.

Return metrics for the given character at the given font size.

getKerning(prev: string, next: string, fontSize: number): number

Return the kerning adjustment (in pixels) between two adjacent characters. Positive values add space; negative values pull glyphs together. Optional - callers treat a missing method as zero kerning.

Source

src/rendering/text/GlyphMetrics.ts