fix(text): render variable font styles at their named instances (#773)

* fix(text): render variable font styles at their named instances

Installed variable fonts such as SF Pro list every named instance, but
font-kit loads each one at the default weight, so the desktop loader
rejected Medium and Bold and the canvas fell back to a substitute. Even
when a variable face was loaded, CanvasKit drew it at its default axes:
Medium rendered as Regular and Bold as a synthetic bold.

The desktop loader now falls back to a variable face whose wght axis
covers the requested weight. The renderer applies the coordinates of the
named instance matching the style, or the clamped weight when none
matches, beneath any explicit font variations on the text.

* fix(text): validate variable font tables and leave loading to the host

Check name-table records and string ranges, the fvar header size, and
axis and instance record sizes, so a malformed font falls back to the
style weight instead of throwing while text is shaped.

Drop the desktop loader's variable-face fallback; system font discovery
moves to fontique, which lists variable faces with their weight axes.

CHANGELOG.md

@@ -24,6 +24,7 @@
 - Evaluate the `**` operator in the AI and MCP `calc` tool, which its own description advertised but which the tool rejected. `calc` now accepts exactly the arithmetic it documents — `+ - * / % **`, parentheses and `min max floor ceil round abs sqrt pow` — and no longer evaluates undocumented expressions such as `random()`, factorials, trigonometry, strings, arrays, or property access.
 - Show Chinese, Japanese, Korean, and Arabic characters in a fallback font when the text's own font is unavailable and another font substitutes for it, instead of drawing missing-glyph boxes (#746).
 - Explain in the font issues banner when an installed font, such as PingFang on macOS 15 and later, stores outlines in a format OpenPencil cannot draw yet, instead of spending over a second trying to load each of its styles (#746).
+- Render the Medium, Semibold, Bold, and other styles of variable fonts at their named weights instead of drawing Regular or a synthetic bold.
 
 ### Security
 

packages/core/src/canvas/text/index.ts

@@ -293,11 +293,18 @@ function getParagraphTextAlign(
   }
 }
 
+/** Explicit axes win over the named-instance axes of a variable face (`implicit`). */
 export function textFontVariations(
-  variations: SceneNode['fontVariations'] | undefined
+  variations: SceneNode['fontVariations'] | undefined,
+  implicit: SceneNode['fontVariations'] | null = null
 ): TextFontVariations[] | undefined {
-  if (!variations || variations.length === 0) return undefined
-  return variations.map((variation) => ({ axis: variation.axis, value: variation.value }))
+  const explicitAxes = new Set(variations?.map((variation) => variation.axis))
+  const merged = [
+    ...(implicit ?? []).filter((variation) => !explicitAxes.has(variation.axis)),
+    ...(variations ?? [])
+  ]
+  if (merged.length === 0) return undefined
+  return merged.map((variation) => ({ axis: variation.axis, value: variation.value }))
 }
 
 export function textFontFeatures(
@@ -386,21 +393,23 @@ function pushStyleRun(
   const style = run.style
   const runLineHeight = style.lineHeight !== undefined ? style.lineHeight : node.lineHeight
   const runFontSize = style.fontSize ?? baseFontSize
+  const runFamily = style.fontFamily ?? (node.fontFamily || DEFAULT_FONT_FAMILY)
+  const runWeight = style.fontWeight ?? node.fontWeight
+  const runItalic = style.italic ?? node.italic
 
   const textStyle = new ck.TextStyle({
     color: styleRunColor(ck, style, baseColor),
-    fontFamilies: fontFamilies(
-      style.fontFamily ?? (node.fontFamily || DEFAULT_FONT_FAMILY),
-      style.fontWeight ?? node.fontWeight,
-      style.italic ?? node.italic
-    ),
+    fontFamilies: fontFamilies(runFamily, runWeight, runItalic),
     fontSize: runFontSize,
     locale: styleRunLanguage(style, node),
     fontStyle: {
-      weight: { value: style.fontWeight ?? node.fontWeight } as FontWeight,
-      slant: (style.italic ?? node.italic) ? ck.FontSlant.Italic : ck.FontSlant.Upright
+      weight: { value: runWeight } as FontWeight,
+      slant: runItalic ? ck.FontSlant.Italic : ck.FontSlant.Upright
     },
-    fontVariations: textFontVariations(style.fontVariations ?? node.fontVariations),
+    fontVariations: textFontVariations(
+      style.fontVariations ?? node.fontVariations,
+      fontManager.namedInstanceVariations(runFamily, weightToStyle(runWeight, runItalic))
+    ),
     fontFeatures: textFontFeatures(style.fontFeatures ?? node.fontFeatures),
     letterSpacing: style.letterSpacing ?? (node.letterSpacing || 0),
     decoration: textDecorationValue(ck, style.textDecoration ?? node.textDecoration),
@@ -498,7 +507,13 @@ export function buildParagraph(
       weight: { value: node.fontWeight } as FontWeight,
       slant: node.italic ? ck.FontSlant.Italic : ck.FontSlant.Upright
     },
-    fontVariations: textFontVariations(node.fontVariations),
+    fontVariations: textFontVariations(
+      node.fontVariations,
+      fontManager.namedInstanceVariations(
+        node.fontFamily || DEFAULT_FONT_FAMILY,
+        weightToStyle(node.fontWeight, node.italic)
+      )
+    ),
     fontFeatures: textFontFeatures(node.fontFeatures),
     letterSpacing: node.letterSpacing || 0,
     decoration: textDecorationValue(ck, node.textDecoration),

packages/core/src/text/font/style.ts

@@ -45,20 +45,4 @@ export function chooseLocalFontMatch<T extends FontFamilyStyle>(
   return undefined
 }
 
-export function isVariableFont(data: ArrayBuffer): boolean {
-  if (data.byteLength < 12) return false
-  const view = new DataView(data)
-  const numTables = view.getUint16(4)
-  for (let i = 0; i < numTables && 12 + i * 16 + 4 <= data.byteLength; i++) {
-    const tag = String.fromCharCode(
-      view.getUint8(12 + i * 16),
-      view.getUint8(12 + i * 16 + 1),
-      view.getUint8(12 + i * 16 + 2),
-      view.getUint8(12 + i * 16 + 3)
-    )
-    if (tag === 'fvar') return true
-  }
-  return false
-}
-
 export { weightToFigmaStyle } from '@open-pencil/fig/node-change'

packages/core/src/text/font/variation.ts

@@ -0,0 +1,126 @@
+import { styleToWeight } from '@open-pencil/scene-graph'
+import type { FontVariation } from '@open-pencil/scene-graph'
+
+interface TableRange {
+  offset: number
+  length: number
+}
+
+const WINDOWS_PLATFORM = 3
+const MAC_PLATFORM = 1
+const ENGLISH_US = 0x409
+const NAME_HEADER_SIZE = 6
+const NAME_RECORD_SIZE = 12
+const FVAR_HEADER_SIZE = 16
+const AXIS_RECORD_SIZE = 20
+
+function sfntTable(view: DataView, tag: string): TableRange | null {
+  if (view.byteLength < 12) return null
+  const numTables = view.getUint16(4)
+  for (let i = 0; i < numTables; i++) {
+    const record = 12 + i * 16
+    if (record + 16 > view.byteLength) return null
+    let recordTag = ''
+    for (let c = 0; c < 4; c++) recordTag += String.fromCharCode(view.getUint8(record + c))
+    if (recordTag !== tag) continue
+    const offset = view.getUint32(record + 8)
+    const length = view.getUint32(record + 12)
+    return offset + length <= view.byteLength ? { offset, length } : null
+  }
+  return null
+}
+
+export function isVariableFont(data: ArrayBuffer): boolean {
+  return sfntTable(new DataView(data), 'fvar') !== null
+}
+
+function fixed(view: DataView, offset: number): number {
+  return view.getInt32(offset) / 65536
+}
+
+function normalizeStyleName(style: string): string {
+  return style.toLowerCase().replace(/\s+/g, '')
+}
+
+function fontName(view: DataView, name: TableRange, nameId: number): string | null {
+  const end = name.offset + name.length
+  if (name.length < NAME_HEADER_SIZE) return null
+  const count = view.getUint16(name.offset + 2)
+  const strings = name.offset + view.getUint16(name.offset + 4)
+  if (name.offset + NAME_HEADER_SIZE + count * NAME_RECORD_SIZE > end) return null
+  let fallback: string | null = null
+  for (let i = 0; i < count; i++) {
+    const record = name.offset + NAME_HEADER_SIZE + i * NAME_RECORD_SIZE
+    if (view.getUint16(record + 6) !== nameId) continue
+    const platform = view.getUint16(record)
+    const language = view.getUint16(record + 4)
+    const length = view.getUint16(record + 8)
+    const start = strings + view.getUint16(record + 10)
+    if (start + length > end) continue
+    const bytes = new Uint8Array(view.buffer, view.byteOffset + start, length)
+    if (platform === WINDOWS_PLATFORM) {
+      let value = ''
+      for (let c = 0; c + 1 < length; c += 2)
+        value += String.fromCharCode((bytes[c] << 8) | bytes[c + 1])
+      if (language === ENGLISH_US) return value
+      fallback ??= value
+    } else if (platform === MAC_PLATFORM) {
+      fallback ??= String.fromCharCode(...bytes)
+    }
+  }
+  return fallback
+}
+
+/**
+ * Returns the axis coordinates a variable font needs to render `style`, preferring the named
+ * instance with that name (for example SF Pro `Medium` is `wght` 510) and otherwise clamping the
+ * style's weight to the `wght` axis. Returns `null` for static fonts.
+ */
+export function namedInstanceVariations(data: ArrayBuffer, style: string): FontVariation[] | null {
+  const view = new DataView(data)
+  const fvar = sfntTable(view, 'fvar')
+  if (!fvar || fvar.length < FVAR_HEADER_SIZE) return null
+
+  const axesOffset = fvar.offset + view.getUint16(fvar.offset + 4)
+  const axisCount = view.getUint16(fvar.offset + 8)
+  const axisSize = view.getUint16(fvar.offset + 10)
+  const instanceCount = view.getUint16(fvar.offset + 12)
+  const instanceSize = view.getUint16(fvar.offset + 14)
+  if (axisSize < AXIS_RECORD_SIZE || instanceSize < 4 + axisCount * 4) return null
+  if (
+    axesOffset + axisCount * axisSize + instanceCount * instanceSize >
+    fvar.offset + fvar.length
+  ) {
+    return null
+  }
+
+  const axes = Array.from({ length: axisCount }, (_, index) => {
+    const axis = axesOffset + index * axisSize
+    let tag = ''
+    for (let c = 0; c < 4; c++) tag += String.fromCharCode(view.getUint8(axis + c))
+    return { tag, min: fixed(view, axis + 4), max: fixed(view, axis + 12) }
+  })
+
+  const name = sfntTable(view, 'name')
+  const requested = normalizeStyleName(style)
+  const instancesOffset = axesOffset + axisCount * axisSize
+  const instance = name
+    ? Array.from(
+        { length: instanceCount },
+        (_, index) => instancesOffset + index * instanceSize
+      ).find((offset) => {
+        const instanceName = fontName(view, name, view.getUint16(offset))
+        return instanceName !== null && normalizeStyleName(instanceName) === requested
+      })
+    : undefined
+  if (instance !== undefined) {
+    return axes.map((axis, axisIndex) => ({
+      axis: axis.tag,
+      value: fixed(view, instance + 4 + axisIndex * 4)
+    }))
+  }
+
+  const weight = axes.find((axis) => axis.tag === 'wght')
+  if (!weight) return []
+  return [{ axis: 'wght', value: Math.min(weight.max, Math.max(weight.min, styleToWeight(style))) }]
+}

packages/core/src/text/fonts.ts

@@ -2,19 +2,20 @@
 
 import type { CanvasKit, TypefaceFontProvider } from 'canvaskit-wasm'
 
-import type { SceneGraph } from '@open-pencil/scene-graph'
+import type { FontVariation, SceneGraph } from '@open-pencil/scene-graph'
 
 import { DEFAULT_FONT_FAMILY, IS_BROWSER } from '#core/constants'
 import {
   chooseLocalFontMatch,
-  isVariableFont,
   normalizeFontFamily,
   styleToWeight,
   weightToStyle
 } from '#core/text/font/style'
+import { isVariableFont, namedInstanceVariations } from '#core/text/font/variation'
 
 export * from '#core/text/font/sources'
 export * from '#core/text/font/style'
+export * from '#core/text/font/variation'
 import { fontFallbackEntry } from '#core/text/fallbacks'
 import type { FontFallbackScript } from '#core/text/fallbacks'
 import { UnsupportedFontFormatError } from '#core/text/font/sources'
@@ -48,6 +49,7 @@ export class FontManager {
   private unavailableFaces = new Map<string, FontUnavailableReason>()
   private supplementalFamilyData = new Map<string, ArrayBuffer[]>()
   private remoteCoverage = new Map<string, Set<string>>()
+  private instanceVariations = new WeakMap<ArrayBuffer, Map<string, FontVariation[] | null>>()
   private blockedNodeIds = new Set<string>()
   private fontProvider: TypefaceFontProvider | null = null
   private fontProviders = new Set<TypefaceFontProvider>()
@@ -367,6 +369,19 @@ export class FontManager {
     return this.loadedFamilies.get(`${family}|${style}`) ?? null
   }
 
+  /** Axis coordinates for `style` when the loaded face is a variable font, otherwise `null`. */
+  namedInstanceVariations(family: string, style: string): FontVariation[] | null {
+    const data = this.loadedData(family, style)
+    if (!data) return null
+    let byStyle = this.instanceVariations.get(data)
+    if (!byStyle) {
+      byStyle = new Map()
+      this.instanceVariations.set(data, byStyle)
+    }
+    if (!byStyle.has(style)) byStyle.set(style, namedInstanceVariations(data, style))
+    return byStyle.get(style) ?? null
+  }
+
   renderFamily(family: string, _style: string): string {
     // CanvasKit can shape metrics but paint no glyphs for some CJK/Arabic faces registered under a
     // synthetic alias. Keep every shard under the font's source family; character-aware remote

tests/e2e/fonts/variable-weights-visual.spec.ts

@@ -0,0 +1,94 @@
+import { Buffer } from 'node:buffer'
+
+import type { Page } from '@playwright/test'
+
+import type { FontManager } from '#core/text/fonts'
+
+import { expect, test } from '#tests/e2e/fixtures'
+import { CanvasHelper } from '#tests/helpers/canvas'
+import { mockFontsource } from '#tests/helpers/fonts/fontsource'
+import { trackFontModuleResources } from '#tests/helpers/fonts/runtime'
+
+async function openEditor(page: Page): Promise<void> {
+  await trackFontModuleResources(page)
+  // The variable fixture is installed explicitly; remote arrivals must not race it.
+  await mockFontsource(page, [])
+  await page.goto('/?test&no-chrome&no-rulers')
+  await new CanvasHelper(page).waitForInit()
+}
+
+test('variable fonts render each style at its named instance', async ({ page }) => {
+  await openEditor(page)
+
+  const result = await page.evaluate(async () => {
+    const store = window.openPencil?.getStore?.()
+    if (!store?.renderer) throw new Error('OpenPencil renderer not initialized')
+    const fontModuleURL = performance
+      .getEntriesByType('resource')
+      .map((entry) => entry.name)
+      .find((url) => url.includes('/packages/core/src/text/fonts.ts'))
+    if (!fontModuleURL) throw new Error('Active font manager module not found')
+    const { fontManager } = (await import(/* @vite-ignore */ fontModuleURL)) as {
+      fontManager: FontManager
+    }
+    const pageId = store.state.currentPageId
+    for (const id of store.graph.getNode(pageId)?.childIds.slice() ?? []) {
+      store.graph.deleteNode(id)
+    }
+
+    // One variable file serves every style, as installed variable fonts such as SF Pro do.
+    const data = await fetch('/tests/fixtures/fonts/InterVariable-Latin.ttf').then((response) =>
+      response.arrayBuffer()
+    )
+    for (const style of ['Regular', 'Medium', 'SemiBold', 'Bold']) {
+      fontManager.markLoaded('Inter Variable', style, data)
+    }
+
+    const samples = [
+      { label: 'Regular 400', fontWeight: 400 },
+      { label: 'Medium 500', fontWeight: 500 },
+      { label: 'SemiBold 600', fontWeight: 600 },
+      { label: 'Bold 700', fontWeight: 700 },
+      {
+        label: 'Bold, explicit wght 300',
+        fontWeight: 700,
+        fontVariations: [{ axis: 'wght', value: 300 }]
+      }
+    ]
+    const ids = samples.map(
+      (sample, index) =>
+        store.graph.createNode('TEXT', pageId, {
+          name: sample.label,
+          x: 40,
+          y: 40 + index * 56,
+          width: 520,
+          height: 44,
+          text: `${sample.label} — Buttons`,
+          fontFamily: 'Inter Variable',
+          fontSize: 32,
+          fontWeight: sample.fontWeight,
+          fontVariations: sample.fontVariations ?? [],
+          textAutoResize: 'NONE',
+          fills: [
+            { type: 'SOLID', color: { r: 0.04, g: 0.06, b: 0.12, a: 1 }, visible: true, opacity: 1 }
+          ]
+        }).id
+    )
+
+    await store.loadFontsForNodes(ids)
+    store.renderer.invalidateAllPictures()
+    store.requestRender()
+    const image = await store.renderExportImage(ids, 2, 'PNG')
+    if (!image) throw new Error('Export failed')
+    return {
+      image: Array.from(image),
+      readiness: ids.map((id) => {
+        const node = store.graph.getNode(id)
+        return node ? store.renderer?.nodeFontReadiness(node) : 'missing'
+      })
+    }
+  })
+
+  expect(result.readiness).toEqual(['ready', 'ready', 'ready', 'ready', 'ready'])
+  expect(Buffer.from(result.image)).toMatchSnapshot('variable-font-weights.png')
+})

tests/engine/render/canvas/text-font-variations.test.ts

@@ -49,6 +49,19 @@ describe('canvas text font variations', () => {
   test('omits font variations when no axes are set', () => {
     expect(textFontVariations([])).toBeUndefined()
     expect(textFontVariations(undefined)).toBeUndefined()
+    expect(textFontVariations(undefined, [])).toBeUndefined()
+  })
+
+  test('applies named-instance axes of a variable face under explicit axes', () => {
+    const medium = [
+      { axis: 'wdth', value: 100 },
+      { axis: 'wght', value: 510 }
+    ]
+    expect(textFontVariations(undefined, medium)).toEqual(medium)
+    expect(textFontVariations([{ axis: 'wght', value: 650 }], medium)).toEqual([
+      { axis: 'wdth', value: 100 },
+      { axis: 'wght', value: 650 }
+    ])
   })
 
   test('passes imported OpenType feature toggles to CanvasKit text styles', () => {

tests/engine/text/fonts/variations.test.ts

@@ -0,0 +1,198 @@
+import { describe, expect, test } from 'bun:test'
+
+import { FontManager } from '@open-pencil/core'
+
+import { isVariableFont, namedInstanceVariations } from '#core/text/font/variation'
+
+interface Axis {
+  tag: string
+  min: number
+  max: number
+}
+
+interface Instance {
+  name: string
+  coordinates: number[]
+}
+
+function concat(parts: Uint8Array[]): Uint8Array {
+  const out = new Uint8Array(parts.reduce((size, part) => size + part.length, 0))
+  let offset = 0
+  for (const part of parts) {
+    out.set(part, offset)
+    offset += part.length
+  }
+  return out
+}
+
+function words(values: number[], bytes: 2 | 4): Uint8Array {
+  const view = new DataView(new ArrayBuffer(values.length * bytes))
+  values.forEach((value, index) =>
+    bytes === 2 ? view.setUint16(index * 2, value) : view.setInt32(index * 4, value)
+  )
+  return new Uint8Array(view.buffer)
+}
+
+function ascii(tag: string): Uint8Array {
+  return new TextEncoder().encode(tag)
+}
+
+function nameTable(names: string[]): Uint8Array {
+  const strings = names.map((name) =>
+    words(
+      Array.from(name, (character) => character.charCodeAt(0)),
+      2
+    )
+  )
+  const header = words([0, names.length, 6 + names.length * 12], 2)
+  let offset = 0
+  const records = names.map((name, index) => {
+    const record = words([3, 1, 0x409, 256 + index, strings[index].length, offset], 2)
+    offset += strings[index].length
+    return record
+  })
+  return concat([header, ...records, ...strings])
+}
+
+function fvarTable(axes: Axis[], instances: Instance[]): Uint8Array {
+  const header = words([1, 0, 16, 2, axes.length, 20, instances.length, 4 + axes.length * 4], 2)
+  const axisRecords = axes.map((axis) =>
+    concat([
+      ascii(axis.tag),
+      words(
+        [axis.min, axis.min, axis.max].map((value) => value * 65536),
+        4
+      ),
+      words([0, 0], 2)
+    ])
+  )
+  const instanceRecords = instances.map((instance, index) =>
+    concat([
+      words([256 + index, 0], 2),
+      words(
+        instance.coordinates.map((value) => value * 65536),
+        4
+      )
+    ])
+  )
+  return concat([header, ...axisRecords, ...instanceRecords])
+}
+
+function variableFont(axes: Axis[], instances: Instance[]): ArrayBuffer {
+  const tables: Array<[string, Uint8Array]> = [
+    ['fvar', fvarTable(axes, instances)],
+    ['name', nameTable(instances.map((instance) => instance.name))]
+  ]
+  const directory = concat([
+    words([0x0001, 0x0000, tables.length, 0, 0, 0], 2),
+    ...tables.map(([tag, data], index) => {
+      const offset =
+        12 + tables.length * 16 + tables.slice(0, index).reduce((size, [, t]) => size + t.length, 0)
+      return concat([ascii(tag), words([0, offset, data.length], 4)])
+    })
+  ])
+  return concat([directory, ...tables.map(([, data]) => data)]).buffer as ArrayBuffer
+}
+
+const SF_PRO_LIKE = variableFont(
+  [
+    { tag: 'wdth', min: 30, max: 150 },
+    { tag: 'wght', min: 1, max: 1000 }
+  ],
+  [
+    { name: 'Condensed Medium', coordinates: [60, 540] },
+    { name: 'Regular', coordinates: [100, 400] },
+    { name: 'Medium', coordinates: [100, 510] },
+    { name: 'Semibold', coordinates: [100, 590] },
+    { name: 'Bold Italic', coordinates: [100, 700] }
+  ]
+)
+
+describe('namedInstanceVariations', () => {
+  test('uses the coordinates of the named instance matching the style', () => {
+    expect(namedInstanceVariations(SF_PRO_LIKE, 'Medium')).toEqual([
+      { axis: 'wdth', value: 100 },
+      { axis: 'wght', value: 510 }
+    ])
+    expect(namedInstanceVariations(SF_PRO_LIKE, 'Bold Italic')).toEqual([
+      { axis: 'wdth', value: 100 },
+      { axis: 'wght', value: 700 }
+    ])
+  })
+
+  test('matches instance names regardless of case and spacing', () => {
+    expect(namedInstanceVariations(SF_PRO_LIKE, 'SemiBold')).toEqual([
+      { axis: 'wdth', value: 100 },
+      { axis: 'wght', value: 590 }
+    ])
+  })
+
+  test('clamps the style weight to the wght axis without a matching instance', () => {
+    expect(namedInstanceVariations(SF_PRO_LIKE, 'Black')).toEqual([{ axis: 'wght', value: 900 }])
+    const narrow = variableFont([{ tag: 'wght', min: 300, max: 600 }], [])
+    expect(namedInstanceVariations(narrow, 'Bold')).toEqual([{ axis: 'wght', value: 600 }])
+  })
+
+  test('returns null for static fonts', () => {
+    const header = words([0x0001, 0x0000, 0, 0, 0, 0], 2)
+    expect(namedInstanceVariations(header.buffer as ArrayBuffer, 'Medium')).toBeNull()
+    expect(isVariableFont(header.buffer as ArrayBuffer)).toBe(false)
+    expect(isVariableFont(SF_PRO_LIKE)).toBe(true)
+  })
+})
+
+describe('namedInstanceVariations with malformed fonts', () => {
+  function patched(patch: (view: DataView, tableOffset: (tag: string) => number) => void) {
+    const data = SF_PRO_LIKE.slice(0)
+    const view = new DataView(data)
+    const tableRecord = (tag: string) => {
+      for (let i = 0; i < view.getUint16(4); i++) {
+        const record = 12 + i * 16
+        const recordTag = String.fromCharCode(...new Uint8Array(data, record, 4))
+        if (recordTag === tag) return record
+      }
+      throw new Error(`Missing ${tag}`)
+    }
+    patch(view, tableRecord)
+    return data
+  }
+
+  test('skips name records that point outside the font', () => {
+    const data = patched((view, tableRecord) => {
+      const name = view.getUint32(tableRecord('name') + 8)
+      view.setUint16(name + 6 + 10, 0xfff0)
+    })
+    expect(
+      namedInstanceVariations(data, 'Condensed Medium')?.map((variation) => variation.axis)
+    ).toEqual(['wght'])
+    expect(namedInstanceVariations(data, 'Medium')).toEqual([
+      { axis: 'wdth', value: 100 },
+      { axis: 'wght', value: 510 }
+    ])
+  })
+
+  test('ignores fvar tables shorter than their header', () => {
+    const data = patched((view, tableRecord) => view.setUint32(tableRecord('fvar') + 12, 10))
+    expect(namedInstanceVariations(data, 'Medium')).toBeNull()
+  })
+
+  test('ignores fvar tables with undersized axis records', () => {
+    const data = patched((view, tableRecord) => {
+      const fvar = view.getUint32(tableRecord('fvar') + 8)
+      view.setUint16(fvar + 10, 8)
+    })
+    expect(namedInstanceVariations(data, 'Medium')).toBeNull()
+  })
+})
+
+describe('FontManager.namedInstanceVariations', () => {
+  test('resolves variations from the face loaded for a style', () => {
+    const manager = new FontManager()
+    manager.markLoaded('SF Pro', 'Medium', SF_PRO_LIKE)
+    expect(manager.namedInstanceVariations('SF Pro', 'Medium')).toEqual([
+      { axis: 'wdth', value: 100 },
+      { axis: 'wght', value: 510 }
+    ])
+    expect(manager.namedInstanceVariations('SF Pro', 'Bold')).toBeNull()
+  })
+})

tests/fixtures/fonts/Inter-OFL.txt

@@ -0,0 +1,92 @@
+Copyright (c) 2016 The Inter Project Authors (https://github.com/rsms/inter)
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION AND CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.

tests/fixtures/fonts/InterVariable-Latin.ttf

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:768df651a9fd629b069e707a0ffb6880291650c8bd8f997e9fee83c2d6b2197a
+size 166368