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import type { AdjustFontFallback } from '../../../../../font'
import type { Declaration } from 'postcss'
import postcss from 'postcss'
/**
* The next/font postcss plugin receives the @font-face declarations returned from the next/font loaders.
*
* It hashes the font-family name to make it unguessable, it shouldn't be globally accessible.
* If it were global, we wouldn't be able to tell which pages are using which fonts when generating preload tags.
*
* If the font loader returned fallback metrics, generate a fallback @font-face.
*
* If the font loader returned a variable name, add a CSS class that declares a variable containing the font and fallback fonts.
*
* Lastly, it adds the font-family to the exports object.
* This enables you to access the actual font-family name, not just through the CSS class.
* e.g:
* const inter = Inter({ subsets: ['latin'] })
* inter.style.fontFamily // => '__Inter_123456'
*/
const postcssNextFontPlugin = ({
exports,
fallbackFonts = [],
adjustFontFallback,
variable,
weight,
style,
}: {
exports: { name: any; value: any }[]
fallbackFonts?: string[]
adjustFontFallback?: AdjustFontFallback
variable?: string
weight?: string
style?: string
}) => {
return {
postcssPlugin: 'postcss-next-font',
Once(root: any) {
let fontFamily: string | undefined
const normalizeFamily = (family: string) => {
return family.replace(/['"]/g, '')
}
const formatFamily = (family: string) => {
return `'${family}'`
}
// Hash font-family names
for (const node of root.nodes) {
if (node.type === 'atrule' && node.name === 'font-face') {
const familyNode = node.nodes.find(
(decl: Declaration) => decl.prop === 'font-family'
)
if (!familyNode) {
continue
}
if (!fontFamily) {
fontFamily = normalizeFamily(familyNode.value)
}
familyNode.value = formatFamily(fontFamily)
}
}
if (!fontFamily) {
throw new Error("Font loaders must return one or more @font-face's")
}
// Add fallback @font-face with the provided override values
let adjustFontFallbackFamily: string | undefined
if (adjustFontFallback) {
adjustFontFallbackFamily = formatFamily(`${fontFamily} Fallback`)
const fallbackFontFace = postcss.atRule({ name: 'font-face' })
const {
fallbackFont,
ascentOverride,
descentOverride,
lineGapOverride,
sizeAdjust,
} = adjustFontFallback
fallbackFontFace.nodes = [
new postcss.Declaration({
prop: 'font-family',
value: adjustFontFallbackFamily,
}),
new postcss.Declaration({
prop: 'src',
value: `local("${fallbackFont}")`,
}),
...(ascentOverride
? [
new postcss.Declaration({
prop: 'ascent-override',
value: ascentOverride,
}),
]
: []),
...(descentOverride
? [
new postcss.Declaration({
prop: 'descent-override',
value: descentOverride,
}),
]
: []),
...(lineGapOverride
? [
new postcss.Declaration({
prop: 'line-gap-override',
value: lineGapOverride,
}),
]
: []),
...(sizeAdjust
? [
new postcss.Declaration({
prop: 'size-adjust',
value: sizeAdjust,
}),
]
: []),
]
root.nodes.push(fallbackFontFace)
}
// Variable fonts can define ranges of values
const isRange = (value: string) => value.trim().includes(' ')
// Format the font families to be used in the CSS
const formattedFontFamilies = [
formatFamily(fontFamily),
...(adjustFontFallbackFamily ? [adjustFontFallbackFamily] : []),
...fallbackFonts,
].join(', ')
// Add class with family, weight and style
const classRule = new postcss.Rule({ selector: '.className' })
classRule.nodes = [
new postcss.Declaration({
prop: 'font-family',
value: formattedFontFamilies,
}),
// If the font only has one weight or style, we can set it on the class
...(weight && !isRange(weight)
? [
new postcss.Declaration({
prop: 'font-weight',
value: weight,
}),
]
: []),
...(style && !isRange(style)
? [
new postcss.Declaration({
prop: 'font-style',
value: style,
}),
]
: []),
]
root.nodes.push(classRule)
// Add CSS class that defines a variable with the font families
if (variable) {
const varialbeRule = new postcss.Rule({ selector: '.variable' })
varialbeRule.nodes = [
new postcss.Declaration({
prop: variable,
value: formattedFontFamilies,
}),
]
root.nodes.push(varialbeRule)
}
// Export @font-face values as is
exports.push({
name: 'style',
value: {
fontFamily: formattedFontFamilies,
fontWeight: !Number.isNaN(Number(weight))
? Number(weight)
: undefined,
fontStyle: style && !isRange(style) ? style : undefined,
},
})
},
}
}
postcssNextFontPlugin.postcss = true
export default postcssNextFontPlugin
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