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102 lines
2.7 KiB
JavaScript
102 lines
2.7 KiB
JavaScript
'use strict'
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/**
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* Font RegExp helpers.
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*/
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const weights = 'bold|bolder|lighter|[1-9]00'
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const styles = 'italic|oblique'
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const variants = 'small-caps'
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const stretches = 'ultra-condensed|extra-condensed|condensed|semi-condensed|semi-expanded|expanded|extra-expanded|ultra-expanded'
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const units = 'px|pt|pc|in|cm|mm|%|em|ex|ch|rem|q'
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const string = '\'([^\']+)\'|"([^"]+)"|[\\w\\s-]+'
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// [ [ <‘font-style’> || <font-variant-css21> || <‘font-weight’> || <‘font-stretch’> ]?
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// <‘font-size’> [ / <‘line-height’> ]? <‘font-family’> ]
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// https://drafts.csswg.org/css-fonts-3/#font-prop
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const weightRe = new RegExp(`(${weights}) +`, 'i')
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const styleRe = new RegExp(`(${styles}) +`, 'i')
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const variantRe = new RegExp(`(${variants}) +`, 'i')
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const stretchRe = new RegExp(`(${stretches}) +`, 'i')
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const sizeFamilyRe = new RegExp(
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`([\\d\\.]+)(${units}) *((?:${string})( *, *(?:${string}))*)`)
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/**
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* Cache font parsing.
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*/
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const cache = {}
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const defaultHeight = 16 // pt, common browser default
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/**
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* Parse font `str`.
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*
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* @param {String} str
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* @return {Object} Parsed font. `size` is in device units. `unit` is the unit
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* appearing in the input string.
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* @api private
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*/
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module.exports = str => {
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// Cached
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if (cache[str]) return cache[str]
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// Try for required properties first.
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const sizeFamily = sizeFamilyRe.exec(str)
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if (!sizeFamily) return // invalid
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// Default values and required properties
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const font = {
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weight: 'normal',
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style: 'normal',
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stretch: 'normal',
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variant: 'normal',
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size: parseFloat(sizeFamily[1]),
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unit: sizeFamily[2],
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family: sizeFamily[3].replace(/["']/g, '').replace(/ *, */g, ',')
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}
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// Optional, unordered properties.
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let weight, style, variant, stretch
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// Stop search at `sizeFamily.index`
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const substr = str.substring(0, sizeFamily.index)
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if ((weight = weightRe.exec(substr))) font.weight = weight[1]
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if ((style = styleRe.exec(substr))) font.style = style[1]
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if ((variant = variantRe.exec(substr))) font.variant = variant[1]
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if ((stretch = stretchRe.exec(substr))) font.stretch = stretch[1]
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// Convert to device units. (`font.unit` is the original unit)
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// TODO: ch, ex
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switch (font.unit) {
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case 'pt':
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font.size /= 0.75
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break
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case 'pc':
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font.size *= 16
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break
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case 'in':
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font.size *= 96
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break
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case 'cm':
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font.size *= 96.0 / 2.54
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break
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case 'mm':
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font.size *= 96.0 / 25.4
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break
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case '%':
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// TODO disabled because existing unit tests assume 100
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// font.size *= defaultHeight / 100 / 0.75
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break
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case 'em':
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case 'rem':
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font.size *= defaultHeight / 0.75
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break
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case 'q':
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font.size *= 96 / 25.4 / 4
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break
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}
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return (cache[str] = font)
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}
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