64 lines
1.9 KiB
Plaintext
64 lines
1.9 KiB
Plaintext
// @flow
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import getValueAndUnit from './getValueAndUnit'
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import PolishedError from '../internalHelpers/_errors'
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const defaultFontSize = 16
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function convertBase(base: string | number): number {
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const deconstructedValue = getValueAndUnit(base)
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if (deconstructedValue[1] === 'px') {
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return parseFloat(base)
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}
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if (deconstructedValue[1] === '%') {
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return (parseFloat(base) / 100) * defaultFontSize
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}
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throw new PolishedError(78, deconstructedValue[1])
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}
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function getBaseFromDoc(): number {
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/* eslint-disable */
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/* istanbul ignore next */
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if (typeof document !== 'undefined' && document.documentElement !== null) {
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const rootFontSize = getComputedStyle(document.documentElement).fontSize
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return rootFontSize ? convertBase(rootFontSize) : defaultFontSize
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}
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/* eslint-enable */
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/* istanbul ignore next */
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return defaultFontSize
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}
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/**
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* Convert rem values to px. By default, the base value is pulled from the font-size property on the root element (if it is set in % or px). It defaults to 16px if not found on the root. You can also override the base value by providing your own base in % or px.
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* @example
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* // Styles as object usage
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* const styles = {
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* 'height': remToPx('1.6rem')
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* 'height': remToPx('1.6rem', '10px')
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* }
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*
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* // styled-components usage
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* const div = styled.div`
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* height: ${remToPx('1.6rem')}
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* height: ${remToPx('1.6rem', '10px')}
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* `
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*
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* // CSS in JS Output
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*
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* element {
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* 'height': '25.6px',
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* 'height': '16px',
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* }
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*/
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export default function remToPx(value: string | number, base?: string | number): string {
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const deconstructedValue = getValueAndUnit(value)
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if (deconstructedValue[1] !== 'rem' && deconstructedValue[1] !== '') {
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throw new PolishedError(77, deconstructedValue[1])
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}
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const newBase = base ? convertBase(base) : getBaseFromDoc()
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return `${deconstructedValue[0] * newBase}px`
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}
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