/
get-system-ui-family.js
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/
get-system-ui-family.js
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import * as caniuse from 'caniuse-lite';
const NO = 'No';
const APPLE_SYSTEM = 'AppleSystem';
const BLINK_MAC_SYSTEM_FONT = 'BlinkMacSystemFont';
function computePolyfillFlagFromStatus(statusString) {
const flags = [];
const statusArr = statusString.split(' ');
for (const status of statusArr) {
if (status === 'y') {
return [];
} else if (status.includes('n')) {
flags.push(NO);
} else if (status.includes('#1')) { // #1: Supported as the -apple-system value (only on Mac)
flags.push(APPLE_SYSTEM)
} else if (status.includes('#2')) { // #2: Supported as the 'BlinkMacSystemFont' value (only on Mac)
flags.push(BLINK_MAC_SYSTEM_FONT)
}
}
return flags;
}
function generatePolyfillFlags(stats, supportedBrowsers) {
const polyfillFlags = { [APPLE_SYSTEM]: false, [BLINK_MAC_SYSTEM_FONT]: false, [NO]: false };
const visitedStatus = {};
for (const browserAndVersion of supportedBrowsers) {
const [browser, version] = browserAndVersion.split(' ');
const status = stats[browser][version];
if (status === undefined || visitedStatus[status]) {
continue;
}
visitedStatus[status] = true;
const shouldPolyfillFlags = computePolyfillFlagFromStatus(status);
shouldPolyfillFlags.forEach(flag => { polyfillFlags[flag] = true });
}
return polyfillFlags;
}
export default function getSystemUiFamily(supportedBrowsers) {
const { stats } = caniuse.feature(caniuse.features['font-family-system-ui']);
const polyfillFlags = generatePolyfillFlags(stats, supportedBrowsers);
const result = ['system-ui'];
const polyfill =
[
[APPLE_SYSTEM, [
'-apple-system', // macOS, Safari >= 9.2 < 11, Firefox >= 43
]],
[BLINK_MAC_SYSTEM_FONT, [
'BlinkMacSystemFont', // macOS, Chrome < 56
]],
[NO, [
'Segoe UI', // Windows >= Vista
'Roboto', // Android >= 4
'Noto Sans', // Plasma >= 5.5
'Ubuntu', // Ubuntu >= 10.10
'Cantarell', // GNOME >= 3
'Helvetica Neue'
]],
];
return result.concat.apply(result, polyfill.filter(([flag]) => polyfillFlags[flag]).map(v => v[1]));
}