Added support Sec-CH-UA-Form-Factors header for ClientHints

[sanchezzzhak]

Specs: https://wicg.github.io/ua-client-hints/#sec-ch-ua-form-factors
form factor support for chrome 124+ https://chromestatus.com/feature/5162545698045952

[sanchezzzhak]

maybe we should add examples to the documentation for client-hints?

For example, through JS, we can get them like this:

function getHints() {
    return new Promise((resolve, reject) => {
      if (!navigator.userAgentData) {
        return resolve({})
      }
      let requestHints = [
        'brands',
        'mobile',
        'platform',
        'platformVersion',
        'architecture',
        'bitness',
        'wow64',
        'model',
        'formFactors',
        'uaFullVersion',
        'fullVersionList'];

      navigator.userAgentData.getHighEntropyValues(requestHints).then((result) => {
        resolve(JSON.parse(JSON.stringify(result)))
      }).catch(() => {
        resolve({});
      });
    })
  }

getHints().then(data =>console.log(data)) 

[sgiehl]

@sanchezzzhak Based on the definition formFactors is a sf-list. So it can contain multiple comma separated values. In theory something like "Tablet","EInk" would be a valid value. So we would actually need to handle that as array and not as string. Or did I misinterpret the definition 🤔

[liviuconcioiu]

For reference, Android tablets are reporting as Desktop, but detection works. 🎉

[sanchezzzhak]

@sgiehl yes there should be an array.

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I think the form factor based on the user agent string, since there is no prefix (Table|Mobile|VR|TV|XR) is set by default to Desktop

[sgiehl]

Looks good to me now.