Expose API to enable mobile emulation mode

[d4rky-pl]

From what I see in the library there's only one call to setDeviceMetricsOverride that sets mobile: false.

It would be great if there was an exposed API to enable mobile emulation and manage width and height of the viewport dynamically.

[alagos]

FWIW, I've added a mobile user agent to emulate it:

agent = 'Mozilla/5.0 (Linux; Android 7.0.0; Pixel Build/Unknown;) AppleWebKit/537.36.0 (KHTML, like Gecko) Chrome/60.0.0.0 Mobile Safari/537.36.0'
browser.headers.set("User-Agent" => agent)

Probably isn't the same, but it worked for me.

[duncan-bayne]

Looking at this now, in order to facilitate rubycdp/cuprite#216.

Weirdly, simply setting mobile: true in the call to setDeviceMetricsOverride doesn't work - the mobile emulation isn't enabled, although other overrides (e.g. size) are set.

[duncan-bayne]

Tracking the individual CDP call:

{
  :method => "Emulation.setDeviceMetricsOverride",
  :params => {
    :width => 2000,
    :height => 1000,
    :deviceScaleFactor => 0,
    :mobile => true
  },
  :id => 21,
  :sessionId => "7CA1F8989530B558F771E702BF661CD4"
}

... it doesn't result in any errors, but also, mobile emulation doesn't get enabled. This is true of headless and non-headless. Interestingly if I disable headless and manually interact with the browser, I can enable mobile emulation in dev tools as usual.

[d4rky-pl]

@duncan-bayne I think the CDP call doesn't enable the same UI as the manual click on the devtools but it does indeed enable mobile emulation. You need to enable touch events separately though.

[duncan-bayne]

Ah! That'll be it, @d4rky-pl! Because the spec I wrote to test whether mobile emulation had been enabled works by checking that touch has been enabled.

Edited: hey, neat, emoji substitution is broken in GitHub's editor on Firefox mobile :/