Setting chrome devtool's "emulation/default-background-color-override"

[carlhu]

Etaoin's api is beautifully designed: thank you so much for sharing this.

I'd like to use the api's element capture api (which works great) except with transparent background. When I use the devtool protocol directly, setting the emulation/set-default-background-color-override to some color with alpha 0 works great. But I can't figure out how to use etaoin to do execute a (in Selenium's terms) a cdp command. Can you offer any guidance?

If it helps, here is the java from their docs:

driver.executeCdpCommand("Emulation.setDefaultBackgroundColorOverride", color);

[lread]

@carlhu, I too am enjoying Etaoin (thanks @igrishaev!).

And I too was wondering how to take a screenshot with a transparent background.
I searched around and found this Python example on StackOverflow:

from selenium import webdriver
import json

def send(cmd, params={}):
  resource = "/session/%s/chromium/send_command_and_get_result" % driver.session_id
  url = driver.command_executor._url + resource
  body = json.dumps({'cmd':cmd, 'params': params})
  response = driver.command_executor._request('POST', url, body)
  if response['status']: raise Exception(response.get('value'))
  return response.get('value')

options = webdriver.ChromeOptions()
options.add_argument("disable-gpu")
options.add_argument("disable-infobars")

driver = webdriver.Chrome(chrome_options=options)
driver.get("http://www.bbc.co.uk/news")

# take screenshot with a transparent background
send("Emulation.setDefaultBackgroundColorOverride", {'color': {'r': 0, 'g': 0, 'b': 0, 'a': 0}})
driver.get_screenshot_as_file(r"C:\temp\screenshot.png")
send("Emulation.setDefaultBackgroundColorOverride")  # restore

The etaion API includes an execute, so I had it do what I found to be the interesting parts of the above Python like so:

(etaoin/execute {:driver driver
                 :method :post
                 :path [:session (:session driver) "chromium" "send_command_and_get_result"]
                 :data {:cmd "Emulation.setDefaultBackgroundColorOverride"
                        :params {:color {:r 0 :g 0 :b 0 :a 0}}}})

Which I follow with my particular screenshot request:

(etaoin/screenshot-element driver
                           {:tag :div :class :wrapper}
                           (str target-dir "/" github-id ".png"))

And it seems to work!