selenium webdriver - How can I set the browser window size when using `google-chrome --headless`?

Question

I tried setting the browser size on Chrome --headless by using Selenium WebDriver commands.

I get this WebDriver error:

      - Failed: unknown error: cannot get automation extension
from unknown error: page could not be found: chrome-extension://aapnijgdinlhnhlmodcfapnahmbfebeb/_generated_background_page.html
  (Session info: headless chrome=58.0.3029.81)
  (Driver info: chromedriver=2.29.461571 (8a88bbe0775e2a23afda0ceaf2ef7ee74e822cc5),platform=Linux 4.4.0-72-generic x86_64) (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 10.07 seconds
Build info: version: '3.3.1', revision: '5234b32', time: '2017-03-10 09:04:52 -0800'
System info: host: '826f6a766112', ip: '172.17.0.2', os.name: 'Linux', os.arch: 'amd64', os.version: '4.4.0-72-generic', java.version: '1.8.0_121'
Driver info: org.openqa.selenium.chrome.ChromeDriver
Capabilities [{applicationCacheEnabled=false, rotatable=false, mobileEmulationEnabled=false, networkConnectionEnabled=false, chrome={chromedriverVersion=2.29.461571 (8a88bbe0775e2a23afda0ceaf2ef7ee74e822cc5), userDataDir=/tmp/.org.chromium.Chromium.cuymDL}, takesHeapSnapshot=true, pageLoadStrategy=normal, databaseEnabled=false, handlesAlerts=true, hasTouchScreen=false, version=58.0.3029.81, platform=LINUX, browserConnectionEnabled=false, nativeEvents=true, acceptSslCerts=true, locationContextEnabled=true, webStorageEnabled=true, browserName=chrome, takesScreenshot=true, javascriptEnabled=true, cssSelectorsEnabled=true, unexpectedAlertBehaviour=}]
Session ID: 9569e5ebd8f7540ce510b20647443baf

Answer 1

I found it. Simply pass the --window-size command line argument to Google Chrome, for example --window-size=1920,1080.

In a Protractor configuration this would look like this:

capabilities: {
    browserName: 'chrome',
    chromeOptions: {
        args: ['headless', 'window-size=1920,1080']
    }
}

The cool thing is that the windows size is not limited to the current display. It is truly headless, meaning it can be as large as needed for the tests.

Java code:

options.addArguments("window-size=1920,1080");

I expand a bit more on this in Headless protractor not sharding tests.