Screenshots taken in 1000px viewport are 800px wide in Docker + Chrome + Headless

[steveharrison]

Current behavior:

When I set the viewport to 1000x600px and then take a screenshot, the resulting screenshot is 800x600px wide. This only happens when running inside Docker.

Desired behavior:

I expect the screenshot to be 1000px wide.

I've read @brian-mann's post about issues with taking screenshots larger than 1280x720px, but 1000x600px is within these dimensions.

Test code to reproduce

1. Checkout this repository: https://github.com/steveharrison/cypress-viewport-test/.
2. Install dependencies with npm i.
3. Start the test server with npm start, which will fire up a server at http://localhost:9000.
4. Ensure Docker for Mac is running and then run npm run test-d (which runs docker run -it -v $PWD:/cypress -w /cypress --entrypoint=cypress cypress/included:3.8.2 run --config baseUrl=http://host.docker.internal:9000 --headless --browser chrome).
5. Check the resolution of screenshots/main.spec.js/Cypress Viewport Test -- works.png.

Versions

• Cypress 3.8.2 (running in Docker using cypress/included:3.8.2)
• Docker for Mac 2.2.0.0
• macOS 10.12.6
• Node 13.6.0 (running in nvm and used for the project, not in Docker)

[jennifer-shehane]

Duplicate of #6210