How to show X11 windows with Docker on Mac

I never would have thought that I would need this feature. Up until now, I only used Docker to get some non-UI environments running, like a local PostgreSQL database or an Android build environment for GitLab CI. Right now I am part of a team called ‘Happy Robots’ that works on the final project of Udacity’s <a href="https://www.udacity.com/course/self-driving-car-engineer-nanodegree--nd013" rel="noopener ugc nofollow" target="_blank">Self-Driving Car Engineer Nanodegree</a>. That is: Writing and running <a href="https://github.com/andre-froehlich/CarND-Capstone" rel="noopener ugc nofollow" target="_blank">code</a> on an actual self-driving car! For running the code the 3 Mac users in our 5-person team are using a <a href="https://hub.docker.com/r/bydavy/carnd-capstone/" rel="noopener ugc nofollow" target="_blank">Docker image</a> running the ROS, which is only available for Linux. You might wonder why we would need a UI for running the algorithms, and you are right: We don’t. But we included a dashboard built on the library pygame, which we use to render the track, current waypoints, position of the vehicle, traffic lights and their status and much more later on. This is quite helpful to visualize whether our algorithms behave correctly.  <a href="https://medium.com/@mreichelt/how-to-show-x11-windows-within-docker-on-mac-50759f4b65cb">Read More</a>