With this image you can simply download the mixxx source code and run a container to compile and run the program, yihaa!
Letting docker containers access your Xwindows is always a bit of a security tradeof.
Bearing this in mind as long as you are running stuff on your own computer where to
only you have access to, I would say it is pretty OK. You can read about different ways
to achieve this and their pros and cons:
In this 'lean' version I leave the source code itself outside the image to be linked in
at run time. Thus before you will boot up the container you need to have some directory
somewhere with your cloned mixxx source code from github.