I set up my retina MacBook Pro with Linux and I am unable to find a suitable solution to work with the Processing IDE in a productive way as the interface of the IDE is rather small.

Sketches do not scale as well, but this is a limitation I can work around.

As the recognition of pixel densities in Linux appears to be somewhat complicated, the introduction of the possibility to manually set the DPI scaling factor via the settings dialogue or a config file could be a practical solution.

In the meantime any kind of workaround would probably do.

Here is a screenshot showing Processing next to a (patched) Arduino IDE with 200% scaling factor: