The Erlang observer looks a bit bizarre in OSX when using dark-mode. This guide helps fixing it.

The Erlang observer looks a bit bizarre on OSX Mojave or newer when using dark-mode.
This has been annoying since I’ve been switching from my favorite dark-mode to the light one to use the observer.
The following is an image of how it looks:

Observer looking bad in Dark Mode

Tonight, I took some time to research how this could be improved and stumbled upon the issue ERL-921 in the Erlang/OTP bug tracker.
This lead me to check the WXWidgets changelog at and dark-mode support was introduced in version 3.1.3: (released 2019-10-28).
The default version that comes in Homebrew is wxMac 3.0.5 for OSX Catalina. Heh, here is the problem!

Heading to, 3.1.4 is the latest release as of today’s date.
We are going to edit the Homebrew formulae located at /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/wxmac.rb with our preferred editor or by running brew edit wxmac.
These are the changes we are going to perform:

  1. Change url with the path to the version we want to install: “”.
  2. Change sha256 with the file sha256 checksum, in version 3.1.4 case it is “3ca3a19a14b407d0cdda507a7930c2e84ae1c8e74f946e0144d2fa7d881f1a94”.
  3. Add "--enable-compat28", to the args inside def install in the formulae. This one took me a bit of reading to make it work, but always the great OTP documentation helped

Now we can install the new wxmac version from the edited formulae and run brew upgrade wxmac.

Went to compile Erlang/OTP with my favorite tool named kerl:

$ kerl build 23.0 23.0
$ kerl install 23.0

And after that, running the observer worked nicely with dark-mode:

Observer looking great in Dark Mode

That’s all folks! Hope this helps some of you.