Arduino editor problem

Hi, in my editor the code/textfield has a blue/grey background, and is uneditable. Did I enable some strange mode or is this a bug?

I can still compile and change .ino files using another texteditor.

I'm running macOS Sierra 10.12.4

I tried a restart of my laptop, and a reinstallation of arduino IDE. No changes. Any tips are greatly appreciated!

Do this:
File > Preferences > Use external editor (uncheck) > OK