Adobe has released a monospaced font specifically intended for displaying source code, called Source Code. You can download it on SourceForge, and I will show you how to use it in your favorite IDE on your favorite OS.
1) Download the zip file from SourceForge.
2) Open a terminal and enter the following commands to unzip the font, and recreate your font cache:
mkdir ~/.fonts cd ~/Downloads unzip SourceCodePro_FontsOnly-1.010.zip -d ~/.fonts/ fc-cache -f
3) Restart IntelliJ, open the settings (CTRL-ALT S), and filter for „font“
4) Create a new font scheme by clicking „Save as…“, if you don’t already have a scheme
5) Select „Source Code Pro“, and you’re finished.
So far I like it just a little bit more than the default „DejaVu Sans Mono“, but enough to keep using it. I really like how they used a very minimal design for the lower case i, and that there is a highly noticeable difference between 0 and O.
The blog entry by Paul goes into a lot of detail on what requirements he wanted to adress with his design on a font specifically for source code.