I have Eclipse installed in a Linux machine. A while ago I did a Linux update and it messed up the fonts on the entire system. All the fonts got larger. So, I went all over the place resizing the fonts for each application.
Guess what?! On the next Linux update, the fonts got back to normal. However, I had to go back and undo all the font resizing that I had previously done on every application. So, when it came time to reset the fonts in Eclipse, I couldn't remember exactly what I did. I went to the following location:
Window > Preferences > General > Appearance > Colors and Fonts > Basic > Text Font > Edit
No matter what I did on this setting, the font remained the same.
I finally figured out what the problem was. I had also resized the fonts on the following location:
Window > Preferences > General > Appearance > Colors and Fonts > Structured Text Editors > Structured Text Editor Text Font (overrides default: Text Font) > Edit
Once I edited this setting, the fonts on Eclipse went back to normal.