It seems scintilla or teh font is broken, if I change it in the editor settings it works correctly.
Your font ("Ubuntu" ?) is replaced by "Cantarell" (system default) and this does (reproducible) not work.
The cause seems to be a problem with the "fi" in define which is recognized as one letter and not as two, it might in fact be one special character in the editor.
I think there was similar issue before with some fonts (at least on Ubuntu), but I'm not absolutely sure about this.
In general it is better to use a monospaced font instead a proportional font for programming.