From uGFX Wiki
The µGFX library is fully in-source code documented using doxygen.
The API reference of the uGFX library can be found here.
What is doxygen?
From Wikipedia, the free encyclopedia:
Doxygen is a documentation generator, a tool for writing software reference documentation. The documentation is written within code, and is thus relatively easy to keep up to date. Doxygen can cross reference documentation and code, so that the reader of a document can easily refer to the actual code.