How can font-ids of internal fonts be retrieved? An example demonstrates the use of the OpenGL Wrapper (bgl) to print text, it loads a font from an external file.

How can a font id of an internaly available font queried?

blf.position(font_id, (width * 0.2), (height * 0.3), 0)
blf.size(font_id, 50, 72)
blf.draw(font_id, "Hello World")
There is no API to query internal fonts, the documentation says that 0 as font-id can be used for the default font.