@Yue: if the font is truetype, it may have a .def file too, this is where the name of the font should be.
For a screenpack I made with a truetype font, I placed both .def and .ttf files into the "fonts" folder:
When you open the def file, this is what shows up:
Spoiler, click to toggle visibilty
^ see if the name here correspond to the name of the font.