Loading fonts on the fly from C

[Chase]

I'm porting an app from Mac OS X to linux.

There is an OS X API that I use to load my own font on the fly as the  
app starts up.  The function is FMActivateFonts().

When I start up, I check to make sure that it's not already loaded.   
If it's not, I load it.  When the app quits, the font is unloaded  
automatically.

What is the Linux function for loading a font this way?

Thanks.

- Chase