Help about font driver in FreeType

hello, I'm a newbie. I'm confused by a freetype font driver. Wish you can 
help me !
I had wrotten a font driver through Freetype 2.1.3, which served as my own 
private style outline fonts. Then I used "make" and "make install" and then 
use "startx" to open KDE and found my fonts's name have been shown in font 
lists of some applications such as Kworld, kcalc, that's ok. but things 
happed that the application can't display strings using my fonts which I 
choose from font lists! Who can give me an explian about this? 
And I'm confused by the fowlling questions: As I knowed that there are 
freetype's share lib in directory /usr/lib, but when you start x using 
"startx", X also load "libfreetype.a" in other directory such as 
/usr/lib/X11/modules/fonts/. I want to know that which freetype be called 
when I display a string in the KDE's application. who can give me a 
flowchart about this call? Thanks very much!

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