GTK、GDK、GLIB三者的关系
http://blog.csdn.net/wtz1985/article/details/2915017
GTK+ 简介

http://zetcode.com/tutorials/gtktutorial/chinese/introduction/

GDK (GIMP Drawing Kit) is a computer graphics library that acts as a wrapper
around the low-level drawing and windowing functions provided by the
underlying graphics system.
https://developer.gnome.org/gdk/
http://en.wikipedia.org/wiki/GDK

GTK在Linux的Gnome桌面下的层级关系。换句话说如果你能把GDK移植到别的平台，那么GTK只需要很小的efforts也可以移植到对应的平台上去。

Gnome
GTK+ | QT
GDK

X Server

BTW,编译GTK代码的方法：

gcc -Wall helloworld.c -o helloworld $(pkg-config –cflags –libs gtk+-2.0)