GTK(GIMP Toolkit)是一套跨多种平台的图形工具包,按LGPL许可协议发布的。虽然最初是为GIMP写的，但目前已发展为一个功能强大、设计灵活的一个通用 图形库。特别是被GNOME选中使得GTK+广为流传，成为Linux下开发图形界面的应用程序的主流开发工具之一，当然GTK+并不要求必须在 Linux上，事实上，目前GTK+已经有了成功的windows版本。
1. gdk-pixbuf was separated into its own module.
2. GTK+ and GDK gained a considerable number of accessors, and more APIs that are slated for removal in GTK+ 3 were marked as deprecated....
3. Several new Cairo-related functions were introduced.
4. More details can be found in the changelogs of the 2.21.x development releases.
5. Against the last development release, the gobject-introspection requirement was lowered, a failure to build without XComposite was fixed, and translations were updated