GDK

GDK (GIMP Drawing Kit) is a library that acts as a wrapper around the low-level functions provided by the underlying windowing and graphics systems. GDK lies between the display server and the GTK+ library, handling basic rendering such as drawing primitives, raster graphics (bitmaps), cursors, fonts, as well as window events and drag-and-drop functionality.

Like GTK+, GDK is licensed under the GNU Lesser General Public License (LGPL).

Software architecture

GTK+ is implemented on top of an abstraction layer called GDK, freeing GTK+ from low-level concerns like input gathering and pixel format conversion.

GDK is an important part of GTK+'s portability. Since low-level cross-platform functionality is already provided by GLib, all that is needed to make GTK+ run on other platforms is to port GDK to the underlying operating system's graphics layer. Hence, the GDK ports to the Windows API and Quartz are what makes GTK+ applications run on Windows and OS X, respectively.

Starting with GTK+ 2.8, GDK supports Cairo which should be used with GTK+ 3 instead of GDK's drawing functions.