Underlying windowing and event handling

# GDK

GDK is the low-level library used by GTK+ to interact with the system for graphics and input devices. Although you will rarely use GDK directly in application code, it contains all the necessary functionality to draw objects and text to the screen and to interact with the user with various input devices.

GDK enables you to access events from keyboards, mice, and other input devices, rather than connect to the high-level signals used in GTK+. GDK also provides low-level routines to access drag and drop and clipboard data from the system. When implementing custom controls, you may need to access these features to implement proper user interaction behavior.

GDK provides other functionality which is needed to implement a complete graphical toolkit like GTK+. Since GDK acts as a platform abstraction, allowing GTK+ to run under multiple environments, it provides an API for all of the system functionality needed by GTK+. This includes information about multi-head displays, resolution and color depth, colormaps, and cursors.

You should use GDK whenever you need low-level access to the underlying windowing system, including low-level access to events, windows, and the clipboard. Using GDK for these tasks ensures that your code is portable and integrates with the rest of your GTK+ code. The simple drawing routines in GDK should generally not be used. Instead, you should use the extensive functionality provide by Cairo.

GDK Reference Manual