The GNOME canvas is an engine for structured graphics that offers a rich imaging model, high performance rendering, and a powerful, high-level API. It offers a choice of two rendering back-ends, one based on Xlib for extremely fast display, and another based on Libart, a sophisticated, antialiased, alpha-compositing engine. Applications have a choice between the Xlib imaging model or a superset of the PostScript imaging model, depending on the level of graphic sophistication required.
A canvas is a window with a collection of graphical items inside it. The canvas is designed to work as a general-purpose display engine for applications. It provides simple primitive item types such as rectangles, ellipses, and text. These can be used by applications with modest graphics needs. Applications can also define their custom canvas item types to provide sophisticated displays.
The canvas takes care of all drawing operations on its items so that it will never flicker. Canvas items are normal GTK+ objects, and they emit signals based on events from the mouse or keyboard. This allows the programmer to implement interactive behavior for the items very easily.