) window attribute is not limited to
communicating with window managers. It may be used for attaching
arbitrary data to a window. It is important to note that getting
window properties is expensive, as it requires a round trip to the X
server. However properties are an effective way for multiple
applications in separate address spaces to communicate.
As described in pxl-win-atts, the name argument N of a property attribute may be any atom. The value argument V may be a pixmap, a colormap, a cursor, a font, an integer, a pixmap, an atom, a visual term, a window, or one of the following terms: