XGetWindowProperty

XGetWindowProperty is a function provided by the X Window System, a windowing system protocol that forms the basis for most modern Unix-like graphical user interfaces. This function is used to retrieve properties associated with a specific window. In the X Window System, windows can have arbitrary data associated with them, which are known as properties. These properties are identified by a unique atom.

The XGetWindowProperty function allows an X client, which is typically an application running on the display server, to query the server for the value of a particular property on a given window. It takes several arguments, including the display connection, the window ID, the property atom to retrieve, the starting offset within the property, the number of elements to retrieve, and a flag indicating whether to retrieve only if the property type matches. The function returns the data type of the property, the number of elements retrieved, and a pointer to the actual data. The data is usually returned as a sequence of 32-bit, 16-bit, or 8-bit integers, depending on the property's defined format.

This function is fundamental for inter-process communication within the X Window System. Applications use XGetWindowProperty to access information such as window titles, window manager hints, or other metadata that windows can expose to other clients. For example, a window manager might use it to get the WM_NAME property to display a window's title in its title bar. The data retrieved by XGetWindowProperty must be freed by the client using XFree.