1. Overview

This extension provides arbitrary window and border shapes within the X11 protocol.

The restriction of rectangular windows within the X protocol is a significant limitation in the implementation of many styles of user interface. For example, many transient windows would like to display a "drop shadow" to give the illusion of 3 dimensions. As another example, some user interface style guides call for buttons with rounded corners; the full simulation of a nonrectangular shape, particularly with respect to event distribution and cursor shape, is not possible within the core X protocol. As a final example, round clocks and nonrectangular icons are desirable visual addition to the desktop.

This extension provides mechanisms for changing the visible shape of a window to an arbitrary, possibly disjoint, nonrectangular form. The intent of the extension is to supplement the existing semantics, not replace them. In particular, it is desirable for clients which are unaware of the extension to still be able to cope reasonably with shaped windows. For example, window managers should still be able to negotiate screen real-estate in rectangular pieces. Toward this end, any shape specified for a window is clipped by the bounding rectangle for the window as specified by the window's geometry in the core protocol. An expected convention would be that client programs expand their shape to fill the area offered by the window manager.