Ebook: The anatomy of the modern window manager

At the heart of the modern personal computer experience lies the desktop environment, an implementation of the desktop metaphor comprising a variety of programs that together provide common graphical user interface components. Arguably the most complex and, in some systems, the most important component of the desktop environment, is the window manager. A window manager is system software that controls the placement and appearance of windows within a graphical user interface.In this thesis we describe the functioning of top-level window managers. We showcase what common features window managers may consist of, and what their interaction with other system software looks like. In doing so, we will discuss the X Window System[1], along with the Inter-Client Communication Conventions Manual (ICCCM) and Extended Window Manager Hints (EWMH), two standard protocols that define policy on top of the X Window System. Together, they form an environment that facilitates the interoperability between window managers and other, regular programs.As a proof of concept, we provide and discuss kranewm, a complete C++implementation of an ICCCM and EWMH compliant top-level reparenting, tiling window manager, built on top of the X Window System,using Xlib as client-side programming library. With it, we illustrate the low-level functioning of modern top-level window management. Leading up to an extensive demonstration of the product, we review several Agile software development concepts that were applied throughout, before describing the process undergone to realize the implementation.