Programs must be prepared to cooperate with any type of window manager or with none at all. Unlike citizens, the window manager has rights but not responsibilities. In fact, it does not even require a window manager to be present at all:

Its developers have tried to make X itself as free of window management or user interface policy as possible.

X is somewhat unusual in that it does not mandate a particular type of window manager. This decision is to thank for the wild diversity of X window managers we see today. Unlike other windowing systems such as Microsoft Windows or Mac OS X, X does not dictate a window manager or how a window manager should behave. Let’s start with an examination of the role of the window manager in a modern Linux/BSD desktop environment. In addition, its chapter 16 also covers the basics of window management. Since you could buy the book plus shipping for less than the price of a cup of coffee, I strongly recommend it to anyone interested in learning more about X. Despite its age, it remains amazingly relevant and is the best available introductory text to the internals of X, which has not changed over the past two decades as much as you’d think. I will be quoting quite heavily from the seminal Xlib Programming Manual (3rd Ed, 1994) by Adrian Nye and published by O’Reilly. In this series of posts, I hope to demystify how window managers work, and how you might go about writing one yourself. Hence, almost 30 years since the first X window manager, we still argue over the merits of different window managers, and new window managers continue to reinvent how we interact with our digital world. It is not an exaggeration to say that they define to a large degree our day-to-day user experience, as they are responsible for deciding how individual windows look, move around, react to input, and organize themselves.

Window managers are one of the core components of the modern Linux/BSD desktop.

Window Manager Technical Notes How X Window Managers Work, And How To Write One (Part I).

Windows window organizer