KWin Mission Statement

User Perspective

KWin is an easy to use, but flexible, composited Window Manger for windowing systems on Linux. Its primary usage is in conjunction with a Desktop Shell (e.g. KDE Plasma Desktop). KWin is designed to go out of the way; users should not notice that they use a window manager at all. Nevertheless KWin provides a steep learning curve for advanced features, which are available, if they do not conflict with the primary mission. KWin does not have a dedicated targeted user group, but follows the targeted user group of the Desktop Shell using KWin as it's Window Manager.

What KWin is not

KWin is not a standalone window manager (c.f. openbox) and does not provide any functionality belonging to a Desktop Shell.
KWin is not a replacement for Window Managers designed for use with a specific Desktop Shell (e.g. GNOME Shell)
KWin is not a minimalistic Window Manager
KWin is not designed for use without compositing or for X11 network transparency, though both are possible.

Developer Perspective

A new Feature can only be added to KWin if:

it does not violate the primary missions as stated in User Perspective
it does not introduce instabilities
it is maintained, that is bugs are fixed in a timely manner (second next minor release) if it is not a corner case.
it works together with all existing features
it supports both single and multi screen (xrandr)
it adds a significant advantage
it is feature complete, that is supports at least all useful features from competitive implementations
it is not a special case for a small user group
it does not increase code complexity significantly

All new added features are under probation, that is if any of the non-functional requirements as listed above do not hold true in the next two feature releases, the added feature will be removed again.

The same non functional requirements hold true for any kind of plugins (effects, scripts, etc.). It is suggested to use scripted plugins and distribute them separately.