Sawfish

Sawfish is an extensible window manager using an Emacs Lisp-like scripting language--all window decorations are configurable, the basic idea is to have as much user-interface policy as possible controlled through the Lisp language. Despite this extensibility its policy is currently very minimal compared to most window managers. Its aim is simply to manage windows in the most flexible and attractive manner possible. As such it does not implement desktop backgrounds, applications docks, or other things that may be achieved through separate applications. Also, most received events are exported to the Lisp environment through key-bindings'' and hooks, similar to in Emacs. These events include pointer behaviour and many internal X11 events (enter/leave, focus-in/focus-out, map/unmap, etc..)