Desktop Window Manager

The Desktop Composition Engine (or DCE) is a theme rendering engine used in early builds of Windows Longhorn. It is synchronized with WinFS, Avalon, and other internal Windows databases, as well as providing visual effects.

History
The Desktop Composition Engine is first present starting with build 3683, but in a buggy state that only renders windows transparency. Starting from build 3706 through build 4005, a new twirling effect when minimizing or closing windows is added, and a user interface was included to allow the user to enable DCE on boot or via dynamic control.

Throughout Milestone 5, Lab06 builds such as build 4015 and build 4018 were known to have additional DCE effects, including graphical animations and flapping windows while dragging. Despite these animations, other labs used only window transparency effects. Eventually, starting with Milestone 6, the Desktop Composition Engine was reworked to enable a new glass border theme, which would be the forerunner to the Windows Aero theme. While earlier builds have a bug in the DCE which causes it to use CPU processing instead of hardware processing, it wouldn't be until build 4039 to have a working Windows Aero theme.

Desktop Composition Engine remained with most builds until build 4053. Eventually, build 4066 replaced the DCE with Desktop Window Manager.