Users of Windows Classic and high contrast themes can use the experiences enabled by desktop composition such as Windows Flip, automatic scaling for high resolution (DPI) scaling, thumbnail previews, and full screen magnifier. With Windows 8, desktop composition is enabled for all themes. In addition, in these earlier versions of Windows, app developers must write and maintain multiple code paths – one where desktop composition is enabled and another where desktop composition is disabled. Hence users of Windows Classic and high contrast themes cannot use experiences enabled by desktop composition such as Windows Flip, automatic scaling for high resolution (DPI) scaling, thumbnail Preview and full screen magnifier. In Windows Vista and Windows 7, desktop composition is enabled only with the AERO Glass Theme. In addition to experiences enabled in Windows 7, now DWM desktop composition enables desktop composition for all themes, support for Stereoscopic 3D, and management, separation, and protection of the experience with Windows Store apps. As in Windows 7, DWM is used to compose the desktop.
In Windows 8, Desktop Window Manager (DWM) is always ON and cannot be disabled by end users and apps. Servers – Windows Server 2012 Description
