The Mutter window manager can function as standalone window manager application for GNOME-like desktops, and serves as the primary window manager for the GNOME Shell desktop, which is an integral part of GNOME 3. Mutter is extensible with plugins and supports numerous visual effects.
The seat now announces invariably the WL_SEAT_CAPABILITY_TOUCH capability, this should be eventually updated as devices come and go.
The creation of MetaWaylandTouchSurface structs is dynamic, attached to the lifetime of first/last touch on the client surface, and only if the surface requests the wl_touch interface. MetaWaylandTouchInfo structs are created to track individual touches, and are locked to a single MetaWaylandTouchSurface (the implicit grab surface) determined on CLUTTER_TOUCH_BEGIN.