IDirectDrawSurface3::IsLost

DDraw vtable[24] → HRESULT

IDirectDrawSurface3::IsLost is a method of the COM interface IDirectDrawSurface3 in DirectDraw. Its function pointer sits at vtable index 24 — the zero-based slot in that interface's virtual method table, counted from QueryInterface and including every entry inherited from a base interface. It takes no parameters and returns HRESULT.

COM methods are reached through that table rather than by an exported name, so the slot index is what a wrapper, an interface hook or a disassembly listing has to resolve against.