code: func StencilOpSeparate(face uint32, sfail uint32, dpfail uint32, dppass uint32) {
  	syscall.Syscall6(gpStencilOpSeparate, 4, uintptr(face), uintptr(sfail), uintptr(dpfail), uintptr(dppass), 0, 0)
  }
docs: // set front and/or back stencil test actions