anchor.diff:             (type fixnum to-offset))
     (setf (aref to to-offset) source))
   
  -(declaim (inline %%xor-one-argb8888-argb8888))
   (defun %%xor-one-argb8888-argb8888 (source to to-offset)
     (declare (optimize speed (safety 0) (debug 0))
              (type (unsigned-byte 32) source)
  
positive.code: 
  ;;; Final blending functions.
  
  (declaim (inline %%xor-one-argb8888-argb8888))
  (defun %%set-one-argb8888-argb8888 (source to to-offset)
    (declare (optimize speed (safety 0) (debug 0))
             (type (unsigned-byte 32) source)
  
negative.code: 
  ;; Line traversal functions.
  
  (defun %bitblt-line (blender to to-offset ncols from from-offset)
    (declare (optimize speed (safety 0) (debug 0))
             (type function blender)
             (type fixnum to-offset ncols from-offset)
             (type (simple-array (unsigned-byte 32) (*)) to from))
    (loop for i fixnum below ncols do
      (funcall blender (aref from from-offset) to to-offset)
      (incf to-offset)
      (incf from-offset)))
  
  (defun %bitset-line (blender to to-offset ncols colour)
    (declare (optimize speed (safety 0) (debug 0))
             (type function blender)
             (type fixnum to-offset ncols)
             (type (simple-array (unsigned-byte 32) (*)) to)
             (type (unsigned-byte 32) colour))
    (loop for i fixnum below ncols do
      (funcall blender colour to to-offset)
      (incf to-offset)))
  
  (defun %bitset-mask-1-line (blender to to-offset ncols mask mask-offset colour)
    (declare (optimize speed (safety 0) (debug 0))
             (type function blender)
  