anchor.diff:    (when (and (boundp '*current-framebuffer*)
                *current-framebuffer*)
       (let ((fb-addr (framebuffer-base-address *current-framebuffer*)))
  -      (%%bitset-row (convert-to-pmap-address fb-addr)
  -                    #xFFFF0000
  -                    (framebuffer-width *current-framebuffer*))
  +      (funcall (framebuffer-fill-fn *current-framebuffer*)
  +               (convert-to-pmap-address fb-addr)
  +               #xFFFF0000
  +               (framebuffer-width *current-framebuffer*))
         (funcall (framebuffer-damage-fn *current-framebuffer*)
                  0 0
                  (framebuffer-width *current-framebuffer*) 1
  
positive.code:   (sys.lap-x86:movs32)
    (sys.lap-x86:ret))
  
  #+arm64
  (sys.int::define-lap-function %%bitblt-row ((to-base from-base ncols))
    (mezzano.lap.arm64:add :x12 :xzr :x0 :asr #.sys.int::+n-fixnum-bits+) ; to-storage
    (mezzano.lap.arm64:add :x11 :xzr :x1 :asr #.sys.int::+n-fixnum-bits+) ; from-storage
    (mezzano.lap.arm64:add :x5 :xzr :x2 :asr #.sys.int::+n-fixnum-bits+) ; ncols
  
negative.code:                            (* (1- (framebuffer-height *current-framebuffer*))
                                (framebuffer-pitch *current-framebuffer*))
                             0)
                         (* light-offset (framebuffer-bytes-per-pixel *current-framebuffer*))))
             (colour (if (light-state light)
                         (light-colour light)
                         0)))
        (when (<= (+ light-offset 32) (framebuffer-width *current-framebuffer*))
          (funcall (framebuffer-fill-fn *current-framebuffer*)
                   (convert-to-pmap-address fb-addr)
                   colour
                   32)
          (funcall (framebuffer-damage-fn *current-framebuffer*)
                   0 0
                   (framebuffer-width *current-framebuffer*) 1
  