anchor.diff:      (when (and (> nrows 0)
                  (> ncols 0))
         (sys.int::%bitset nrows ncols val to-array to-row to-col))))
  -
  -(defun bitblt-test ()
  -  (let ((src (make-array (list 64 32) :element-type '(unsigned-byte 32))))
  -    (sys.int::%bitset 64 32 (make-colour '(0.8 0.5 0.2)) src 0 0)
  -    (bitblt 64 32 src 0 0 sys.int::*bochs-framebuffer* 500 500)
  -    (bitblt 64 32 src 0 0 sys.int::*bochs-framebuffer* -16 500)
  -    (bitblt 64 32 src 0 0 sys.int::*bochs-framebuffer* 500 -16)
  -    (bitblt 64 32 src 0 0 sys.int::*bochs-framebuffer* 300 1000)
  -    (bitblt 64 32 src 0 0 sys.int::*bochs-framebuffer* 750 300)
  -    (bitblt 128 64 src 0 0 sys.int::*bochs-framebuffer* 600 600)
  -    (bitblt -64 -32 src 0 0 sys.int::*bochs-framebuffer* 700 700)
  -    (bitblt 64 32 src 20 10 sys.int::*bochs-framebuffer* 400 400)))
   
   (defun %simple-array-data-pointer (array)
     "Find the address of ARRAY's first data element."
  
positive.code:   (sys.lap-x86:mov32 (:rdi) :eax) ; rdx = pixel (XRGB)
    out
    (sys.lap-x86:ret)
    ;(:align 4) ; 16 byte alignment for XMM. (TODO)
    alpha-shuffle
    (:d64/le #x0000000000010101)
  
negative.code:   (sys.lap-x86:mov32 :ecx :eax) ; ecx = pixel (ARGB)
    (sys.lap-x86:and32 :ecx #xFF000000) ; ecx = pixel-alpha (A000)
    (sys.lap-x86:jz out) ; Fully transparent, bail out.
    ;; Read destination.
    (sys.lap-x86:mov32 :edx (:rdi)) ; rdx = pixel (XRGB)
    ;; Check for fully opaque source.
    (sys.lap-x86:cmp32 :ecx #xFF000000)
    (sys.lap-x86:je fully-opaque)
    ;; MMX pixel blend.
    ;; RAX = Source pixel.
    ;; RCX = Alpha channel of source pixel at (byte 8 24).
  