code exch ( >a >b --- )
  sp )+  a0  long move
  sp )+  a1  long move
  a0 )  d0  long move
  a1 )  d1  long move
  d0  a1 )  long move
  d1  a0 )  long move
c;


\ ========================================================================


variable color
variable dx
variable dy
variable incr1
variable incr2
variable d
variable x
variable y
variable flag
variable x0
variable y0
variable x1
variable y1
variable x2
variable y2

variable xxx
variable yyy

variable xdir
variable ydir
variable >xsel
variable >ysel

: fline ( x1 y1 x2 y2 --- )
  y2 ! x2 ! y1 ! x1 !
  flag off
  
  x2 @ x1 @ -		\ x2-x1
  dup x0 !
  dup 0> if 1 else -1 then xdir !
  abs
  dup dx !		\ dx


  y2 @ y1 @ -		\ dx y2-y1
  dup y0 !
  dup 0> if 1 else -1 then ydir !
  abs
  dup dy !		\ dx dy

  x1 @ y1 @ color @ plot

  < if			\
    x2 y2 exch  dx dy exch  x1 y1 exch  x0 y0 exch  xdir ydir exch
    flag on
  then

  dy @ 2*		\ dy<<1
  dup dx @ - d !
  incr1 !		\
  dy @ dx @ - 2* incr2 !

\  x0 @ 0> if 1 else -1 then xdir !
\  y0 @ 0> if 1 else -1 then ydir !

  begin
    x1 @ x2 @ - while

    xdir @ x1 +!
    d @ 0< if
      incr1
    else
      ydir @ y1 +!
      incr2
    then
    @ d +!

    x1 @ y1 @ 
    flag @ if swap then
    color @ plot

  repeat
;


\ ========================================================================


defer line
' fline is line

: foo [ hex ] 100 rnd 100 rnd 100 rnd 100 rnd  100 rnd color ! line ;
: bar 0 do foo loop ; 


get_fb
\ fb _fb !

.( Done.) cr