USING: arrays kernel math sequences
accessors ui ui.gadgets ui.gadgets.canvas ui.render math.order math.rectangles math.vectors opengl opengl.gl namespaces ;
IN: dragon

: zig ( p1 p2 -- p1 pI p2 )
    [ [ first2 ] bi@
      [ [ rot swap + swap ] dip - + 2 / ] 4keep
      [ rot + swap ] dip + + 2 / 2array
    ] 2keep [ swap ] dip ;

: zag ( p1 p2 -- p1 pA p2 )
    [ [ first2 ] bi@
      [ [ rot swap + swap ] dip + - 2 / ] 4keep
      [ rot swap - swap ] dip + + 2 / 2array
    ] 2keep [ swap ] dip ;

: dragon' ( p1 p2 p3 d -- seq )
    dup zero? [
        2drop 2array
    ] [
        1 - swap dupd swap [ dupd swap ] 2dip ! p1 p2 d p2 p3 d
        [ zig ] 4dip [ zag ] dip ! p1 pI p2 d p2 pA p3 d
        [ dragon' ] 4dip dragon' ! p1 pI p2 d dragon' / p2 pA p3 d dragon'
        append
    ] if ;

: dragon ( -- seq ) ! [ math.vectors:normalize ] map
    100 200 [ dup 2array ] bi@ zig 2 dragon' ; ! prettyprint:.
! GL_LINE_STRIP glBegin dragon [ glVertex2dv ] each glEnd

: draw-dragon ( -- )
    8 2 - glLineWidth
    8 2 - glPointSize
    1.0 1.0 1.0 1.0 glColor4d
    GL_LINE_STRIP glBegin
    dragon [ normalize ] map [ glVertex2dv ] each
    glEnd ;

TUPLE: dragon-canvas < canvas ;

M: dragon-canvas layout* delete-canvas-dlist ;

M: dragon-canvas draw-gadget* [ draw-dragon ] draw-canvas ;

M: dragon-canvas pref-dim* drop { 400 400 } ;

MAIN-WINDOW: dragon-window { { title "Dragon Curve" } }
  dragon-canvas new-canvas >>gadgets ;

MAIN: dragon-window