# File rbSnack/tkSnackUtil.rb, line 385
   def initialize canvas
     @canvas     = canvas
     @constraint = nil
     @selIndex   = nil #for horizontal line selection
     @boxes,  @vLine, @hLine, @bkDot=[], [], [], []
     @canvas.bind("1", proc{ |e| do_press(e.x, e.y)})
     @canvas.bind("B1-Motion", proc{ |x,y| do_move(x, y)},"%x %y")
     @canvas.bind("ButtonRelease-1",proc{ |x,y| do_release(x, y)},"%x %y")
   end