require 'fltk'

class Board < FLTK::Widget
  def initialize(w,h)
    size(w,h)
    @row = 0
    @col = 0
  end

  # x, y, w and h are local variables, since those are declared in this method.
  # You should not confuse Widget's method such as w() with local variable w. :)
  def resize(x, y, w, h)
    @unit = w/8
    w = 8*@unit
    h = 8*@unit
    super(x,y,w,h)
  end
  
  def draw()
    super()
    drawGrid
    drawPiece(@row,@col, FLTK::BLACK)
  end
  
  def handle(code)
    if(code == FLTK::ENTER)
      return true
    end
    if(code == FLTK::MOVE)
      @row = FLTK::event_y / @unit
      @col = FLTK::event_x / @unit
      redraw()
    end
    return super(code)
  end
  
  def drawGrid
    FLTK::color(FLTK::BLUE)
    FLTK::rectf(x,y,w,h)
    FLTK::color(FLTK::WHITE)
    0.step(w, @unit) do | col | FLTK::line(x+col, y, x+col, y+h) end
    0.step(h, @unit) do | row | FLTK::line(x, y+row, x+w, y+row) end
  end
  
  def drawPiece(row,col, color)
    FLTK::color(color)
    thisX = col*@unit
    thisY = row*@unit
    FLTK::pie(thisX, thisY, @unit, @unit,0,360)
  end
end

class MyWindow < FLTK::DoubleWindow
  def initialize
    super(300, 300, 'Drawing'){|win|
      b = Board.new(w,h)
      resizable(self)
      yield(win)
    }
  end
end

MyWindow.new{|win|
  win.show()
}
FLTK::run()