require 'tk'

c = TkCanvas.new.pack
c.bind( '1', proc{|x, y| $id = create_box(c, x, y) }, "%x %y")
c.bind( 'B1-Motion', proc{|x, y| adjust_box( c, x, y ) }, "%x %y" )

$x0, $y0 = 0, 0
def create_box(c, x, y)
  box = TkcRectangle.new(c, x, y, x, y, 'width'=>2)
  c.dtag 'selected'
  c.addtag_withtag 'selected', box.id
  $x0, $y0 = x, y
end
def adjust_box( c, x, y )
  c.coords('selected', $x0, $y0, x, y )
end

Tk.mainloop