* `App.screen.print(text, x,y)` -- print the given `text` in the current font
  using the current color so its top-left corner is at the specified
  coordinates of the app window.

* `App.screen.print(text, x,y)` -- print the given string `text` in the
  current font using the current color so its top-left corner is at the
  specified coordinates of the app window.

* `App.screen.draw(text, x,y)` -- print the given Text object `text` in the
  current font using the current color so its top-left corner is at the
  specified coordinates of the app window.
  (Based on [LÖVE](https://love2d.org/wiki/love.graphics.draw) albeit with
  restrictions; this is only for Text objects.)

  App.screen.draw = love.graphics.draw

end
function App.screen.draw(obj, x,y)
  if type(obj) == 'userdata' then
    -- ignore most things as graphics the test harness can't handle
  elseif obj.type == 'text' then
    App.screen.print(obj.data, x,y)
  else
    print(obj.type)
    assert(false)
  end