By changing the font style of the window, you also change the font style of any newly created child controls.
Window.fontsize
Get or set the window font size, a number that represent the font size in pixels.
Example
--! luart-extensions
import ui
-- create a simple window
local win = ui.Window("Window.fontsize sample", 640, 200)
win.fontsize = 16
local label = ui.Label(win, "Hello World in '"..win.font.."' font, "..win.fontsize.."px")
win:show()
-- update the user interface until the user closes the window
repeat
ui.update()
until not win.visible