By changing the font style of the Panel, you also change the font style of any newly created child controls.
Panel.fontsize
Get or set the Panel font size, a number that represent the font size in pixels.
Example
--! luart-extensions
import ui
-- create a fixed Panel
local win = ui.Window("Panel.fontsize sample", "fixed", 320, 200)
-- create a Panel
local panel = ui.Panel(win, 0, 0, 100, 100)
panel.bgcolor = 0x00a060
panel:center()
-- change its font
panel.font = "Segoe Print"
panel.fontsize = 12
-- add a child Label
ui.Label(panel, "Label"):center()
await win:showasync()