Tinkering with CircuitPython and displayio

code.py

import time

from rtc import set_time_source
from board import SPI, RX, TX, D9, D10

from busio import UART
from displayio import FourWire, Group, release_displays

from adafruit_gps import GPS
from adafruit_ili9341 import ILI9341
from adafruit_display_text.label import Label

from font_loader import FontLoader
from window import Window
from watcher import Watcher

spi = SPI()
tft_cs = D9
tft_dc = D10

release_displays()

bus = FourWire(spi, command=tft_dc, chip_select=tft_cs)
display = ILI9341(bus, width=240, height=320, rotation=270)

UI = Group(max_size=1)
window = Window(UI, title='GPS', width=240, height=320)

datetime = Label(FontLoader().small_font, max_glyphs=16, color=0xFFFFFF, x=2)
latitude = Label(FontLoader().small_font, max_glyphs=20, color=0xFFFFFF, x=2, y=12, text='Waiting for fix...')
longitude = Label(FontLoader().small_font, max_glyphs=20, color=0xFFFFFF, x=2, y=32)
satellites = Label(FontLoader().small_font, max_glyphs=15, color=0xFFFFFF, x=2, y=52)

content = window.get_content_pane(4)
content.append(datetime)
content.append(latitude)
content.append(longitude)
content.append(satellites)

datetime.y = content.height - 12

display.show(UI)
display.refresh_soon()
display.wait_for_frame()

uart = UART(TX, RX, baudrate=9600, timeout=3)
gps = GPS(uart, debug=False)

set_time_source(gps)

def update(action):
  def update_action():
    if not gps.has_fix:
      return

    action()

    display.refresh_soon()
    display.wait_for_frame()

  return update_action

def update_latitude():
  latitude.text = 'Latitude: {:.4f}'.format(gps.latitude)

def update_longitude():
  longitude.text = 'Longitude: {:.4f}'.format(gps.longitude)

def update_satellites():
  satellites.text = 'Satellites: {}'.format(gps.satellites)

def update_datetime():
  datetime.text = '{:02}/{:02}/{:04} {:02}:{:02}'.format(
    gps.timestamp_utc.tm_mon,
    gps.timestamp_utc.tm_mday,
    gps.timestamp_utc.tm_year,
    gps.timestamp_utc.tm_hour,
    gps.timestamp_utc.tm_min
  )
  datetime.x = (content.width - datetime.bounding_box[2]) // 2

latitude_watcher = Watcher(lambda: gps.latitude, action=update(update_latitude))
longitude_watcher = Watcher(lambda: gps.longitude, action=update(update_longitude))
satellites_watcher = Watcher(lambda: gps.satellites, action=update(update_satellites))
datetime_watcher = Watcher(lambda: gps.timestamp_utc.tm_min, action=update(update_datetime))

gps.send_command(b'PMTK220,5000')
gps.send_command(b'PMTK300,1000,0,0,0,0')
gps.send_command(b'PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0')

while True:
  gps.update()
  latitude_watcher.update()
  longitude_watcher.update()
  satellites_watcher.update()
  datetime_watcher.update()

font_loader.py

from adafruit_bitmap_font import bitmap_font

cwd = ("/"+__file__).rsplit('/', 1)[0]

small_font = cwd + "/fonts/Arial-16.bdf"

class FontLoader:
  class __FontLoader:
    def __init__(self):
      self.small_font = bitmap_font.load_font(small_font)

      glyphs = b'0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-,.: '

      self.small_font.load_glyphs(glyphs)

  __instance = None

  def __init__(self):
    if not FontLoader.__instance:
      FontLoader.__instance = FontLoader.__FontLoader()

  def __getattr__(self, name):
    return getattr(FontLoader.__instance, name)

watcher.py

class Watcher:
  def __init__(self, current, *, action=None):
    self.last = None
    self.current = current
    self.action = action

  def update(self):
    try:
      value = self.current()

      if value != self.last:
        self.last = value

        self.action()
    except:
      print("Unexpected error")

window.py

from displayio import Group

from adafruit_display_text.label import Label
from adafruit_display_shapes.roundrect import RoundRect

from font import Font

class Window(Group):
  def __init__(self, parent, *, title=None, width=None, height=None):
    super().__init__(max_size=3)

    if not width or not height:
      raise RuntimeError("Please provide a width and height")

    self.width = width
    self.height = height

    parent.append(self)

    self._content = None
    self._main = Group(max_size=1)
    self.append(self._main)

    self._main.append(
      RoundRect(0, 0, self.width, self.height, 3, fill=0x330033, outline=0xFF00FF)
    )

    if title:
      self._titlebar = Group(max_size=2)
      self.append(self._titlebar)

      self._titlebar.append(
        RoundRect(0, 0, self.width, 30, 3, fill=0x550055, outline=0xFF00FF)
      )
      self._titlebar.append(
        Label(Font().small_font, text=title, color=0xFFFF00, x=8, y=14)
      )
    else:
      self._titlebar = None

  def get_content_pane(self, max_size=1):
    if not self._content:
      y = 32 if self._titlebar else 2
      width = self.width - 4
      height = self.height - (34 if self._titlebar else 4)

      self._content = Content(self, max_size=max_size, x=2, y=y, width=width, height=height)

    return self._content

class Content(Group):
  def __init__(self, parent, *, width=None, height=None, **kwargs):
    super().__init__(**kwargs)

    if not width or not height:
      raise RuntimeError("Please provide a width and height")

    self.width = width
    self.height = height

    parent.append(self)