Merge pull request #156 from janvolck/main

relax displayio._background thread

diff --combined displayio/__init__.py
index 9e9d97741db91c70320b3e397067f503347aaee3,b22ce94c9113c19861d21f5afcbe4ff4d63c577c..e42d24a60d48c00019de9cd474d0a8f458497f96
--- 1/displayio/__init__.py
--- 2/displayio/__init__.py
+++ b/displayio/__init__.py
@@@ -17,8 -17,14 +17,9 @@@ displayio for Blink
  
  """
  import threading
+ import time
  from typing import Union
  
 -import fourwire
 -import i2cdisplaybus
 -from busdisplay import BusDisplay
 -from busdisplay._displaybus import _DisplayBus
 -from epaperdisplay import EPaperDisplay
  from ._bitmap import Bitmap
  from ._colorspace import Colorspace
  from ._colorconverter import ColorConverter
@@@ -28,6 -34,11 +29,6 @@@ from ._palette import Palett
  from ._tilegrid import TileGrid
  from ._constants import CIRCUITPY_DISPLAY_LIMIT
  
 -# 8.x Backwards compatibility, remove at 10.x or
 -# when compatibility is removed from core displayio
 -Display = BusDisplay
 -FourWire = fourwire.FourWire
 -I2CDisplay = i2cdisplaybus.I2CDisplayBus
  
  __version__ = "0.0.0+auto.0"
  __repo__ = "https://github.com/adafruit/Adafruit_Blinka_displayio.git"
@@@ -37,12 -48,16 +38,16 @@@ displays = [
  display_buses = []
  
  
- def _background():
+ def _background(stop_event):
      """Main thread function to loop through all displays and update them"""
-     while True:
+     while not stop_event.is_set():
          for display in displays:
              display._background()  # pylint: disable=protected-access
  
+         # relax system when _background does nothing
+         # and we are in a while True loop consuming lots of CPU
+         time.sleep(0.0)
+ 
  
  def release_displays() -> None:
      """Releases any actively used displays so their busses and pins can be used again.
@@@ -59,16 -74,14 +64,16 @@@
      display_buses.clear()
  
  
 -def allocate_display(new_display: Union[BusDisplay, EPaperDisplay]) -> None:
 +def allocate_display(
 +    new_display: Union["busdisplay.BusDisplay", "epaperdisplay.EPaperDisplay"]
 +) -> None:
      """Add a display to the displays pool and return the new display"""
      if len(displays) >= CIRCUITPY_DISPLAY_LIMIT:
          raise RuntimeError("Too many displays")
      displays.append(new_display)
  
  
 -def allocate_display_bus(new_display_bus: _DisplayBus) -> None:
 +def allocate_display_bus(new_display_bus: "busdisplay._displaybus._DisplayBus") -> None:
      """Add a display bus to the display_buses pool and return the new display bus"""
      if len(display_buses) >= CIRCUITPY_DISPLAY_LIMIT:
          raise RuntimeError(
@@@ -77,7 -90,10 +82,10 @@@
      display_buses.append(new_display_bus)
  
  
- background_thread = threading.Thread(target=_background, daemon=True)
+ background_thread_stop_event = threading.Event()
+ background_thread = threading.Thread(
+     target=_background, args=(background_thread_stop_event,), daemon=True
+ )
  
  
  # Start the background thread
@@@ -88,6 -104,7 +96,7 @@@ def _start_background()
  
  def _stop_background():
      if background_thread.is_alive():
+         background_thread_stop_event.set()
          # Stop the thread
          background_thread.join()