Screen occasionally goes black on image swap

[BillMerryman]

I have a simple application that updates a screen (Adafruit 1.14" 240x135 Color TFT Display + MicroSD Card Breakout - ST7789 Product ID: 4383) from a Pi Zero W 2, every 1/2 to 1 second, rendering moving 'eyes'. It consists of a main program (face_test.py) and a threaded class (face.py). The updating is done from a thread. The eyes are transparent PNG files that are enumerated from a text file and loaded at startup. In the thread, the code creates a green background, pastes the 'eyes' onto it, and then displays the image to the screen. This part appears to work fine. The main program can call a method on the class that tells it which PNG it should be using. At random times, this part appears to be resetting the screen, as it goes black and doesn't display anything else for the remainder of the run. I've attached all files, with the Python files as txt files.

The main program:

import os
import time

import face

def main():
    face_animate = face.FaceAnimate()
    face_animate.start()
    for x in range(100):
        time.sleep(2)
        face_animate.set_face("squint")
        time.sleep(2)   
        face_animate.set_face("regular")
    face_animate.stop()
    face_animate.join()

if __name__ == "__main__":
    main()

The threaded class:

import os
import threading
import random
import time
import digitalio
import board
from PIL import Image, ImageDraw
from adafruit_rgb_display import st7789

# Configuration for CS and DC pins (these are PiTFT defaults):
cs_pin = digitalio.DigitalInOut(board.CE0)
dc_pin = digitalio.DigitalInOut(board.D25)
reset_pin = digitalio.DigitalInOut(board.D24)

# Config for display baudrate (default max is 24mhz):
BAUDRATE = 24000000

# Setup SPI bus using hardware SPI:
spi = board.SPI()

disp = st7789.ST7789(spi, 
        rotation=270, 
        width=135, 
        height=240, 
        x_offset=53, 
    y_offset=40, # 1.14" ST7789
    cs=cs_pin,
    dc=dc_pin,
    rst=reset_pin,
    baudrate=BAUDRATE,
    )

if disp.rotation % 180 == 90:
    height = disp.width  # we swap height/width to rotate it to landscape!
    width = disp.height
else:
    width = disp.width  # we swap height/width to rotate it to landscape!
    height = disp.height

class FaceAnimate(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)
        self.face_offset_x = 0
        self.face_offset_y = 0
        self.images = {}
        self.load_images(os.getcwd() + "/images.txt")
        self.face_key = list(self.images.keys())[0]
        self.face = self.images[self.face_key]      
        self.running = True
        random.seed()

    def load_images(self, file_list_path):
        try:
            with open(file_list_path, 'r') as file:
                for line in file:
                    image_filename = line.strip()
                    key = image_filename.split('.')[0]
                    image = Image.open(os.getcwd() + "/" + image_filename)
                    self.images[key] = image
        except Exception as e:
            print(f"{e}")

    def run(self):
        while self.running:
            time.sleep(random.uniform(.5, 1))
            self.face_offset_x = random.randint(-5, 5)
            self.face_offset_y = random.randint(-5, 5)
            self.show_face()

    def set_face(self, face_name):
        self.face = self.images[face_name]
        self.show_face()

    def get_background(self, R, G, B):
        image = Image.new("RGB", (width, height))
        draw = ImageDraw.Draw(image)
        draw.rectangle((0, 0, width, height), outline=0, fill=(R, G, B))
        return image

    def show_face(self):
        background = self.get_background(int("6B", 16), int("8E", 16), int("23",16))
        background.paste(self.face, (self.face_offset_x, self.face_offset_y), self.face)
        disp.image(background)

    def stop(self):
        self.running = False

face.txt images.txt face_test.txt

[BillMerryman]

Okay, guess I rubber-duck debugged. I implemented a lock and acquired the lock before each call to 'show_face' and that appears to have resolved it. Is ST7789 not thread-safe? Or is it just the ST7789.image method that isn't thread safe?

[BillMerryman]

Yep, deleted the 'with self.lock:' statements from everywhere and added it just in the line before setting the image:

        with self.lock:     
            disp.image(background)

Problem remains resolved.