Fullscreen GUI app from Docker container on Coral Dev Board

Question

I'm trying to run a Python GUI app from a docker container, but when I'm trying to display on fullscreen, nothing shows up. If I'm not calling cv2.setWindowProperty("frame", cv2.WND_PROP_FULLSCREEN, cv2.WINDOW_FULLSCREEN), the windows appears on screen normaly.

This is the Dockerfile used :

# syntax = docker/dockerfile:1.0-experimental

FROM arm64v8/debian:latest

RUN apt update && apt install -y \
  ca-certificates \
  gnupg \
  curl

RUN echo "deb https://packages.cloud.google.com/apt coral-edgetpu-stable main" \
  | tee /etc/apt/sources.list.d/coral-edgetpu.list \
  && curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -

RUN apt update && apt install -y \
  python3 \
  python3-pip \
  python3-opencv \
  python3-pycoral \
  zlib1g-dev \
  libjpeg-dev

RUN pip3 install \
  v4l2 \
  screeninfo \
  pillo

And this is the script:

import cv2
import screeninfo

# Capture video from webcam
vid_capture = cv2.VideoCapture(1)

while True:
    # Capture each frame of webcam video
    screen = screeninfo.get_monitors()[0]
    cv2.namedWindow("frame", cv2.WND_PROP_FULLSCREEN)
    cv2.moveWindow("frame", screen.x - 1, screen.y - 1)
    cv2.setWindowProperty("frame", cv2.WND_PROP_FULLSCREEN, cv2.WINDOW_FULLSCREEN)
    ret, frame = vid_capture.read()
    cv2.imshow("frame", frame)
    # Close and break the loop after pressing "x" key
    if cv2.waitKey(1) & 0xFF == ord("x"):
        break

# close the already opened camera
vid_capture.release()
# close the window and de-allocate any associated memory usage
cv2.destroyAllWindows()

I'm using the following docker run command:

docker run -d --rm \
  --device /dev/apex_0:/dev/apex_0 \
  --device /dev/video1:/dev/video1 \
  -e DISPLAY=$DISPLAY \
  -v /tmp/.X11-unix/:/tmp/.X11-unix \
  guiapp bash

Before running the container, I'm making sure that the environment is configured with these:

export DISPLAY=:0
xhost +

I can't think of anything that may cause this strange behaviour.

EDIT: after further investigation, I found out that I face the same problem when logged in as root.