Using PyQT6 on Debian 13 and about 50% of the time, when I run by script, I get no window drawn?

[Jibun-no-Kage]

Using PyQT6 on Debian 13 and about 50% of the time, when I run by script, I get no window drawn? An application icon appears on the dash/dock (using GNOME), and the icon menu works, I can close the application from there, but again no window ever appears. This happens completely randomly. I can close the application wait a second or two and it will work, repeat the sequence and it will not work. Must confusing. Below is the code, it is pretty simple, or so I think.

LED Module...

import sys
from PyQt6.QtWidgets import QWidget, QVBoxLayout, QLabel, QApplication, QPushButton, QHBoxLayout, QFrame
from PyQt6.QtGui import QPainter, QColor, QPen
from PyQt6.QtCore import Qt, QSize

class LEDWidget(QFrame):
    """
    A custom QFrame widget to display a square LED with a label.
    """
    def __init__(self, label_text, parent=None):
        super().__init__(parent)
        self.setFixedSize(100, 80) # Fixed size for the whole widget
        self.setFrameShape(QFrame.Shape.StyledPanel)
        self.setLineWidth(1)

        layout = QVBoxLayout()
        layout.setAlignment(Qt.AlignmentFlag.AlignCenter)

        # Custom LED indicator area (a QWidget that will be custom drawn)
        self._led = QWidget(self)
        self._led.setFixedSize(40, 40)
        # Set a styled background for the LED itself, including a border
        self._led.setStyleSheet("""
            QWidget {
                border: 2px solid black;
                border-radius: 5px; /* Optional: for slightly rounded corners */
            }
        """)

        # Label for the LED
        self._label = QLabel(label_text, self)
        self._label.setAlignment(Qt.AlignmentFlag.AlignCenter)

        layout.addWidget(self._led, alignment=Qt.AlignmentFlag.AlignCenter)
        layout.addWidget(self._label, alignment=Qt.AlignmentFlag.AlignCenter)
        self.setLayout(layout)

        self._is_on = False
        self._update_led_color()

    def is_on(self):
        return self._is_on

    def set_on(self, state):
        self._is_on = state
        self._update_led_color()

    def toggle(self):
        self._is_on = not self._is_on
        self._update_led_color()

    def _update_led_color(self):
        # Update the background color using stylesheets
        color = "gray" if (self._is_on is None) else ("green" if self._is_on else "red")
        self._led.setStyleSheet(f"""
            QWidget {{
                border: 2px solid black;
                border-radius: 5px;
                background-color: {color};
            }}
        """)

Main...

mport sys
from PyQt6.QtWidgets import QApplication, QMainWindow, QWidget, QVBoxLayout, QHBoxLayout, QPushButton
from PyQt6.QtCore import QSize
from led_widget import LEDWidget

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("On Air Monitor")
        self.setGeometry(0, 0, 100, 250)

        central_widget = QWidget()
        main_layout = QVBoxLayout()

        # Layout for LEDs
        leds_layout = QHBoxLayout()
        self.led1 = LEDWidget("Booth")
        self.led2 = LEDWidget("Production")
        self.led3 = LEDWidget("Signs")
        self.led4 = LEDWidget("Alive")
        self.led5 = LEDWidget("Stream")
        self.led6 = LEDWidget("Switcher")

        leds_layout.addWidget(self.led1)
        leds_layout.addWidget(self.led2)
        leds_layout.addWidget(self.led3)
        leds_layout.addWidget(self.led4)
        leds_layout.addWidget(self.led5)
        leds_layout.addWidget(self.led6)

        self.led1.set_on(None)
        self.led2.set_on(None)
        self.led3.set_on(None)
        self.led4.set_on(None)
        self.led5.set_on(None)
        self.led6.set_on(None)

        # Layout for buttons
        buttons_layout = QHBoxLayout()
        #self.toggle_button = QPushButton("Toggle All LEDs")
        #self.toggle_button.clicked.connect(self.toggle_all_leds)

        self.close_button = QPushButton("OK")
        self.close_button.setFixedSize(QSize(100,30))
        self.close_button.clicked.connect(self.close)

        #buttons_layout.addWidget(self.toggle_button)
        buttons_layout.addWidget(self.close_button)

        main_layout.addLayout(leds_layout)
        main_layout.addLayout(buttons_layout)
        central_widget.setLayout(main_layout)
        self.setCentralWidget(central_widget)

    #def toggle_all_leds(self):
        # Example of how to turn LEDs on and off
        #if self.led1.is_on():
            #self.led1.set_on(False)
            #self.led2.set_on(False)
            #self.led3.set_on(False)
        #else:
            #self.led1.set_on(True)
            #self.led2.set_on(True)
            #self.led3.set_on(True)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec())

The Qt environment does throw a few warnings... but none of these seem to be material, since they are consistently presented both when the window appears and fails to appear.

# /root/Test/bin/python3 Test4.py
Failed to create wl_display (No such file or directory)
qt.qpa.plugin: Could not load the Qt platform plugin "wayland" in "" even though it was found.
qt.qpa.theme.dbus: Session DBus not running.
qt.qpa.theme.dbus: Application will not react to setting changes.
 Check your DBus installation.
qt.qpa.theme.gnome: dbus connection failed. Last error:  QDBusError("org.freedesktop.DBus.Error.NoReply", "Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.")
qt.qpa.theme.dbus: Session DBus not running.
qt.qpa.theme.dbus: Application will not react to setting changes.
 Check your DBus installation.
qt.qpa.theme.gnome: dbus connection failed. Last error:  QDBusError("org.freedesktop.DBus.Error.NoReply", "Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.")

When window fails to appear...

# /root/Test/bin/python3 Test4.py
Failed to create wl_display (No such file or directory)
qt.qpa.plugin: Could not load the Qt platform plugin "wayland" in "" even though it was found.
qt.qpa.theme.dbus: Session DBus not running.
qt.qpa.theme.dbus: Application will not react to setting changes.
 Check your DBus installation.
qt.qpa.theme.gnome: dbus connection failed. Last error:  QDBusError("org.freedesktop.DBus.Error.NoReply", "Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.")
qt.qpa.theme.dbus: Session DBus not running.
qt.qpa.theme.dbus: Application will not react to setting changes.
 Check your DBus installation.
qt.qpa.theme.gnome: dbus connection failed. Last error:  QDBusError("org.freedesktop.DBus.Error.NoReply", "Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.")

Any help appreciated! Any more details required?

[jsulm]

@Jibun-no-Kage Do you use Wayland?

[IgKh]

@Jibun-no-Kage why are you running the application as root?