QSystemTrayIcon size not respected when run from system terminal but not vscode

Question

I have the following simple Qt app that creates a system tray icon from a given text. When I run the app via vscode terminal, everything seems to be fine (see the screenshot below):

Strangely, when I run the app via system terminal (bash), icon size is not respected, and the text is shrunk (see below):

I'd appreciate it if anyone could shed some light what might be causing this strange behaviour. Here's the code:

import sys
from PyQt5.QtWidgets import *
from PyQt5 import QtCore, QtWidgets, QtGui, QtSvg


def create_tray_icon(label):
    r"""Creates QIcon with the given label."""
    w, h = 22*4, 22
    pixmap = QtGui.QPixmap(w, h)
    pixmap.fill(QtCore.Qt.transparent)  # alternative: QtGui.QColor("white")
    painter = QtGui.QPainter(pixmap)
    painter.setPen(QtGui.QColor("white"))
    align = int(QtCore.Qt.AlignRight | QtCore.Qt.AlignVCenter)
    painter.drawText(pixmap.rect(), align, str(label))
    painter.end()
    icon = QtGui.QIcon()
    icon.addPixmap(pixmap)
    return icon


class SystemTrayIcon(QtWidgets.QSystemTrayIcon):

    def __init__(self, icon, parent=None):
        QtWidgets.QSystemTrayIcon.__init__(self, icon, parent)
        self.menu = QtWidgets.QMenu(parent)
        exitAction = self.menu.addAction("Exit")
        exitAction.triggered.connect(lambda: sys.exit())
        self.setContextMenu(self.menu)


def memprofilerApp():
    r"""Runs the Qt Application."""
    QApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
    QApplication.setAttribute(QtCore.Qt.AA_UseHighDpiPixmaps)
    app = QApplication(sys.argv)
    icon = create_tray_icon(label="Hello world!")
    trayIcon = SystemTrayIcon(icon)
    trayIcon.show()
    sys.exit(app.exec_())


if __name__ == '__main__':
    memprofilerApp()

Answer 1

After inspecting environment variables (by running env) on vscode terminal and comparing it with that on system terminal, it turned out that the culprit was XDG_CURRENT_DESKTOP! In vscode terminal (which QIcon size is respected), it is set to UNITY, whereas in system terminal it is set to ubuntu:GNOME.

I don't know the root cause, but a quick fix is to use the following script to run the app:

#!/bin/bash
XDG_CURRENT_DESKTOP=Unity
/path/to/python main.py

Just out of curiosity, if anyone knows why ubuntu:GNOME cause the QIcon sizing to break, please let us know!