Fix QDesktopServices.openUrl() for AppImage on Linux

cura/OAuth2/AuthorizationService.py

@@ -3,6 +3,7 @@
 
 import json
 from datetime import datetime, timedelta
+import os
 from typing import Optional, TYPE_CHECKING
 from urllib.parse import urlencode
 
@@ -13,6 +14,7 @@ from PyQt5.QtGui import QDesktopServices
 
 from UM.Logger import Logger
 from UM.Message import Message
+from UM.Platform import Platform
 from UM.Signal import Signal
 
 from cura.OAuth2.LocalAuthorizationServer import LocalAuthorizationServer
@@ -164,9 +166,24 @@ class AuthorizationService:
             "code_challenge_method": "S512"
         })
 
+        # GITHUB issue #6194: https://github.com/Ultimaker/Cura/issues/6194
+        # With AppImage 2 on Linux, the current working directory will be somewhere in /tmp/<rand>/usr, which is owned
+        # by root. For some reason, QDesktopServices.openUrl() requires to have a usable current working directory,
+        # otherwise it doesn't work. This is a workaround on Linux that before we call QDesktopServices.openUrl(), we
+        # switch to a directory where the user has the ownership.
+        old_work_dir = ""
+        if Platform.isLinux():
+            # Change the working directory to user home
+            old_work_dir = os.getcwd()
+            os.chdir(os.path.expanduser("~"))
+
         # Open the authorization page in a new browser window.
         QDesktopServices.openUrl(QUrl("{}?{}".format(self._auth_url, query_string)))
 
+        if Platform.isLinux():
+            # Change the working directory back
+            os.chdir(old_work_dir)
+
         # Start a local web server to receive the callback URL on.
         self._server.start(verification_code)