PICARD-2088: Override QSettings config file syncing

As the default implementation for synchronizing the config file can lead to application freezes override it.
Ensure the config file is not updated by more than one process by locking the file using fasteners.

picard/config.py

@@ -32,6 +32,8 @@ import os
 import shutil
 import threading
 
+import fasteners
+
 from PyQt5 import QtCore
 
 from picard import (
@@ -129,6 +131,7 @@ class Config(QtCore.QSettings):
         """Common initializer method for :meth:`from_app` and
         :meth:`from_file`."""
 
+        self.setAtomicSyncRequired(False)
         self.application = ConfigSection(self, "application")
         self.setting = ConfigSection(self, "setting")
         self.persist = ConfigSection(self, "persist")
@@ -139,6 +142,18 @@ class Config(QtCore.QSettings):
         self._version = Version.from_string(self.application["version"])
         self._upgrade_hooks = dict()
 
+    def event(self, event):
+        if event.type() == QtCore.QEvent.UpdateRequest:
+            log.debug('Config file update requested on thread %r', threading.get_ident())
+            self.sync()
+            return True
+        else:
+            return super().event(event)
+
+    def sync(self):
+        with fasteners.InterProcessLock(self.fileName()):
+            super().sync()
+
     @classmethod
     def from_app(cls, parent):
         """Build a Config object using the default configuration file

requirements-macos-10.12.txt

@@ -1,5 +1,6 @@
 python-dateutil==2.8.1
 discid==1.2.0
+fasteners==0.16
 markdown==3.2.2
 mutagen==1.45.1
 pyobjc-core==6.2.2

requirements-macos-10.14.txt

@@ -1,5 +1,6 @@
 python-dateutil==2.8.1
 discid==1.2.0
+fasteners==0.16
 markdown==3.2.2
 mutagen==1.45.1
 pyobjc-core==6.2.2

requirements-win.txt

@@ -1,5 +1,6 @@
 python-dateutil==2.8.1
 discid==1.2.0
+fasteners==0.16
 markdown==3.2.2
 mutagen==1.45.1
 PyQt5==5.15.2

requirements.txt

@@ -1,5 +1,6 @@
 python-dateutil>=2.7.3
 discid
+fasteners
 markdown
 mutagen>=1.37
 pyobjc-core<7.0; sys_platform == 'darwin'