Backup/restore for preferences stored in metadata.db

src/calibre/gui2/ui.py

@@ -738,6 +738,7 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin, # {{{
             # Goes here, because if cf is valid, db is valid.
             db.prefs['field_metadata'] = db.field_metadata.all_metadata()
             db.commit_dirty_cache()
+            db.prefs.write_serialized(prefs['library_path'])
         for action in self.iactions.values():
             if not action.shutting_down():
                 return

src/calibre/library/prefs.py

@@ -5,7 +5,7 @@ __license__   = 'GPL v3'
 __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import json
+import json, os
 
 from calibre.constants import preferred_encoding
 from calibre.utils.config import to_json, from_json
@@ -71,3 +71,30 @@ class DBPrefs(dict):
         key = u'namespaced:%s:%s'%(namespace, key)
         self[key] = val
 
+    def write_serialized(self, library_path):
+        try:
+            to_filename = os.path.join(library_path, 'metadata_db_prefs_backup.json')
+            with open(to_filename, "wb") as f:
+                f.write(json.dumps(self, indent=2, default=to_json))
+        except:
+            import traceback
+            traceback.print_exc()
+
+    def read_serialized(self, library_path):
+        try:
+            from_filename = os.path.join(library_path,
+                    'metadata_db_prefs_backup.json')
+            with open(from_filename, "rb") as f:
+                self.clear()
+                d = json.load(f, object_hook=from_json)
+                self.db.conn.execute('DELETE FROM preferences')
+                for k,v in d.iteritems():
+                    raw = self.to_raw(v)
+                    self.db.conn.execute(
+                        'INSERT INTO preferences (key,val) VALUES (?,?)', (k, raw))
+                self.db.conn.commit()
+                self.clear()
+                self.update(d)
+        except:
+            import traceback
+            traceback.print_exc()

src/calibre/library/restore.py

@@ -101,6 +101,7 @@ class Restore(Thread):
             with TemporaryDirectory('_library_restore') as tdir:
                 self.library_path = tdir
                 self.scan_library()
+                self.load_preferences()
                 self.create_cc_metadata()
                 self.restore_books()
                 if self.successes == 0 and len(self.dirs) > 0:
@@ -109,6 +110,24 @@ class Restore(Thread):
         except:
             self.tb = traceback.format_exc()
 
+    def load_preferences(self):
+        self.progress_callback(None, 1)
+        self.progress_callback('Starting restore preferences', 0)
+        dbpath = os.path.join(self.src_library_path, 'metadata_db_prefs_backup.json')
+        ndbpath = os.path.join(self.library_path, 'metadata_db_prefs_backup.json')
+        if not os.path.exists(dbpath):
+            self.progress_callback('Cannot restore preferences. Backup file not found.', 1)
+            return
+        try:
+            shutil.copyfile(dbpath, ndbpath)
+            db = RestoreDatabase(self.library_path)
+            db.prefs.read_serialized(self.library_path)
+            db.commit()
+            db.conn.close()
+            self.progress_callback('Finished restore preferences', 1)
+        except:
+            self.progress_callback('Restoring preferences failed', 1)
+
     def scan_library(self):
         for dirpath, dirnames, filenames in os.walk(self.src_library_path):
             leaf = os.path.basename(dirpath)