Add Select default and Set as default buttons to Configure metadata download screen to allow a user defined subset of fields to quickly restore to

src/calibre/ebooks/metadata/sources/base.py

@@ -21,6 +21,7 @@ from calibre.ebooks.metadata import check_isbn
 msprefs = JSONConfig('metadata_sources/global.json')
 msprefs.defaults['txt_comments'] = False
 msprefs.defaults['ignore_fields'] = []
+msprefs.defaults['user_default_ignore_fields'] = []
 msprefs.defaults['max_tags'] = 20
 msprefs.defaults['wait_after_first_identify_result'] = 30 # seconds
 msprefs.defaults['wait_after_first_cover_result'] = 60 # seconds

src/calibre/gui2/preferences/metadata_sources.py

@@ -224,6 +224,20 @@ class FieldsModel(QAbstractListModel): # {{{
             Qt.Unchecked])
         msprefs['ignore_fields'] = list(ignored_fields.union(changed))
 
+    def user_default_state(self, field):
+        return (Qt.Unchecked if field in msprefs.get('user_default_ignore_fields',[])
+                    else Qt.Checked)
+
+    def select_user_defaults(self):
+        self.overrides = dict([(f, self.user_default_state(f)) for f in self.fields])
+        self.reset()
+
+    def commit_user_defaults(self):
+        default_ignored_fields = set([x for x in msprefs['user_default_ignore_fields'] if x not in
+            self.overrides])
+        changed = set([k for k, v in self.overrides.iteritems() if v ==
+            Qt.Unchecked])
+        msprefs['user_default_ignore_fields'] = list(default_ignored_fields.union(changed))
 
 # }}}
 
@@ -286,6 +300,9 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         self.select_all_button.clicked.connect(self.changed_signal)
         self.clear_all_button.clicked.connect(self.fields_model.clear_all)
         self.clear_all_button.clicked.connect(self.changed_signal)
+        self.select_default_button.clicked.connect(self.fields_model.select_user_defaults)
+        self.select_default_button.clicked.connect(self.changed_signal)
+        self.set_as_default_button.clicked.connect(self.fields_model.commit_user_defaults)
 
     def configure_plugin(self):
         for index in self.sources_view.selectionModel().selectedRows():

src/calibre/gui2/preferences/metadata_sources.ui

@@ -102,6 +102,20 @@
             </property>
            </widget>
           </item>
+          <item row="2" column="0">
+           <widget class="QPushButton" name="select_default_button">
+            <property name="text">
+             <string>&amp;Select default</string>
+            </property>
+           </widget>
+          </item>
+          <item row="2" column="1">
+           <widget class="QPushButton" name="set_as_default_button">
+            <property name="text">
+             <string>&amp;Set as default</string>
+            </property>
+           </widget>
+          </item>
          </layout>
         </widget>
        </item>