Add to preferences/look & feel a list of fields for which items are hierarchical.

src/calibre/gui2/preferences/look_feel.py

@@ -7,17 +7,19 @@ __docformat__ = 'restructuredtext en'
 
 from PyQt4.Qt import QApplication, QFont, QFontInfo, QFontDialog
 
-from calibre.gui2.preferences import ConfigWidgetBase, test_widget
+from calibre.gui2.preferences import ConfigWidgetBase, test_widget, CommaSeparatedList
 from calibre.gui2.preferences.look_feel_ui import Ui_Form
 from calibre.gui2 import config, gprefs, qt_app
 from calibre.utils.localization import available_translations, \
     get_language, get_lang
 from calibre.utils.config import prefs
+from calibre.utils.icu import sort_key
 
 class ConfigWidget(ConfigWidgetBase, Ui_Form):
 
     def genesis(self, gui):
         self.gui = gui
+        db = gui.library_view.model().db
 
         r = self.register
 
@@ -61,6 +63,15 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         r('tags_browser_partition_method', gprefs, choices=choices)
         r('tags_browser_collapse_at', gprefs)
 
+        choices = set([k for k in db.field_metadata.all_field_keys()
+                    if db.field_metadata[k]['is_category'] and
+                       db.field_metadata[k]['datatype'] in ['text', 'series', 'enumeration']])
+        choices -= set(['authors', 'publisher', 'formats', 'news'])
+        self.opt_categories_using_hierarchy.update_items_cache(choices)
+        r('categories_using_hierarchy', db.prefs, setting=CommaSeparatedList,
+          choices=sorted(list(choices), key=sort_key))
+
+
         self.current_font = None
         self.change_font_button.clicked.connect(self.change_font)
 

src/calibre/gui2/preferences/look_feel.ui

@@ -190,6 +190,28 @@ up into sub-categories. If the partition method is set to disable, this value is
      </item>
     </layout>
    </item>
+   <item row="8" column="0">
+    <widget class="QLabel" name="label_81">
+     <property name="text">
+      <string>Categories with hierarchical items:</string>
+     </property>
+     <property name="buddy">
+      <cstring>opt_categories_using_hierarchy</cstring>
+     </property>
+    </widget>
+   </item>
+   <item row="8" column="1">
+    <widget class="MultiCompleteLineEdit" name="opt_categories_using_hierarchy">
+     <property name="toolTip">
+      <string>A comma-separated list of columns in which items containing
+periods are displayed in the tag browser trees. For example, if
+this box contains 'tags' then tags of the form 'mystery.English'
+and 'mystery.Thriller' will be displayed with English and Thriller
+both under the label 'mystery'. If 'tags' is not in this box,
+then the tags will be displayed each on their own line.</string>
+     </property>
+    </widget>
+   </item>
    <item row="15" column="0" colspan="2">
     <widget class="QGroupBox" name="groupBox_2">
      <property name="title">
@@ -275,6 +297,13 @@ up into sub-categories. If the partition method is set to disable, this value is
    </item>
   </layout>
  </widget>
+ <customwidgets>
+  <customwidget>
+   <class>MultiCompleteLineEdit</class>
+   <extends>QLineEdit</extends>
+   <header>calibre/gui2/complete.h</header>
+  </customwidget>
+ </customwidgets>
  <resources/>
  <connections/>
 </ui>

src/calibre/gui2/tag_view.py

@@ -914,7 +914,8 @@ class TagsModel(QAbstractItemModel): # {{{
                     node_parent = category
 
                 components = [t for t in tag.name.split('.')]
-                if key in ['authors', 'publisher', 'title'] or len(components) == 1 or \
+                if key not in self.db.prefs.get('categories_using_hierarchy', []) \
+                        or len(components) == 1 or \
                         self.db.field_metadata[key]['kind'] == 'user':
                     self.beginInsertRows(category_index, 999999, 1)
                     TagTreeItem(parent=node_parent, data=tag, tooltip=tt,

src/calibre/library/database2.py

@@ -174,6 +174,7 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
         self.prefs = DBPrefs(self)
         defs = self.prefs.defaults
         defs['gui_restriction'] = defs['cs_restriction'] = ''
+        defs['categories_using_hierarchy'] = ''
 
         # Migrate saved search and user categories to db preference scheme
         def migrate_preference(key, default):