Allow customizing the text that appears below covers in the cover grid

You can now show any metadata field below the covers in the cover grid
view, not just title. To change the displayed field go to
Preferences->Look & Feel->Cover Grid.

src/calibre/db/backend.py

@@ -428,6 +428,7 @@ class DB(object):
         defs['virtual_lib_on_startup'] = defs['cs_virtual_lib_on_startup'] = ''
         defs['virt_libs_hidden'] = defs['virt_libs_order'] = ()
         defs['update_all_last_mod_dates_on_start'] = False
+        defs['field_under_covers_in_grid'] = 'title'
 
         # Migrate the bool tristate tweak
         defs['bools_are_tristate'] = \

src/calibre/gui2/library/alternate_views.py

@@ -20,7 +20,8 @@ from PyQt4.Qt import (
     QPropertyAnimation, QEasingCurve, pyqtSlot, QHelpEvent, QAbstractItemView,
     QStyleOptionViewItem, QToolTip, QByteArray, QBuffer, QBrush)
 
-from calibre import fit_image, prints, prepare_string_for_xml
+from calibre import fit_image, prints, prepare_string_for_xml, human_readable
+from calibre.constants import DEBUG
 from calibre.ebooks.metadata import fmt_sidx
 from calibre.utils import join_with_timeout
 from calibre.gui2 import gprefs, config
@@ -369,6 +370,23 @@ class CoverDelegate(QStyledItemDelegate):
     def sizeHint(self, option, index):
         return self.item_size
 
+    def render_field(self, db, book_id):
+        try:
+            field = db.pref('field_under_covers_in_grid', 'title')
+            if field == 'size':
+                ans = human_readable(db.field_for(field, book_id, default_value=0))
+            else:
+                mi = db.get_proxy_metadata(book_id)
+                display_name, ans, val, fm = mi.format_field_extended(field)
+                if fm and fm['datatype'] == 'rating':
+                    ans = u'\u2605' * int(val/2.0)
+            return unicode(ans)
+        except Exception:
+            if DEBUG:
+                import traceback
+                traceback.print_exc()
+        return ''
+
     def paint(self, painter, option, index):
         QStyledItemDelegate.paint(self, painter, option, QModelIndex())  # draw the hover and selection highlights
         m = index.model()
@@ -418,7 +436,7 @@ class CoverDelegate(QStyledItemDelegate):
                     rect = trect
                     rect.setTop(rect.bottom() - self.title_height + 5)
                     painter.setRenderHint(QPainter.TextAntialiasing, True)
-                    title = db.field_for('title', book_id, default_value='')
+                    title = self.render_field(db, book_id)
                     metrics = painter.fontMetrics()
                     painter.drawText(rect, Qt.AlignCenter|Qt.TextSingleLine,
                                      metrics.elidedText(title, Qt.ElideRight, rect.width()))

src/calibre/gui2/preferences/look_feel.py

@@ -212,6 +212,11 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         r('categories_using_hierarchy', db.prefs, setting=CommaSeparatedList,
           choices=sorted(list(choices), key=sort_key))
 
+        fm = db.field_metadata
+        choices = sorted(((fm[k]['name'], k) for k in fm.displayable_field_keys() if fm[k]['name']),
+                         key=lambda x:sort_key(x[0]))
+        r('field_under_covers_in_grid', db.prefs, choices=choices)
+
         self.current_font = self.initial_font = None
         self.change_font_button.clicked.connect(self.change_font)
 

src/calibre/gui2/preferences/look_feel.ui

@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>820</width>
-    <height>519</height>
+    <height>546</height>
    </rect>
   </property>
   <property name="windowTitle">
@@ -261,10 +261,40 @@
        <item>
         <widget class="QCheckBox" name="opt_cover_grid_show_title">
          <property name="text">
-          <string>Show the book &amp;title below the cover</string>
+          <string>Show a field (such as title) &amp;under the covers</string>
          </property>
         </widget>
        </item>
+       <item>
+        <layout class="QHBoxLayout" name="horizontalLayout_2">
+         <item>
+          <widget class="QLabel" name="label_14">
+           <property name="text">
+            <string>&amp;Field to show under the covers:</string>
+           </property>
+           <property name="buddy">
+            <cstring>opt_field_under_covers_in_grid</cstring>
+           </property>
+          </widget>
+         </item>
+         <item>
+          <widget class="QComboBox" name="opt_field_under_covers_in_grid"/>
+         </item>
+         <item>
+          <spacer name="horizontalSpacer_2">
+           <property name="orientation">
+            <enum>Qt::Horizontal</enum>
+           </property>
+           <property name="sizeHint" stdset="0">
+            <size>
+             <width>40</width>
+             <height>20</height>
+            </size>
+           </property>
+          </spacer>
+         </item>
+        </layout>
+       </item>
        <item>
         <layout class="QHBoxLayout" name="horizontalLayout_3">
          <item>
@@ -926,5 +956,22 @@ a few top-level elements.</string>
  <resources>
   <include location="../../../../resources/images.qrc"/>
  </resources>
- <connections/>
+ <connections>
+  <connection>
+   <sender>opt_cover_grid_show_title</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>opt_field_under_covers_in_grid</receiver>
+   <slot>setEnabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>75</x>
+     <y>102</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>289</x>
+     <y>118</y>
+    </hint>
+   </hints>
+  </connection>
+ </connections>
 </ui>