Add a button ot the search preferences to clear search history. Fixes #8953 (Clear search items)

src/calibre/gui2/preferences/search.py

@@ -26,12 +26,19 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         r('limit_search_columns_to', prefs, setting=CommaSeparatedList)
         fl = gui.library_view.model().db.field_metadata.get_search_terms()
         self.opt_limit_search_columns_to.update_items_cache(fl)
+        self.clear_history_button.clicked.connect(self.clear_histories)
 
     def refresh_gui(self, gui):
         gui.search.search_as_you_type(config['search_as_you_type'])
         gui.library_view.model().set_highlight_only(config['highlight_search_matches'])
         gui.search.do_search()
 
+    def clear_histories(self, *args):
+        for key, val in config.defaults.iteritems():
+            if key.endswith('_search_history') and isinstance(val, list):
+                config[key] = []
+        self.gui.search.clear_history()
+
 if __name__ == '__main__':
     app = QApplication([])
     test_widget('Interface', 'Search')

src/calibre/gui2/preferences/search.ui

@@ -90,6 +90,16 @@
      </property>
     </spacer>
    </item>
+   <item row="4" column="0">
+    <widget class="QPushButton" name="clear_history_button">
+     <property name="toolTip">
+      <string>Clear search histories from all over calibre. Including the book list, e-book viewer, fetch news dialog, etc.</string>
+     </property>
+     <property name="text">
+      <string>Clear search &amp;histories</string>
+     </property>
+    </widget>
+   </item>
   </layout>
  </widget>
  <customwidgets>

src/calibre/gui2/search_box.py

@@ -114,6 +114,9 @@ class SearchBox2(QComboBox): # {{{
     def text(self):
         return self.currentText()
 
+    def clear_history(self, *args):
+        QComboBox.clear(self)
+
     def clear(self, emit_search=True):
         self.normalize_state()
         self.setEditText('')