Clear search histories in preferences should clear the fts dialog's search history as well

src/calibre/gui2/actions/fts.py

@@ -31,3 +31,7 @@ class FullTextSearchAction(InterfaceAction):
     def library_changed(self, db):
         if self._dialog is not None:
             self._dialog.library_changed()
+
+    def clear_search_history(self):
+        if self._dialog is not None:
+            self._dialog.clear_search_history()

src/calibre/gui2/fts/dialog.py

@@ -96,6 +96,9 @@ class FTSDialog(Dialog):
         self.scan_status.startup()
         self.results_panel.on_show()
 
+    def clear_search_history(self):
+        self.results_panel.clear_history()
+
 
 if __name__ == '__main__':
     from calibre.gui2 import Application

src/calibre/gui2/fts/search.py

@@ -497,6 +497,9 @@ class SearchInputPanel(QWidget):
 
         self.layout().addLayout(v2)
 
+    def clear_history(self):
+        self.search_box.clear_history()
+
     def start(self):
         self.pi.start()
 
@@ -777,6 +780,9 @@ class ResultsPanel(QWidget):
         if st is not None:
             s.restoreState(st)
 
+    def clear_history(self):
+        self.sip.clear_history()
+
     def remove_book_from_results(self, book_id):
         self.results_view.m.remove_book(book_id)
 

src/calibre/gui2/preferences/search.py

@@ -253,12 +253,16 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         for key in (
             'bulk_edit_search_for', 'bulk_edit_replace_with',
             'viewer-highlights-search-panel-expression',
-            'viewer-search-panel-expression',
+            'viewer-search-panel-expression', 'library-fts-search-box',
         ):
             history.set('lineedit_history_' + key, [])
         from calibre.gui2.viewer.config import vprefs
         for k in ('search', 'highlights'):
             vprefs.set(f'saved-{k}-settings', {})
+        from calibre.gui2.ui import get_gui
+        gui = get_gui()
+        if gui is not None:
+            gui.iactions['Full Text Search'].clear_search_history()
 
 
 if __name__ == '__main__':