Make tag browser filtering work when capital letters are entered.

src/calibre/gui2/tag_browser/model.py

@@ -840,6 +840,15 @@ def _get_category_nodes(self, sort):
                 self.categories[category] = tb_categories[category]['name']
         return data
 
+    def set_categories_filter(self, txt):
+        if txt:
+            self.filter_categories_by = icu_lower(txt)
+        else:
+            self.filter_categories_by = None
+
+    def get_categories_filter(self):
+        return self.filter_categories_by
+
     def refresh(self, data=None):
         '''
         Here to trap usages of refresh in the old architecture. Can eventually

src/calibre/gui2/tag_browser/ui.py

@@ -443,12 +443,12 @@ def find(self):
         txt = unicode(self.item_search.currentText()).strip()
 
         if txt.startswith('*'):
-            model.filter_categories_by = txt[1:]
+            model.set_categories_filter(txt[1:])
             self.tags_view.recount()
             self.current_find_position = None
             return
-        if model.filter_categories_by:
-            model.filter_categories_by = None
+        if model.get_categories_filter():
+            model.set_categories_filter(None)
             self.tags_view.recount()
             self.current_find_position = None
 

src/calibre/gui2/tag_browser/view.py

@@ -302,7 +302,7 @@ def context_menu_handler(self, action=None, category=None,
                 self.hidden_categories.clear()
             self.db.prefs.set('tag_browser_hidden_categories', list(self.hidden_categories))
             if reset_filter_categories:
-                self._model.filter_categories_by = None
+                self._model.set_categories_filter(None)
             self._model.rebuild_node_tree()
         except:
             return