Switch keyboard modes when opening new files

src/calibre/gui2/tweak_book/boss.py

@@ -221,6 +221,7 @@ class Boss(QObject):
             c = current_container()
             editor.load_text(c.decode(c.open(name).read()))
         self.gui.central.show_editor(editor)
+        self.gui.keyboard.set_mode(syntax)
 
     def edit_file_requested(self, name, syntax, mime):
         if name in self.editors:

src/calibre/gui2/tweak_book/keyboard.py

@@ -31,7 +31,12 @@ class KeyboardManager(object):
             km.finalize()
 
     def set_mode(self, name):
+        try:
             km = self.modes[name]
+        except KeyError:
+            name = 'other'
+            km = self.modes[name]
+        if name != self.current_mode:
             for un, action in self.actions.iteritems():
                 keys = km.keys_map[un]
                 action.setShortcuts(list(keys))