Fix tap and hold not working because Qt 5 does not deliver touch update events during a tap and hold when the finger position does not change.

src/calibre/gui2/viewer/gestures.py

@@ -173,6 +173,7 @@ class State(QObject):
             self.possible_gestures &= {Pinch}
 
         if boundary == 'end':
+            self.check_for_holds()
             self.finalize()
             self.clear()
         else: