Improve performance when scrolling in TPS plot

Closes #44 (closed)

sohstationviewer/view/plotting/time_power_squared_dialog.py

@@ -280,6 +280,10 @@ class TimePowerSquaredWidget(plotting_widget.PlottingWidget):
         :param event: pick event - event when object of canvas is selected.
             The event happens before button_press_event.
         """
+        if event.mouseevent.name == 'scroll_event':
+            return
+        if event.mouseevent.button in ('up', 'down'):
+            return
         info_str = ""
         if event.artist in self.axes:
             xdata = event.mouseevent.xdata