Show time label on top of ruler

Closes #71 (closed)

sohstationviewer/view/plotting/plotting_widget/plotting_widget.py

@@ -357,6 +357,13 @@ class PlottingWidget(QtWidgets.QScrollArea):
                 pass
 
         for w in self.peer_plotting_widgets:
+            if modifiers in [QtCore.Qt.ControlModifier, QtCore.Qt.MetaModifier,
+                             Qt.ShiftModifier]:
+                try:
+                    w.ruler_text.remove()
+                    w.ruler_text = None
+                except AttributeError:
+                    pass
             if modifiers == QtCore.Qt.ShiftModifier:
                 w.on_shift_click(xdata)
             elif modifiers in [QtCore.Qt.ControlModifier,