Show time label on top of ruler

Closes #71 (closed)

sohstationviewer/view/plotting/plotting_widget/plotting_widget.py

 """
 Class of which object is used to plot data
 """
+from typing import Optional
+
+import matplotlib.text
 import numpy as np
-from PySide2.QtCore import QTimer
+from PySide2.QtCore import QTimer, Qt
 from matplotlib import pyplot as pl
 from PySide2 import QtCore, QtWidgets
 
@@ -10,7 +13,8 @@ from sohstationviewer.conf import constants
 from sohstationviewer.view.util.color import set_color_mode
 from sohstationviewer.view.util.functions import get_total_miny_maxy
 from sohstationviewer.view.plotting.plotting_widget.plotting_axes import (
-    PlottingAxes)
+    PlottingAxes
+)
 from sohstationviewer.view.plotting.plotting_widget.plotting import Plotting
 
 from sohstationviewer.controller.plotting_data import format_time
@@ -200,6 +204,10 @@ class PlottingWidget(QtWidgets.QScrollArea):
         self.plotting = Plotting(self, self.plotting_axes,
                                  parent_params=parent)
 
+        self.new_min_x = float('-inf')
+
+        self.ruler_text: Optional[matplotlib.text.Text] = None
+
         self.set_colors('B')
 
     # ======================================================================= #
@@ -254,10 +262,10 @@ class PlottingWidget(QtWidgets.QScrollArea):
 
         :param xdata: float - time value in plot
         """
-        if self.min_x == xdata:
+        if self.new_min_x == xdata:
             return
         self.zoom_marker1_shown = False
-        [self.min_x, self.max_x] = sorted([self.min_x, xdata])
+        [self.min_x, self.max_x] = sorted([self.new_min_x, xdata])
         self.set_lim()
         self.zoom_marker1.set_visible(False)
         self.zoom_marker2.set_visible(False)
@@ -332,6 +340,16 @@ class PlottingWidget(QtWidgets.QScrollArea):
         else:
             xdata = self.get_timestamp(event)
 
+        # We only want to remove the text on the ruler when we start zooming in
+        # or move the ruler to another location.
+        if modifiers in [QtCore.Qt.ControlModifier, QtCore.Qt.MetaModifier,
+                         Qt.ShiftModifier]:
+            try:
+                self.ruler_text.remove()
+                self.ruler_text = None
+            except AttributeError:
+                pass
+
         for w in self.peer_plotting_widgets:
             if modifiers == QtCore.Qt.ShiftModifier:
                 w.on_shift_click(xdata)
@@ -340,6 +358,10 @@ class PlottingWidget(QtWidgets.QScrollArea):
                 w.on_ctrl_cmd_click(xdata)
             w.draw()
 
+        self.parent.show()
+        self.parent.activateWindow()
+        self.parent.raise_()
+
     def on_ctrl_cmd_click(self, xdata):
         """
         On ctrl/cmd + left click
@@ -356,6 +378,15 @@ class PlottingWidget(QtWidgets.QScrollArea):
         except AttributeError:
             pass
         self.set_ruler_visibled(self.ruler, xdata)
+        if xdata >= self.min_x:
+            self.ruler_text = self.plotting_axes.fig.text(
+                xdata, 75, 'Potato',
+                verticalalignment='top',
+                horizontalalignment='center',
+                transform=self.timestamp_bar_top.transData,
+                color=self.display_color['basic'],
+                size=self.timestamp_bar_top.get_xticklabels()[0].get_fontsize()
+            )
 
     def on_shift_click(self, xdata):
         """
@@ -373,7 +404,7 @@ class PlottingWidget(QtWidgets.QScrollArea):
         if not self.zoom_marker1_shown:
             self.ruler.set_visible(False)
             self.set_ruler_visibled(self.zoom_marker1, xdata)
-            self.min_x = xdata
+            self.new_min_x = xdata
             self.zoom_marker1_shown = True
         else:
             self.set_ruler_visibled(self.zoom_marker2, xdata)