Avoid use of global for testing purpose

Author: Saumya-Mishra9129

StarChart.py

@@ -764,8 +764,7 @@ def get_planet_index(name):
 #
 # controls on menubar1 (_('what')):
 fullscreen = ToolButton('view-fullscreen')
-button1 = ToggleToolButton(icon_name='night-off')
-button1.set_tooltip(_('Night Vision'))
+
 button2 = ToggleToolButton(icon_name='invert-off')
 button2.set_tooltip(_('Invert Display'))
 button3 = ToggleToolButton(icon_name='left-right')
@@ -1077,6 +1076,10 @@ def __init__(self, context):
                         Gdk.EventMask.BUTTON1_MOTION_MASK | Gdk.EventMask.BUTTON2_MOTION_MASK)
         self.connect('button_press_event', self.pressing)
         self.magnifying = False
+        self.nightvision = False
+        starchart = StarChart()
+        self.button1 = starchart.button1
+
         self.mag_center = [0, 0]
         if (not specifytime):
             GObject.timeout_add(60000, self.timer1_cb)
@@ -1195,8 +1198,9 @@ def callback(self, widget, data=None):
         if (data == None):
             return False
         elif (data == 'night vision'):
-            self.nightvision = button1.get_active()
-            button1.set_active(self.nightvision)
+
+            self.nightvision = self.button1.get_active()
+            self.button1.set_active(self.nightvision)
             self.plotchart()
             return False
         elif (data == 'invert display'):
@@ -3041,12 +3045,15 @@ def __init__(self, handle):
 
         # Fill the toolbox bars
 
+        self.button1 = ToggleToolButton(icon_name='night-off')
+        self.button1.set_tooltip(_('Night Vision'))
+
         self._toolbar_add(self.what_toolbar, fullscreen)
         separator = Gtk.SeparatorToolItem()
         separator.props.draw = True
         separator.set_expand(False)
         self._toolbar_add(self.what_toolbar, separator)
-        self._toolbar_add(self.what_toolbar, button1)
+        self._toolbar_add(self.what_toolbar, self.button1)
         self._toolbar_add(self.what_toolbar, button2)
         self._toolbar_add(self.what_toolbar, button3)
         self._toolbar_add(self.what_toolbar, button4)
@@ -3169,7 +3176,7 @@ def __init__(self, handle):
         # Connect the control widget events.
         self.nightvision = False
         fullscreen.connect('clicked', self._fullscreen_callback)
-        button1.connect('clicked', self.chart.callback, 'night vision')
+        self.button1.connect('clicked', self.chart.callback, 'night vision')
         button2.connect('clicked', self.chart.callback, 'invert display')
         button3.connect('clicked', self.chart.callback, 'flip horizontally')
         button4.connect('clicked', self.chart.callback, 'draw constellations')
@@ -3260,6 +3267,7 @@ def read_file(self, filename):
             else:
                 zoneoffset = zoneoffset + mm
         initialize_controls()
+        self.nightvision = False
         self.chart.plotchart()
 
     def write_file(self, filename):