zoom out

closes #177 (closed) #281 (closed)

• Shift+Click will zoom out for all windows by undoing a zoom in. Notice that in TPS, the task of zoom in/out is done by moving zoom markers to the corresponding position.
• Ruler marker and its text will stay at its corresponding position either with zoom in/out.
• When adding/removing a channel only the current window will be replotted with the last zoom range. (Please test on Q330 5244.sdr's VEP to see if the result is acceptable)

sohstationviewer/view/plotting/plotting_widget/plotting_widget.py

@@ -364,9 +364,9 @@ class PlottingWidget(QtWidgets.QScrollArea):
             self.min_x, self.max_x = self.zoom_minmax_list[-2]
             self.zoom_minmax_list.pop()
             self.set_lim(is_zoom_in=False)
-            self.zoom_marker1.set_visible(False)
-            self.zoom_marker2.set_visible(False)
-            self.plotting_axes.canvas.draw()
+        self.zoom_marker1.set_visible(False)
+        self.zoom_marker2.set_visible(False)
+        self.plotting_axes.canvas.draw()
 
     def eventFilter(self, target: QObject, event: QEvent) -> bool:
         """