Added some comments.

src/sas/qtgui/Plotting/Plotter.py

@@ -531,7 +531,9 @@ def onAddText(self):
         # MPL style names
         styles = ['normal', 'italic', 'oblique']
         # QFont::Style maps directly onto the above
-        mpl_font.set_style(styles[extra_font.style().value])
+        # Get an index of the font style which we can then lookup in the styles list.
+        font_index = extra_font.style().value
+        mpl_font.set_style(styles[font_index])
 
         if len(extra_text) > 0:
             new_text = self.ax.text(pos_x,
@@ -916,6 +918,8 @@ def onMplMouseDown(self, event):
         """
         Left button down and ready to drag
         """
+        # Before checking if this mouse click is a left click, we need to update the position of the mouse regardless as
+        # this may be needed by other events (e.g. adding text)
         try:
             self.x_click = float(event.xdata)  # / size_x
             self.y_click = float(event.ydata)  # / size_y