get_page_width
Description:
Returns the page width in units of unit.
Note that this function takes orientation and margins into consideration. See [method@Gtk.PageSetup.get_paper_width].
Parameters:
| this | 
           a `GtkPageSetup`  | 
      
| unit | 
           the unit for the return value  | 
      
Returns:
| 
           the page width.  |