enable the main window to remember its position on the screen

The genealogy -- as it were -- of this patch started with
https://gramps-project.org/bugs/view.php?id=5357 which was a
feature request for the clipboard to remember its location
on the screen, its placement, its position.

The p.r. https://github.com/gramps-project/gramps/pull/58
was a prototype implementation, but it also had the main
window remembering its location.  Then p.r. 58 turned into
https://github.com/gramps-project/gramps/pull/60/ -- but
later both of those were closed, never committed.

Since I really wanted the main window to be able to remember
its position, I have extracted the relevant code.  I also
modified it along the way, e.g. renaming some variables.

So all the credit should go to Sam Manzi, the originator of
those two pull requests, and thus the code in this commit.

However, any problems are due to me, my changes -- not Sam.

gramps/gen/config.py

@@ -224,6 +224,8 @@ register('interface.lds-width', 600)
 register('interface.location-height', 250)
 register('interface.location-width', 600)
 register('interface.main-window-height', 500)
+register('interface.main-window-horiz-position', 15)
+register('interface.main-window-vert-position', 10)
 register('interface.main-window-width', 775)
 register('interface.mapservice', 'OpenStreetMap')
 register('interface.media-height', 450)

gramps/gui/managedwindow.py

@@ -527,6 +527,7 @@ class ManagedWindow:
         """
         Set the dimensions of the window
         """
+        # self.width_key is set in the subclass, typically in its _local_init
         if self.width_key is not None:
             width = config.get(self.width_key)
             height = config.get(self.height_key)
@@ -536,6 +537,7 @@ class ManagedWindow:
         """
         Save the dimensions of the window to the config file
         """
+        # self.width_key is set in the subclass, typically in its _local_init
         if self.width_key is not None:
             (width, height) = self.window.get_size()
             config.set(self.width_key, width)

gramps/gui/viewmanager.py

@@ -356,10 +356,13 @@ class ViewManager(CLIManager):
         """
         width = config.get('interface.main-window-width')
         height = config.get('interface.main-window-height')
+        horiz_position = config.get('interface.main-window-horiz-position')
+        vert_position = config.get('interface.main-window-vert-position')
 
         self.window = Gtk.Window()
         self.window.set_icon_from_file(ICON)
         self.window.set_default_size(width, height)
+        self.window.move(horiz_position, vert_position)
 
         vbox = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
         self.window.add(vbox)
@@ -758,6 +761,10 @@ class ViewManager(CLIManager):
         (width, height) = self.window.get_size()
         config.set('interface.main-window-width', width)
         config.set('interface.main-window-height', height)
+        # save the current window position
+        (horiz_position, vert_position) = self.window.get_position()
+        config.set('interface.main-window-horiz-position', horiz_position)
+        config.set('interface.main-window-vert-position', vert_position)
         config.save()
         Gtk.main_quit()