meta-monitor-manager-xrandr.c: fix screen size

Only call meta_monitor_manager_xrandr_update_screen_size() when the
CRTCs have been, if necessary, disabled.  It is always safe and
sometimes required to call it in this state.  Previously, for instance,
we would not call it in this state when shrinking the screen size (e.g.,
when in fractional "scale-up" mode), but it is in fact required to call
it in this state when using fractional "scale-up" mode.

Author: jknockel

src/backends/x11/meta-monitor-manager-xrandr.c

@@ -669,7 +669,7 @@ apply_crtc_assignments (MetaMonitorManager *manager,
   if (!n_crtcs)
     goto out;
 
-  if (width > manager->screen_width || height > manager->screen_height)
+  if (width > 0 && height > 0)
     {
       meta_monitor_manager_xrandr_update_screen_size (manager_xrandr,
                                                       width, height,
@@ -791,13 +791,6 @@ apply_crtc_assignments (MetaMonitorManager *manager,
       output->is_primary = FALSE;
     }
 
-  if (width > 0 && height > 0)
-    {
-      meta_monitor_manager_xrandr_update_screen_size (manager_xrandr,
-                                                      width, height,
-                                                      avg_screen_scale);
-    }
-
 out:
   XUngrabServer (manager_xrandr->xdisplay);
   XFlush (manager_xrandr->xdisplay);