window: Maximize tiled windows when resizing to work area

Now that tiled windows are resizable, the user may grow a tiled
windows until it covers the entire work area. As this makes the
window state mostly indistinguishable from maximization, avoid
subtle differences by properly maximizing the window in that case.

https://bugzilla.gnome.org/show_bug.cgi?id=645153

src/core/window.c

@@ -6147,6 +6147,24 @@ update_resize (MetaWindow *window,
     g_get_current_time (&window->display->grab_last_moveresize_time);
 }
 
+static void
+maybe_maximize_tiled_window (MetaWindow *window)
+{
+  MetaRectangle work_area;
+  gint shake_threshold;
+
+  if (!META_WINDOW_TILED_SIDE_BY_SIDE (window))
+    return;
+
+  shake_threshold = meta_prefs_get_drag_threshold ();
+
+  meta_window_get_work_area_for_monitor (window,
+                                         window->tile_monitor_number,
+                                         &work_area);
+  if (window->rect.width >= work_area.width - shake_threshold)
+    meta_window_maximize (window, META_MAXIMIZE_BOTH);
+}
+
 void
 meta_window_update_resize (MetaWindow *window,
                            gboolean    snap,
@@ -6190,6 +6208,7 @@ end_grab_op (MetaWindow *window,
                          modifiers & CLUTTER_SHIFT_MASK,
                          x, y,
                          TRUE);
+          maybe_maximize_tiled_window (window);
         }
     }
   window->screen->preview_tile_mode = META_TILE_NONE;