Allow the notification stack to be moved using DBus

lib/WindowManager.vala

@@ -167,6 +167,14 @@ namespace Gala {
          */
         public abstract void perform_action (ActionType type);
 
+        /**
+         * Tells the window manager to move the Notifications Stack down
+         * by the given number of points, to make room for menus.
+         *
+         * @param offset The number of points by which to move the notifications stack
+         */
+        public abstract void offset_notifications (int32 offset);
+
         /**
          * Moves the window to the given workspace.
          *

src/DBus.vala

@@ -86,6 +86,10 @@ namespace Gala {
             wm.perform_action (type);
         }
 
+        public void offset_notifications (int32 offset) throws DBusError, Error {
+            wm.offset_notifications (offset);
+        }
+
         private const double SATURATION_WEIGHT = 1.5;
         private const double WEIGHT_THRESHOLD = 1.0;
 

src/NotificationStack.vala

@@ -29,6 +29,7 @@ public class Gala.NotificationStack : Object {
     private const int WIDTH = 300;
 
     private int stack_y;
+    private int stack_y_offset;
     private int stack_width;
 
     public Meta.Display display { get; construct; }
@@ -99,7 +100,7 @@ public class Gala.NotificationStack : Object {
             notification_x_pos = 0;
         }
 
-        move_window (notification, notification_x_pos, stack_y + TOP_OFFSET + InternalUtils.scale_to_int (ADDITIONAL_MARGIN, scale));
+        move_window (notification, notification_x_pos, stack_y + TOP_OFFSET + InternalUtils.scale_to_int (stack_y_offset + ADDITIONAL_MARGIN, scale));
         notifications.insert (0, notification);
     }
 
@@ -114,7 +115,7 @@ public class Gala.NotificationStack : Object {
     }
 
     private void update_positions (bool animate, float scale, float add_y = 0.0f) {
-        var y = stack_y + TOP_OFFSET + add_y + InternalUtils.scale_to_int (ADDITIONAL_MARGIN, scale);
+        var y = stack_y + TOP_OFFSET + add_y + InternalUtils.scale_to_int (stack_y_offset + ADDITIONAL_MARGIN, scale);
         var i = notifications.size;
         var delay_step = i > 0 ? 150 / i : 0;
         var iterator = 0;
@@ -156,6 +157,11 @@ public class Gala.NotificationStack : Object {
         }
     }
 
+    public void offset_notifications (int32 offset) {
+        stack_y_offset = offset;
+        update_positions (true);
+    }
+
     public void destroy_notification (Meta.WindowActor notification, bool animate) {
         if (animate) {
             notification.save_easing_state ();

src/WindowManager.vala

@@ -1007,6 +1007,10 @@ namespace Gala {
             }
         }
 
+        public void offset_notifications (int32 offset) {
+            notification_stack.offset_notifications (offset);
+        }
+
         public override void show_window_menu (Meta.Window window, Meta.WindowMenuType menu, int x, int y) {
             switch (menu) {
                 case Meta.WindowMenuType.WM: