Move layoutEngine ownership to NSWindow

Source/NSWindowPrivate.h

@@ -0,0 +1,36 @@
+/* Copyright (C) 2023 Free Software Foundation, Inc.
+   
+   By: Benjamin Johnson
+   Date: 28-2-2023
+   This file is part of the GNUstep Library.
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+   
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+   
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free
+   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02110 USA.
+*/
+
+#ifndef _GNUstep_H_NSWindowPrivate
+#define _GNUstep_H_NSWindowPrivate
+
+#import "AppKit/NSWindow.h"
+
+@interface NSWindow (NSConstraintBasedLayoutCorePrivateMethods)
+
+- (GSAutoLayoutEngine*) _layoutEngine;
+
+- (void) _setLayoutEngine: (GSAutoLayoutEngine*)layoutEngine;
+
+@end
+
+#endif // _GNUstep_H_NSWindowPrivate