backends: Delegate pointer confinements to an impl object

Split pointer confinements in 2 objects, one set from the upper layers
containing its definition, and another managed by the backend that
applies it.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1403>

src/backends/native/meta-pointer-constraint-native.h

@@ -0,0 +1,46 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+
+/*
+ * Copyright (C) 2020 Red Hat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ * Written by:
+ *     Carlos Garnacho <carlosg@gnome.org>
+ */
+
+#ifndef META_POINTER_CONSTRAINT_NATIVE_H
+#define META_POINTER_CONSTRAINT_NATIVE_H
+
+#include <glib-object.h>
+
+#include "clutter/clutter.h"
+#include "backends/meta-pointer-constraint.h"
+
+G_BEGIN_DECLS
+
+#define META_TYPE_POINTER_CONSTRAINT_IMPL_NATIVE (meta_pointer_constraint_impl_native_get_type ())
+G_DECLARE_FINAL_TYPE (MetaPointerConstraintImplNative,
+                      meta_pointer_constraint_impl_native,
+                      META, POINTER_CONSTRAINT_IMPL_NATIVE,
+                      MetaPointerConstraintImpl)
+
+MetaPointerConstraintImpl * meta_pointer_constraint_impl_native_new (MetaPointerConstraint *constraint_impl,
+                                                                     const cairo_region_t  *region);
+
+G_END_DECLS
+
+#endif /* META_POINTER_CONSTRAINT_NATIVE_H */