Issue 5167/6: Changes: show \markup xxx = ... \etc assignments

[lilypond.git] / lily / include / protected-scm.hh

diff --git a/lily/include/protected-scm.hh b/lily/include/protected-scm.hh
index d5a6463bc04d5d52df9489575e4469c06e9c4e95..db8a151ff558854e31ad52e421a74bba7ccb228b 100644 (file)
--- a/lily/include/protected-scm.hh
+++ b/lily/include/protected-scm.hh
@@ -1,9 +1,20 @@
 /*
-  protected-scm.hh -- declare Protected_scm
+  This file is part of LilyPond, the GNU music typesetter.
 
-  source file of the GNU LilyPond music typesetter
+  Copyright (C) 1998--2015 Han-Wen Nienhuys <hanwen@xs4all.nl>
 
-  (c) 1998--2009 Han-Wen Nienhuys <hanwen@xs4all.nl>
+  LilyPond 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 3 of the License, or
+  (at your option) any later version.
+
+  LilyPond 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 LilyPond.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #ifndef PROTECTED_SCM_HH
@@ -13,19 +24,37 @@
 
 /*
   Mix GUILE GC with C++ ctors and dtors.
+
+  This version is intended to be only used for variables of static
+  lifetime (which are not feasible to protect using the per-instance
+  mechanism of the smob classes) but possibly varying content.  As a
+  result, the protection mechanism being used is the irreversible
+  scm_permanent_object.  The destructor (typically called after the
+  end of program execution) does not free resources and consequently
+  does not require the memory subsystem to be still workable.  A
+  working memory subsystem is only required once a non-immediate
+  Scheme value is assigned to the variable.  Since creation of a
+  non-immediate Scheme value requires a working memory subsystem in
+  the first place, this is not really a restriction.
+
+  To avoid accidental creation of temporaries, the copy constructor is
+  made unavailable.
 */
 class Protected_scm
 {
   SCM object_;
+  static SCM list_;
+  static SCM last_;
+  Protected_scm (Protected_scm const &);
+  void protectify (SCM);
 public:
   Protected_scm ();
   Protected_scm (SCM);
-  Protected_scm (Protected_scm const &);
-  ~Protected_scm ();
   Protected_scm &operator = (SCM);
   Protected_scm &operator = (Protected_scm const &);
-  operator SCM () const;
-  SCM to_SCM () const;
+  operator const SCM & () const;
+  operator SCM & ();
+  bool is_bound () const;  // SCM_UNBNDP balks at Protected_scm
 };
 
 #endif /* PROTECTED_SCM_HH */