[PATCH 1/5] Issue 4840: Make Translator/Performer/Engraver abstract base classes

[David Kastrup]

It does not make sense for them to be instantiable.
---
 lily/engraver.cc                | 17 -----------------
 lily/include/engraver.hh        |  3 ++-
 lily/include/performer.hh       |  2 +-
 lily/include/scheme-engraver.hh |  3 +++
 lily/include/translator.hh      |  9 ++++++++-
 lily/include/translator.icc     |  2 +-
 lily/translator.cc              | 14 +-------------
 7 files changed, 16 insertions(+), 34 deletions(-)

diff --git a/lily/engraver.cc b/lily/engraver.cc
index 25ae579..5a14869 100644
--- a/lily/engraver.cc
+++ b/lily/engraver.cc
@@ -175,20 +175,3 @@ ly_is_grob_cause (SCM obj)
 {
   return unsmob<Grob> (obj) || unsmob<Stream_event> (obj) || scm_is_null (obj);
 }
-
-#include "translator.icc"
-
-ADD_TRANSLATOR (Engraver,
-                /* doc */
-                "Base class for engravers.  Does nothing, so it is not used.",
-
-                /* create */
-                "",
-
-                /* read */
-                "",
-
-                /* write */
-                ""
-               );
-
diff --git a/lily/include/engraver.hh b/lily/include/engraver.hh
index 956f493..1f7e31c 100644
--- a/lily/include/engraver.hh
+++ b/lily/include/engraver.hh
@@ -64,7 +64,8 @@ public:
   /**
      override other ctor
   */
-  TRANSLATOR_DECLARATIONS (Engraver);
+  DECLARE_CLASSNAME (Engraver);
+  Engraver ();
 };
 
 #define make_item(x, cause) internal_make_item (ly_symbol2scm (x), cause, x, 
__FILE__, __LINE__, __FUNCTION__)
diff --git a/lily/include/performer.hh b/lily/include/performer.hh
index a640e24..70354fd 100644
--- a/lily/include/performer.hh
+++ b/lily/include/performer.hh
@@ -30,7 +30,7 @@
 class Performer : public Translator
 {
 public:
-  VIRTUAL_COPY_CONSTRUCTOR (Translator, Performer);
+  DECLARE_CLASSNAME (Performer);
   friend class Performer_group;
   Performer_group *get_daddy_performer () const;
 
diff --git a/lily/include/scheme-engraver.hh b/lily/include/scheme-engraver.hh
index e22e572..d8265f9 100644
--- a/lily/include/scheme-engraver.hh
+++ b/lily/include/scheme-engraver.hh
@@ -48,6 +48,9 @@ protected:
 private:
   void acknowledge_grob_by_hash (Grob_info info, SCM iface_function_hash);
   void init_acknowledgers (SCM alist, SCM *hash);
+  // For now no description.  In future, something derived from the
+  // definition might make sense.
+  SCM translator_description () const { return SCM_EOL; }
 
   DECLARE_ACKNOWLEDGER (grob);
   DECLARE_END_ACKNOWLEDGER (grob);
diff --git a/lily/include/translator.hh b/lily/include/translator.hh
index 1182207..5a93564 100644
--- a/lily/include/translator.hh
+++ b/lily/include/translator.hh
@@ -105,6 +105,7 @@ private:
 public:
   Context *context () const { return daddy_context_; }
 
+  Translator ();
   Translator (Translator const &);
 
   SCM internal_get_property (SCM symbol) const;
@@ -128,7 +129,13 @@ public:
   Context *get_score_context () const;
   Global_context *get_global_context () const;
 
-  TRANSLATOR_DECLARATIONS (Translator);
+  DECLARE_CLASSNAME (Translator);
+  virtual Translator *clone () const = 0;
+  virtual void fetch_precomputable_methods (Callback methods[]) = 0;
+  virtual SCM get_listener_list () const = 0;
+  virtual SCM translator_description () const = 0;
+  virtual Grob_info_callback get_acknowledger (SCM sym) = 0;
+  virtual Grob_info_callback get_end_acknowledger (SCM sym) = 0;
 
 protected:                      // should be private.
   Context *daddy_context_;
diff --git a/lily/include/translator.icc b/lily/include/translator.icc
index 250a923..3b700d8 100644
--- a/lily/include/translator.icc
+++ b/lily/include/translator.icc
@@ -77,7 +77,7 @@
   DEFINE_ACKNOWLEDGERS(classname)                                       \
 
 #define ADD_TRANSLATOR(classname, desc, grobs, read, write)             \
-  ADD_TRANSLATOR_FAMILY (classname)                                     \
+  ADD_TRANSLATOR_FAMILY (classname);                                    \
   ADD_THIS_TRANSLATOR (classname);                                      \
   DEFINE_TRANSLATOR_DOC(classname, desc, grobs, read, write)            \
   DEFINE_TRANSLATOR_LISTENER_LIST(classname)                            \
diff --git a/lily/translator.cc b/lily/translator.cc
index 370f777..9c667a8 100644
--- a/lily/translator.cc
+++ b/lily/translator.cc
@@ -318,16 +318,4 @@ internal_event_assignment (Stream_event **old_ev, 
Stream_event *new_ev, const ch
     }
 }
 
-ADD_TRANSLATOR (Translator,
-                /* doc */
-                "Base class.  Not instantiated.",
-
-                /* create */
-                "",
-
-                /* read */
-                "",
-
-                /* write */
-                ""
-               );
+// Base class.  Not instantiated.  No ADD_TRANSLATOR call.
-- 
2.7.4