Refactor get/set_property to take the item as first argument

lily/fingering-engraver.cc

 /*
   This file is part of LilyPond, the GNU music typesetter.
 
   Copyright (C) 1998--2020 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.
 
@@ skipping 67 matching lines @@
 
 void
 Fingering_engraver::acknowledge_note_column (Grob_info inf)
 {
   /* set NoteColumn as parent */
   /* and X-align on main noteheads */
   for (vsize i = 0; i < fingerings_.size (); i++)
     {
       Grob *t = fingerings_[i];
       t->set_parent (inf.grob (), X_AXIS);
-      t->set_property ("X-align-on-main-noteheads", SCM_BOOL_T);
+      set_property (t, "X-align-on-main-noteheads", SCM_BOOL_T);
     }
 }
 
 void
 Fingering_engraver::process_music ()
 {
   for (vsize i = events_.size (); i--;)
     {
-      SCM dir = events_[i]->get_property ("direction");
+      SCM dir = get_property (events_[i], "direction");
       make_script (to_dir (dir), events_[i], i);
     }
 }
 
 void
 Fingering_engraver::make_script (Direction d, Stream_event *r, size_t i)
 {
   Item *fingering = make_item ("Fingering", r->self_scm ());
 
   /*
     We can't fold these definitions into define-grobs since
     fingerings for chords need different settings.
   */
   Side_position_interface::set_axis (fingering, Y_AXIS);
   Self_alignment_interface::set_aligned_on_parent (fingering, X_AXIS);
 
   /* See script-engraver.cc */
-  SCM priority = fingering->get_property ("script-priority");
+  SCM priority = get_property (fingering, "script-priority");
   if (!scm_is_number (priority))
     priority = scm_from_int (200); // TODO: Explain magic.
   priority = scm_sum (priority, scm_from_size_t (i));
-  fingering->set_property ("script-priority", priority);
+  set_property (fingering, "script-priority", priority);
 
   if (d)
-    fingering->set_property ("direction", scm_from_int (d));
-  else if (!is_direction (fingering->get_property_data ("direction")))
-    fingering->set_property ("direction", scm_from_int (UP));
+    set_property (fingering, "direction", scm_from_int (d));
+  else if (!is_direction (get_property_data (fingering, "direction")))
+    set_property (fingering, "direction", scm_from_int (UP));
 
   fingerings_.push_back (fingering);
 }
 
 void
 Fingering_engraver::stop_translation_timestep ()
 {
   fingerings_.clear ();
   events_.clear ();
 }
@@ skipping 19 matching lines @@
 
                 /* create */
                 "Fingering ",
 
                 /* read */
                 "",
 
                 /* write */
                 ""
                );