Refactor get/set_property to take the item as first argument

lily/arpeggio.cc

 /*
   This file is part of LilyPond, the GNU music typesetter.
 
   Copyright (C) 2000--2020 Jan Nieuwenhuizen <janneke@gnu.org>
 
   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 99 matching lines @@
   heads *= 1 / Staff_symbol_referencer::staff_space (me);
 
   return ly_interval2scm (heads);
 }
 
 MAKE_SCHEME_CALLBACK (Arpeggio, print, 1);
 SCM
 Arpeggio::print (SCM smob)
 {
   Grob *me = unsmob<Grob> (smob);
-  Interval heads = robust_scm2interval (me->get_property ("positions"),
+  Interval heads = robust_scm2interval (get_property (me, "positions"),
                                         Interval ())
                    * Staff_symbol_referencer::staff_space (me);
 
   if (heads.is_empty () || heads.length () < 0.5)
     {
-      if (to_boolean (me->get_property ("transparent")))
+      if (to_boolean (get_property (me, "transparent")))
         {
           /*
             This is part of a cross-staff/-voice span-arpeggio,
             so we need to ensure `heads' is large enough to encompass
             a single trill-element since the span-arpeggio depends on
             its children to prevent collisions.
           */
           heads.unite (get_squiggle (me).extent (Y_AXIS));
         }
       else
         {
           me->warning (_ ("no heads for arpeggio found?"));
           me->suicide ();
           return SCM_EOL;
         }
     }
 
-  SCM ad = me->get_property ("arpeggio-direction");
+  SCM ad = get_property (me, "arpeggio-direction");
   Direction dir = CENTER;
   if (is_direction (ad))
     dir = to_dir (ad);
 
   Stencil mol;
   Stencil squiggle (get_squiggle (me));
 
   /*
     Compensate for rounding error which may occur when a chord
     reaches the center line, resulting in an extra squiggle
@@ skipping 23 matching lines @@
 }
 
 /* Draws a vertical bracket to the left of a chord
    Chris Jackson <chris@fluffhouse.org.uk> */
 
 MAKE_SCHEME_CALLBACK (Arpeggio, brew_chord_bracket, 1);
 SCM
 Arpeggio::brew_chord_bracket (SCM smob)
 {
   Grob *me = unsmob<Grob> (smob);
-  Interval heads = robust_scm2interval (me->get_property ("positions"),
+  Interval heads = robust_scm2interval (get_property (me, "positions"),
                                         Interval ())
                    * Staff_symbol_referencer::staff_space (me);
 
   Real th
     = me->layout ()->get_dimension (ly_symbol2scm ("line-thickness"))
-      * robust_scm2double (me->get_property ("thickness"), 1);
+      * robust_scm2double (get_property (me, "thickness"), 1);
   Real sp = 1.5 * Staff_symbol_referencer::staff_space (me);
   Real dy = heads.length () + sp;
-  Real x = robust_scm2double (me->get_property ("protrusion"), 0.4);
+  Real x = robust_scm2double (get_property (me, "protrusion"), 0.4);
 
   Stencil mol (Lookup::bracket (Y_AXIS, Interval (0, dy), th, x, th));
   mol.translate_axis (heads[LEFT] - sp / 2.0, Y_AXIS);
   return mol.smobbed_copy ();
 }
 
 MAKE_SCHEME_CALLBACK (Arpeggio, brew_chord_slur, 1);
 SCM
 Arpeggio::brew_chord_slur (SCM smob)
 {
   Grob *me = unsmob<Grob> (smob);
-  SCM dash_definition = me->get_property ("dash-definition");
-  Interval heads = robust_scm2interval (me->get_property ("positions"),
+  SCM dash_definition = get_property (me, "dash-definition");
+  Interval heads = robust_scm2interval (get_property (me, "positions"),
                                         Interval ())
                    * Staff_symbol_referencer::staff_space (me);
 
   Real lt
     = me->layout ()->get_dimension (ly_symbol2scm ("line-thickness"))
-      * robust_scm2double (me->get_property ("line-thickness"), 1.0);
+      * robust_scm2double (get_property (me, "line-thickness"), 1.0);
   Real th
     = me->layout ()->get_dimension (ly_symbol2scm ("line-thickness"))
-      * robust_scm2double (me->get_property ("thickness"), 1.0);
+      * robust_scm2double (get_property (me, "thickness"), 1.0);
   Real dy = heads.length ();
 
   Real height_limit = 1.5;
   Real ratio = .33;
   Bezier curve = slur_shape (dy, height_limit, ratio);
   curve.rotate (90.0);
 
   Stencil mol (Lookup::slur (curve, th, lt, dash_definition));
   mol.translate_axis (heads[LEFT], Y_AXIS);
   return mol.smobbed_copy ();
 }
 
 /*
   We have to do a callback, because print () triggers a
   vertical alignment if it is cross-staff.
 */
 MAKE_SCHEME_CALLBACK (Arpeggio, width, 1);
 SCM
 Arpeggio::width (SCM smob)
 {
   Grob *me = unsmob<Grob> (smob);
   return ly_interval2scm (get_squiggle (me).extent (X_AXIS));
 }
 
 MAKE_SCHEME_CALLBACK (Arpeggio, pure_height, 3);
 SCM
 Arpeggio::pure_height (SCM smob, SCM, SCM)
 {
   Grob *me = unsmob<Grob> (smob);
-  if (to_boolean (me->get_property ("cross-staff")))
+  if (to_boolean (get_property (me, "cross-staff")))
     return ly_interval2scm (Interval ());
 
   return Grob::stencil_height (smob);
 }
 
 ADD_INTERFACE (Arpeggio,
                "Functions and settings for drawing an arpeggio symbol.",
 
                /* properties */
                "arpeggio-direction "
                "dash-definition " // TODO: make apply to non-slur arpeggios
                "line-thickness "
                "positions "
                "protrusion "
                "script-priority " // TODO: make around-note-interface
                "stems "
                "thickness "
               );