2003 -> 2004

[lilypond.git] / lily / bezier-bow.cc

diff --git a/lily/bezier-bow.cc b/lily/bezier-bow.cc
index 8a92e9ddf4cfedd11f116faf96f2ef01869a07a8..dfd290d499da749df681bd97dd3d9e17064f49a7 100644 (file)
--- a/lily/bezier-bow.cc
+++ b/lily/bezier-bow.cc
@@ -3,111 +3,70 @@
 
   source file of the GNU LilyPond music typesetter
 
-  (c) 1998--2000 Jan Nieuwenhuizen <janneke@gnu.org>
+  (c) 1998--2004 Jan Nieuwenhuizen <janneke@gnu.org>
 */
 
 #include <math.h>
+
 #include "bezier-bow.hh"
 #include "misc.hh"
 #include "bezier.hh"
-#include "dimensions.hh"
-#include "direction.hh"
-#include "debug.hh"
-#include "main.hh"
-#include "lily-guile.hh"
-#include "paper-def.hh"
 
 
-Bezier_bow::Bezier_bow (Array<Offset> encompass, Direction dir)
+static Real
+F0_1 (Real x)
 {
-  alpha_ = 0;
-  dir_ = dir;
-  encompass_ = encompass;
-  to_canonical_form ();
+  return 2 / M_PI * atan (M_PI * x / 2);
 }
 
-Bezier
-Bezier_bow::get_bezier () const
+Real
+slur_height (Real width, Real h_inf, Real r_0)
 {
-  Bezier rv = curve_;
-  if (dir_ == DOWN)
-    {
-      rv.flip (Y_AXIS);
-    }
-
-  rv.rotate (alpha_);
-  rv.translate (origin_);
-  
-  return rv;
+  return F0_1 (width * r_0 / h_inf) * h_inf;
 }
 
-void
-Bezier_bow::to_canonical_form ()
-{
-  origin_ = encompass_[0];
-  translate (&encompass_, -origin_);
-
-  Offset delta = encompass_.top () - encompass_[0];
-  alpha_ = delta.arg ();
-
-  rotate (&encompass_, -alpha_);
-  if (dir_ == DOWN)
-    {
-      flip (&encompass_, Y_AXIS);
-    }
-
-  while (encompass_.size () > 1 && encompass_[1][X_AXIS] <= 0.0)
-    {
-      programming_error ("Degenerate bow: infinite steepness reqd");
-      encompass_.del (1);
-    }
-
-  Real l = encompass_.top ()[X_AXIS];
-  while (encompass_.size () > 1 && encompass_.top (1)[X_AXIS] >= l)
-    {
-      programming_error ("Degenerate bow: infinite steepness reqd");
-      encompass_.del (encompass_.size ()-2);
-    }
-}
+  /*
+  For small w, the height should be proportional to w, for w ->
+  infinity, the height should rise to a limit asymptotically.
 
-void
-Bezier_bow::set_default_bezier (Real h_inf, Real r_0)
-{
-  curve_ = get_default_bezier (h_inf, r_0);
-}
+  Hence we take F (x) such that
+  F (0) = 0 , F' (0) = 1, and F (infty) = 1
+
+  and use
+
+  h = h_infinity * F (x * r_0 / h_infinity)
+
+  
+  Examples:
+
+  * F (x) = 2/pi * atan (pi x/2)
+
+  * F (x) 1/alpha * x^alpha / (1 + x^alpha)
+
+  * (etc.)
+
+  [with the 2nd recipe you can determine how quickly the conversion from
+  `small' slurs to `big' slurs occurs.]
+
+  Although this might seem cand_idates to SCM-ify, it is not all clear
+  which parameters (ie. h_inf, r_0, F (.)) should be candidates for
+  this.  At present h_inf and r_0 come from paper settings, but we did
+  no experiments for determining the best combinations of F, h_inf and
+  r_0.
+
+  */
 
-/*
-  See Documentation/programmer/fonts.doc
- */
 Bezier
-Bezier_bow::get_default_bezier (Real h_inf, Real r_0) const
+slur_shape (Real width, Real h_inf, Real r_0)
 {
-  Offset delta (encompass_.top ()[X_AXIS] - encompass_[0][X_AXIS], 0);
-  Real b = delta.length ();
-  Real height = get_default_height (h_inf, r_0, b);
-  // urg: scmify this?
+  Bezier curve;
+  Real height =  slur_height (width, h_inf, r_0);
   Real indent = height;
 
-  Bezier curve;
   curve.control_[0] = Offset (0, 0);
   curve.control_[1] = Offset (indent, height);
-  curve.control_[2] = Offset (b - indent, height);
-  curve.control_[3] = Offset (b, 0);
+  curve.control_[2] = Offset (width - indent, height);
+  curve.control_[3] = Offset (width, 0);
   return curve;
 }
 
-/*
-  See Documentation/programmer/fonts.doc
- */
-Real
-Bezier_bow::get_default_height (Real h_inf, Real r_0, Real b) const
-{
-
-  SCM h = scm_eval (scm_listify (ly_symbol2scm ("slur-default-height"),
-                                gh_double2scm (h_inf),
-                                gh_double2scm (r_0),
-                                gh_double2scm (b),
-                                SCM_UNDEFINED));
-  return gh_scm2double (h);
-}
-