Fix #888: Add ly:stencil-scale.

* input/regression/stencil-scale.ly

  new regtest for testing ly:stencil-scale

* lily/stencil-interpret.cc (interpret_stencil_expression):

  interpret new stencil command `scale-stencil', unscaling offset of body to
  compensate for change in output scale

* lily/stencil-scheme.cc (ly_stencil_scale):

  export new function `ly:stencil-scale'

* lily/stencil.cc, include/stencil.hh (scale):

  new method for scaling stencils

* scm/define-markup-commands.scm (scale):

  new markup command

* scm/define-stencil-commands.scm

  (ly:all-stencil-commands): add stencil commands for setting and resetting
  scale (`setscale', `resetscale')

  (ly:all-output-backend-commands): add `scale-stencil' command

* scm/output-ps.scm, output-svg.scm (setscale, resetscale):

  implement stencil outputters for scaling

1 files changed, 16 insertions, 0 deletions

diff --git a/lily/stencil-interpret.cc b/lily/stencil-interpret.cc
index 509c89aba4..6985f2bbf0 100644
--- a/lily/stencil-interpret.cc
+++ b/lily/stencil-interpret.cc
@@ -88,6 +88,22 @@ interpret_stencil_expression (SCM expr,
 
 	  return;
 	}
+      else if (head == ly_symbol2scm ("scale-stencil"))
+	{
+	  SCM args = scm_cadr (expr);
+	  SCM x_scale = scm_car (args);
+	  SCM y_scale = scm_cadr (args);
+	  Offset unscaled = o.scale (Offset (1 / scm_to_double (x_scale),
+					     1 / scm_to_double (y_scale)));
+
+	  (*func) (func_arg, scm_list_3 (ly_symbol2scm ("setscale"), x_scale,
+					 y_scale));
+	  interpret_stencil_expression (scm_caddr (expr), func, func_arg,
+					unscaled);
+	  (*func) (func_arg, scm_list_1 (ly_symbol2scm ("resetscale")));
+
+	  return;
+	}
       else
 	{
 	  (*func) (func_arg,