From 37319a0900a937282a04fa433bc0c62d234f7128 Mon Sep 17 00:00:00 2001
From: Reinhold Kainhofer <reinhold@kainhofer.com>
Date: Thu, 11 Sep 2008 22:20:59 +0200
Subject: [PATCH] Add ly:staff-symbol-line-thickness Scheme-callback, returning
 line thickness

-) Add a callback ly:staff-symbol-line-thickness in staff-symbol-referencer-scheme,
   which simply gives you a Scheme interface to
       Staff_symbol_referencer::line_thickness (g)
-) Use this to shift inverted flags in the flags-in-scheme test case
   by the stem-width (the 'thickness grob property of the stem is given
   in units of the line-thickness!), so the flags really attach to the
   left edge of the stem
---
 input/regression/flags-in-scheme.ly    |  8 ++++++--
 lily/staff-symbol-referencer-scheme.cc | 10 ++++++++++
 scm/safe-lily.scm                      |  1 +
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/input/regression/flags-in-scheme.ly b/input/regression/flags-in-scheme.ly
index 5d9238a1ce..637f210866 100644
--- a/input/regression/flags-in-scheme.ly
+++ b/input/regression/flags-in-scheme.ly
@@ -23,10 +23,14 @@ testnotes = { \autoBeamOff c'8 d'16 c'32 d'64 \acciaccatura {c'8} d'64 c''8 d''1
 #(define (inverted-flag stem-grob)
   (let* ((dir (if (eqv? (ly:grob-property stem-grob 'direction) UP) "d" "u"))
          (flag (retrieve-glyph-flag "" dir "" stem-grob))
+         (line-thickness (ly:staff-symbol-line-thickness stem-grob))
+         (stem-thickness (ly:grob-property stem-grob 'thickness))
+         (stem-width (* line-thickness stem-thickness))
          (stroke-style (ly:grob-property stem-grob 'stroke-style))
          (stencil (if (null? stroke-style) flag
-                         (add-stroke-glyph flag stem-grob dir stroke-style ""))))
-    (ly:stencil-rotate-absolute stencil 180 0 0)))
+                         (add-stroke-glyph flag stem-grob dir stroke-style "")))
+         (rotated-flag (ly:stencil-rotate-absolute stencil 180 0 0)))
+    (ly:stencil-translate rotated-flag (cons (- (/ stem-width 2))  0))))
 
 {
   \override Score.RehearsalMark #'self-alignment-X = #LEFT
diff --git a/lily/staff-symbol-referencer-scheme.cc b/lily/staff-symbol-referencer-scheme.cc
index efa0fcd73d..d8f2e63862 100644
--- a/lily/staff-symbol-referencer-scheme.cc
+++ b/lily/staff-symbol-referencer-scheme.cc
@@ -37,3 +37,13 @@ LY_DEFINE (ly_position_on_line_p, "ly:position-on-line?",
   bool on_line = st ? Staff_symbol::on_line (g, pos) : false;
   return scm_from_bool (on_line);
 }
+
+LY_DEFINE (ly_staff_symbol_line_thickness, "ly:staff-symbol-line-thickness",
+           1, 0, 0, (SCM grob),
+           "Returns the line-thickness of the staff associated with @var{grob}.")
+{
+  LY_ASSERT_SMOB (Grob, grob, 1);
+  Grob *g = unsmob_grob (grob);
+  Real thickness = Staff_symbol_referencer::line_thickness (g);
+  return scm_from_double (thickness);
+}
diff --git a/scm/safe-lily.scm b/scm/safe-lily.scm
index ae3d56ccfb..5c79bba090 100644
--- a/scm/safe-lily.scm
+++ b/scm/safe-lily.scm
@@ -120,6 +120,7 @@
    ly:spanner-broken-into
    ly:spanner-bound
    ly:spanner?
+   ly:staff-symbol-line-thickness
    ly:stencil-add
    ly:stencil-aligned-to
    ly:stencil-combine-at-edge
-- 
2.39.2