Implements multiple-line non-cross-staff glissandi (issue4527086)

[mtsolo]

Reviewers: ,

Message:
I believe this new version of the glissando line breaking patch responds
to Keith's concern.

Please let me know what you think!

Cheers,
MS

Description:
Implements multiple-line non-cross-staff glissandi

Please review this at http://codereview.appspot.com/4527086/

Affected files:
  A input/regression/glissando-broken-multiple.ly
  M lily/line-spanner.cc
  M scm/define-grobs.scm
  M scm/output-lib.scm


Index: input/regression/glissando-broken-multiple.ly
diff --git a/input/regression/glissando-broken-multiple.ly  
b/input/regression/glissando-broken-multiple.ly
new file mode 100644
index  
0000000000000000000000000000000000000000..b9c8e20829e76ae603e82a77ea73bf5d0562cc35
--- /dev/null
+++ b/input/regression/glissando-broken-multiple.ly
@@ -0,0 +1,16 @@
+\header {
+  texidoc = "When broken, glissandi can span multiple lines."
+
+}
+\version "2.12.0"
+\paper {
+  ragged-right = ##T }
+
+\relative c'' {
+  \override Glissando #'breakable = ##t
+  d1 \glissando |
+  \break s1 |
+  \break s1 |
+  \break s1 |
+  c,1
+}
Index: lily/line-spanner.cc
diff --git a/lily/line-spanner.cc b/lily/line-spanner.cc
index  
0235243628b0dc1a74a9cab08c1d462b14a3bb42..76396705751893de94ea912d638a43544e71828d  
100644
--- a/lily/line-spanner.cc
+++ b/lily/line-spanner.cc
@@ -272,9 +272,14 @@ Line_spanner::print (SCM smob)
   while (flip (&d) != LEFT);

   Grob *my_common_y = common_y[LEFT]->common_refpoint (common_y[RIGHT],  
Y_AXIS);
-  do
-    span_points[d][Y_AXIS] += common_y[d]->relative_coordinate  
(my_common_y, Y_AXIS);
-  while (flip (&d) != LEFT);
+  bool simple_y = to_boolean (me->get_property ("simple-Y"))  
&& !to_boolean (me->get_property ("cross-staff"));
+
+  if (!simple_y)
+    {
+      do
+        span_points[d][Y_AXIS] += common_y[d]->relative_coordinate  
(my_common_y, Y_AXIS);
+      while (flip (&d) != LEFT);
+    }

   Interval normalized_endpoints = robust_scm2interval (me->get_property  
("normalized-endpoints"), Interval (0, 1));
   Real y_length = span_points[RIGHT][Y_AXIS] - span_points[LEFT][Y_AXIS];
@@ -341,7 +346,7 @@ Line_spanner::print (SCM smob)
     }

   line.translate (Offset (-me->relative_coordinate (commonx, X_AXIS),
-                         -me->relative_coordinate (my_common_y, Y_AXIS)));
+                         simple_y ? 0.0 : -me->relative_coordinate 
(my_common_y, Y_AXIS)));


   return line.smobbed_copy ();
Index: scm/define-grobs.scm
diff --git a/scm/define-grobs.scm b/scm/define-grobs.scm
index  
84c3f72f8fbb72c715ebab652bd81c2780b31998..d11a0e418afe10e4290d599e35f370f0bbb21c9e  
100644
--- a/scm/define-grobs.scm
+++ b/scm/define-grobs.scm
@@ -927,6 +927,7 @@
     (Glissando
      . (
        (after-line-breaking . ,ly:spanner::kill-zero-spanned-time)
+       (before-line-breaking . ,glissando::before-line-breaking)
        (bound-details . ((right . ((attach-dir .  ,CENTER)
                                    (padding . 1.5)
                                      ))
@@ -938,6 +939,7 @@
        (left-bound-info . ,ly:line-spanner::calc-left-bound-info)
        (normalized-endpoints . ,ly:spanner::calc-normalized-endpoints)
        (right-bound-info . ,ly:line-spanner::calc-right-bound-info)
+       (simple-Y . #t)
        (stencil . ,ly:line-spanner::print)
        (style . line)
        (X-extent . #f)
Index: scm/output-lib.scm
diff --git a/scm/output-lib.scm b/scm/output-lib.scm
index  
c25edf31f68a93de749a87e69e26cd4dde6dfc3d..d076b481a87ca57f618be4d9824a335093b6c0cd  
100644
--- a/scm/output-lib.scm
+++ b/scm/output-lib.scm
@@ -790,6 +790,31 @@ between the two text elements."


 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; glissando
+
+(define-public (glissando::before-line-breaking grob)
+  (let* ((l (glissando::internal-before-line-breaking grob LEFT))
+         (r (glissando::internal-before-line-breaking grob RIGHT))
+         (bd `((left . ,l) (right . ,r))))
+      (ly:grob-set-property! grob 'bound-details bd)))
+
+(define-public (glissando::internal-before-line-breaking grob dir)
+  (let* ((bound-details (ly:grob-property grob 'bound-details))
+         (dir-sym (if (eqv? dir LEFT) 'left 'right))
+         (other-sym (if (eqv? dir LEFT) 'right 'left))
+         (details (assoc-get dir-sym
+                             bound-details))
+         (other (assoc-get other-sym
+                           bound-details))
+         (extra-dy (assoc-get 'extra-dy details 0.0))
+         (bound (ly:spanner-bound grob dir))
+         (common-y (ly:grob-common-refpoint grob bound Y))
+         (y (+ (interval-center (ly:grob-extent bound common-y Y))
+               (/ (* dir extra-dy)
+                  2))))
+    (cons (cons 'Y y) details)))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; scripts

 (define-public (script-interface::calc-x-offset grob)