Bend_engraver: avoid mid-measure barlines

Defer setting the right bound of a BendAfter spanner until the end of
the timestep.  It is not known at the beginning of the timestep whether
a mid-measure barline will be created.

Update input/regression/bend-bound.ly to include barlines created with
\repeat and \bar.

Closes #6074.

(cherry picked from commit 32f3128)

input/regression/bend-bound.ly

@@ -1,23 +1,46 @@
 \version "2.17.30"
 
 \header {
-  texidoc = "Bends should not be effected by the full width of a
-@code{NonMusicalPaperColumn}. The bends should have identical X
-spans in the two examples.
+  texidoc = "Bends should not be affected by the full width of a
+@code{NonMusicalPaperColumn}.  The bends should have identical X
+spans in the two scores.  No bends should cross bar lines.
 "
 }
 
-music = \repeat unfold 16 { c''4\bendAfter #-4 }
-sixteens = \repeat unfold 64 { c'16 }
+music = \fixed c'' {
+  c4\bendAfter #-4
+  c4\bendAfter #-4
+  \repeat volta 2 {
+    c2\bendAfter #-4
+    |
+    c2\bendAfter #-4
+  }
+  c4\bendAfter #-4
+  c4\bendAfter #-4
+  |
+  c4\bendAfter #-4
+  c4\bendAfter #-4
+  \bar "||"
+  c2\bendAfter #-4
+  |
+  c2\bendAfter #-4
+  \bar "||"
+  c4\bendAfter #-4
+  c4\bendAfter #-4
+  |
+  \bar "|."
+}
+
+sixteenths = \repeat unfold 64 { c'16 }
 
 \new Score {
-  << \music \sixteens >>
+  << \music \sixteenths >>
 }
 
 \new Score \with {
   currentBarNumber = #200
   barNumberVisibility = #(every-nth-bar-number-visible 1)
   \override BarNumber.break-visibility = #end-of-line-invisible
 } {
-  << \music \sixteens >>
+  << \music \sixteenths >>
 }

lily/bend-engraver.cc

@@ -59,11 +59,6 @@ Bend_engraver::finalize ()
 void
 Bend_engraver::stop_fall ()
 {
-  bool bar = scm_is_string (get_property (this, "whichBar"));
-
-  fall_->set_bound (RIGHT, unsmob<Grob> (bar
-                                         ? get_property (this, "currentCommandColumn")
-                                         : get_property (this, "currentMusicalColumn")));
   last_fall_ = fall_;
   fall_ = 0;
   note_head_ = 0;
@@ -73,6 +68,18 @@ Bend_engraver::stop_fall ()
 void
 Bend_engraver::stop_translation_timestep ()
 {
+  if (last_fall_)
+    {
+      // don't cross a barline
+      SCM col_scm = scm_is_string (get_property (this, "whichBar"))
+        ? get_property (this, "currentCommandColumn")
+        : get_property (this, "currentMusicalColumn");
+      if (auto *col = unsmob<Grob> (col_scm))
+        {
+          last_fall_->set_bound (RIGHT, col);
+        }
+    }
+
   if (fall_ && !fall_->get_bound (LEFT))
     {
       fall_->set_bound (LEFT, note_head_);