* scm/define-grobs.scm (all-grob-descriptions): make NonMusicalPaperColumn

	page-breakable by default

	* scm/layout-page-layout.scm (space-systems): fix bug where the force isn't
	correctly calculated for a single-system page

	* scm/lily-library.scm (interval-sane?): check that the first number is no
	bigger than the second number

	* lily/simple-spacer.cc (solve): allow compression even when ragged (but we
	acknowledge that we aren't satisfying constraints)

	* lily/hara-kiri-group-spanner.cc (request_suicide): give equal treatment to
	non-Items

	* lily/grob.cc (pure_height): add minimum-Y-extent

	* lily/gourlay-breaking.cc (solve): don't ignore a compression force, even if we're
	ragged

	* lily/constrained-breaking.cc: convert code to use new Matrix class
	(get_best_solution): new function

	* scm/page.scm (make-page-stencil): don't crash if we annotate-layout when there
	is a page with no systems

4 files changed, 16 insertions, 9 deletions

diff --git a/scm/define-grobs.scm b/scm/define-grobs.scm
index a8e3c092c4..b0d023b2be 100644
--- a/scm/define-grobs.scm
+++ b/scm/define-grobs.scm
@@ -1140,6 +1140,7 @@
 	
 	(non-musical . #t)
 	(line-break-permission . allow)
+	(page-break-permission . allow)
 
 	;; debugging stuff: print column number.
 	;;		 (font-size . -6) (font-name . "sans")	(Y-extent . #f)
diff --git a/scm/layout-page-layout.scm b/scm/layout-page-layout.scm
index f00fbf1ca0..8756062384 100644
--- a/scm/layout-page-layout.scm
+++ b/scm/layout-page-layout.scm
@@ -127,18 +127,24 @@ is what have collected so far, and has ascending page numbers."
 (define (space-systems page-height lines ragged? paper)
   "Compute lines positions on page: return force and line positions as a pair.
  force is #f if lines do not fit on page."
-  (let* ((springs (map (lambda (prev-line line)
+  (let* ((empty-stencil (ly:make-stencil '() '(0 . 0) '(0 . 0)))
+	 (empty-prob (ly:make-prob 'paper-system (list `(stencil . ,empty-stencil))))
+	 (cdr-lines (append (cdr lines)
+			    (if (<= (length lines) 1)
+				(list empty-prob)
+				'())))
+	 (springs (map (lambda (prev-line line)
                          (list (line-ideal-distance prev-line line paper)
                                (/ 1.0 (line-next-space prev-line line paper))))
                        lines
-                       (cdr lines)))
+                       cdr-lines))
          (rods (map (let ((i -1))
                       (lambda (prev-line line)
                         (set! i (1+ i))
                         (list i (1+ i)
                               (line-minimum-distance prev-line line paper))))
                        lines
-                       (cdr lines)))
+                       cdr-lines))
          (last-line (car (last-pair lines)))
          (topskip (first-line-position (first lines) paper))
          (space-to-fill (- page-height
diff --git a/scm/lily-library.scm b/scm/lily-library.scm
index d178c6926c..bb7e7a32a8 100644
--- a/scm/lily-library.scm
+++ b/scm/lily-library.scm
@@ -383,7 +383,8 @@ found."
   (not (or  (nan? (car i))
 	    (inf? (car i))
 	    (nan? (cdr i))
-	    (inf? (cdr i)))))
+	    (inf? (cdr i))
+	    (> (car i) (cdr i)))))
 
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
diff --git a/scm/page.scm b/scm/page.scm
index a572e44102..258589ae53 100644
--- a/scm/page.scm
+++ b/scm/page.scm
@@ -314,8 +314,10 @@ create offsets.
        (foot (prop 'foot-stencil))
        )
 
-    (if (or (annotate? layout)
-	    (ly:output-def-lookup layout 'annotate-systems #f))
+    (if (and
+	 (or (annotate? layout)
+	     (ly:output-def-lookup layout 'annotate-systems #f))
+	 (pair? lines))
 
 	(begin
 	  (for-each (lambda (sys next-sys)
@@ -386,9 +388,6 @@ create offsets.
   (let*
       ((p-book (page-property page 'paper-book))
        (layout (ly:paper-book-paper p-book))
-       (scopes (ly:paper-book-scopes p-book))
-       (number (page-page-number page))
-       (last? (page-property page 'is-last))
        (h (- (ly:output-def-lookup layout 'paper-height)
 	       (ly:output-def-lookup layout 'top-margin)
 	       (ly:output-def-lookup layout 'bottom-margin)))