+
+(define pure-print-callbacks
+ (list
+ `(,ly:note-head::print . '())
+ `(,ly:clef::print . '())
+ `(,ly:text-interface::print . '())
+ `(,ly:script-interface::print . '())))
+
+;; ly:grob::stencil-extent is safe iff the print callback is safe too
+(define (pure-stencil-height grob start stop)
+ (let ((sten (ly:grob-property-data grob 'stencil)))
+ (if (or
+ (ly:stencil? sten)
+ (pair? (assq sten pure-print-callbacks)))
+ (ly:grob::stencil-height grob)
+ '(0 . 0))))
+
+(define pure-Y-extents
+ (list
+ `(,ly:staff-symbol::height . ())))
+
+(define Y-extent-conversions
+ (list
+ `(,ly:stem::height . ,ly:stem::pure-height)
+ `(,ly:grob::stencil-height . ,pure-stencil-height)
+ `(,ly:side-position-interface::y-aligned-side . ,ly:side-position-interface::pure-y-aligned-side)
+ `(,ly:axis-group-interface::height . ,ly:axis-group-interface::pure-height)
+ `(,ly:hara-kiri-group-spanner::y-extent . ,ly:hara-kiri-group-spanner::pure-height)
+ `(,ly:slur::height . ,ly:slur::pure-height)))
+
+(define pure-Y-offsets
+ (list
+ `(,ly:staff-symbol-referencer::callback . ())))
+
+(define Y-offset-conversions
+ (list
+ `(,ly:side-position-interface::y-aligned-side . ,ly:side-position-interface::pure-y-aligned-side)))
+
+(define-public (pure-relevant grob)
+ (let ((extent-callback (ly:grob-property-data grob 'Y-extent)))
+ (or
+ (pair? extent-callback)
+ (pair? (assq extent-callback pure-Y-extents))
+ (and
+ (pair? (assq extent-callback Y-extent-conversions))
+ (or
+ (not (eq? extent-callback ly:grob::stencil-height))
+ (pair? (assq (ly:grob-property-data grob 'stencil) pure-print-callbacks))
+ (ly:stencil? (ly:grob-property-data grob 'stencil)))))))
+
+(define (pure-conversion pures conversions defsymbol defreturn rettype? grob start stop)
+ (let* ((normal-callback (ly:grob-property-data grob defsymbol))
+ (pure-callback (assq normal-callback conversions)))
+ (if (rettype? normal-callback)
+ normal-callback
+ (if (pair? (assq normal-callback pures))
+ (normal-callback grob)
+ (if (pair? pure-callback)
+ ((cdr pure-callback) grob start stop)
+ defreturn)))))
+
+(define-public (pure-Y-extent grob start stop)
+ (pure-conversion pure-Y-extents Y-extent-conversions
+ 'Y-extent '(0 . 0) pair? grob start stop))
+
+(define-public (pure-Y-offset grob start stop)
+ (pure-conversion pure-Y-offsets Y-offset-conversions
+ 'Y-offset 0 number? grob start stop))