Doc: CG - updates to lily-git section

[lilypond.git] / scm / output-lib.scm

diff --git a/scm/output-lib.scm b/scm/output-lib.scm
index 33ad81ae50405053fe015197c7a85fa40d32697b..0921cdd36f00b20d54442206d3a063ed2e9d0d05 100644 (file)
--- a/scm/output-lib.scm
+++ b/scm/output-lib.scm
@@ -902,8 +902,8 @@ and duration-log @var{log}."
     (set! rp (ly:make-stencil (ly:stencil-expr rp)
                               rp-x-extent
                               (ly:stencil-extent rp Y)))
-    (list (stencil-whiteout lp)
-          (stencil-whiteout rp))))
+    (list (stencil-whiteout-box lp)
+          (stencil-whiteout-box rp))))
 
 (define-public (parentheses-item::y-extent grob) (ly:grob::stencil-height grob))
 
@@ -967,14 +967,53 @@ and duration-log @var{log}."
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;
 
-(define-public (chain-grob-member-functions grob value . funcs)
-  (for-each
-   (lambda (func)
-     (set! value (func grob value)))
-   funcs)
-
-  value)
-
+(define-public (grob::compose-function func data)
+  "This creates a callback entity to be stored in a grob property,
+based on the grob property data @var{data} (which can be plain data, a
+callback itself, or an unpure-pure-container).
+
+Function or unpure-pure-container @var{func} accepts a grob and a
+value and returns another value.  Depending on the type of @var{data},
+@var{func} is used for building a grob callback or an
+unpure-pure-container."
+  (if (or (ly:unpure-pure-container? func)
+          (ly:unpure-pure-container? data))
+      (ly:make-unpure-pure-container
+       (lambda (grob) (ly:unpure-call func grob (ly:unpure-call data grob)))
+       (lambda (grob start end)
+         (ly:pure-call func grob start end
+                       (ly:pure-call data grob start end))))
+      (lambda (grob) (ly:unpure-call func grob (ly:unpure-call data grob)))))
+
+(define*-public (grob::offset-function func data
+                                       #:optional (plus +))
+  "This creates a callback entity to be stored in a grob property,
+based on the grob property data @var{data} (which can be plain data, a
+callback itself, or an unpure-pure-container).
+
+Function @var{func} accepts a grob and returns a value that is added
+to the value resulting from @var{data}.  Optional argument @var{plus}
+defaults to @code{+} but may be changed to allow for using a different
+underlying accumulation.
+
+If @var{data} is @code{#f} or @code{'()}, it is not included in the sum."
+  (cond ((or (not data) (null? data))
+         func)
+        ((or (ly:unpure-pure-container? func)
+             (ly:unpure-pure-container? data))
+         (ly:make-unpure-pure-container
+          (lambda rest
+            (plus (apply ly:unpure-call func rest)
+                  (apply ly:unpure-call data rest)))
+          (lambda rest
+            (plus (apply ly:pure-call func rest)
+                  (apply ly:pure-call data rest)))))
+        ((or (procedure? func)
+             (procedure? data))
+         (lambda rest
+           (plus (apply ly:unpure-call func rest)
+                 (apply ly:unpure-call data rest))))
+        (else (plus func data))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; falls/doits