+;; defined as a function instead of a list because the
+;; all-grob-descriptions alist is not available yet
+(define-public (find-named-props prop-name grob-descriptions)
+ "Used by @code{\\magnifyMusic} and @code{\\magnifyStaff}. When
+@var{grob-descriptions} is equal to the @code{all-grob-descriptions}
+alist (defined in @file{scm/define-grobs.scm}), this will find all grobs
+that can have a value for the @var{prop-name} property, and return them
+as a list in the following format:
+@example
+'((grob prop-name)
+ (grob prop-name)
+ ...)
+@end example"
+ (define (find-grobs-with-interface interface grob-descriptions)
+ (define (has-this-interface? grob-desc)
+ (let* ((meta (ly:assoc-get 'meta (cdr grob-desc)))
+ (interfaces (ly:assoc-get 'interfaces meta '())))
+ (memq interface interfaces)))
+ (let* ((grob-descriptions-with-this-interface
+ (filter has-this-interface? grob-descriptions))
+ (grob-names-with-this-interface
+ (map car grob-descriptions-with-this-interface)))
+ grob-names-with-this-interface))
+ (let* ((interface
+ (case prop-name
+ ((baseline-skip word-space) 'text-interface)
+ ((space-alist) 'break-aligned-interface)
+ (else (ly:programming-error
+ "find-named-props: no interface associated with ~s"
+ prop-name))))
+ (grobs-with-this-prop
+ (find-grobs-with-interface interface grob-descriptions)))
+ (map (lambda (x) (list x prop-name))
+ grobs-with-this-prop)))
+
+
+(define (magnifyStaff-is-set? context mag)
+ (let* ((Staff (ly:context-find context 'Staff))
+ (old-mag (ly:context-property Staff 'magnifyStaffValue)))
+ (not (null? old-mag))))
+
+(define (staff-magnification-is-changing? context mag)
+ (let* ((Staff (ly:context-find context 'Staff))
+ (old-mag (ly:context-property Staff 'magnifyStaffValue 1)))
+ (not (= old-mag mag))))
+
+(define-public (scale-fontSize func-name mag)
+ "Used by @code{\\magnifyMusic} and @code{\\magnifyStaff}. Look up the
+current @code{fontSize} in the appropriate context and scale it by the
+magnification factor @var{mag}. @var{func-name} is either
+@code{'magnifyMusic} or @code{'magnifyStaff}."