--- /dev/null
+\version "2.16.0"
+
+\header {
+ lsrtags = "rhythms, tweaks-and-overrides"
+
+ texidoc = "
+The @code{stencil} property of the Flag grob can be set to a custom scheme
+function to generate the glyph for the flag.
+
+"
+ doctitle = "Generating custom flags"
+}
+
+#(define-public (weight-flag grob)
+ (let* ((stem-grob (ly:grob-parent grob X))
+ (log (- (ly:grob-property stem-grob 'duration-log) 2))
+ (is-up? (eqv? (ly:grob-property stem-grob 'direction) UP))
+ (yext (if is-up? (cons (* log -0.8) 0) (cons 0 (* log 0.8))))
+ (flag-stencil (make-filled-box-stencil '(-0.4 . 0.4) yext))
+ (stroke-style (ly:grob-property grob 'stroke-style))
+ (stroke-stencil (if (equal? stroke-style "grace")
+ (make-line-stencil 0.2 -0.9 -0.4 0.9 -0.4)
+ empty-stencil)))
+ (ly:stencil-add flag-stencil stroke-stencil)))
+
+
+% Create a flag stencil by looking up the glyph from the font
+#(define (inverted-flag grob)
+ (let* ((stem-grob (ly:grob-parent grob X))
+ (dir (if (eqv? (ly:grob-property stem-grob 'direction) UP) "d" "u"))
+ (flag (retrieve-glyph-flag "" dir "" grob))
+ (line-thickness (ly:staff-symbol-line-thickness grob))
+ (stem-thickness (ly:grob-property stem-grob 'thickness))
+ (stem-width (* line-thickness stem-thickness))
+ (stroke-style (ly:grob-property grob 'stroke-style))
+ (stencil (if (null? stroke-style)
+ flag
+ (add-stroke-glyph flag stem-grob dir stroke-style "")))
+ (rotated-flag (ly:stencil-rotate-absolute stencil 180 0 0)))
+ (ly:stencil-translate rotated-flag (cons (- (/ stem-width 2)) 0))))
+
+snippetexamplenotes = { \autoBeamOff c'8 d'16 c'32 d'64 \acciaccatura {c'8} d'64 }
+
+{
+ \override Score.RehearsalMark #'self-alignment-X = #LEFT
+ \time 1/4
+ \mark "Normal flags"
+ \snippetexamplenotes
+
+ \mark "Custom flag: inverted"
+ \override Flag #'stencil = #inverted-flag
+ \snippetexamplenotes
+
+ \mark "Custom flag: weight"
+ \override Flag #'stencil = #weight-flag
+ \snippetexamplenotes
+
+ \mark "Revert to normal"
+ \revert Flag #'stencil
+ \snippetexamplenotes
+}
+