+(define (partial-ellipse x-radius y-radius start-angle end-angle thick connect fill)
+ (define (make-ellipse-radius x-radius y-radius angle)
+ (/ (* x-radius y-radius)
+ (sqrt (+ (* (* y-radius y-radius)
+ (* (cos angle) (cos angle)))
+ (* (* x-radius x-radius)
+ (* (sin angle) (sin angle)))))))
+ (let*
+ ((new-start-angle (* PI-OVER-180 (angle-0-360 start-angle)))
+ (start-radius (make-ellipse-radius x-radius y-radius new-start-angle))
+ (new-end-angle (* PI-OVER-180 (angle-0-360 end-angle)))
+ (end-radius (make-ellipse-radius x-radius y-radius new-end-angle))
+ (epsilon 1.5e-3)
+ (x-end (- (* end-radius (cos new-end-angle))
+ (* start-radius (cos new-start-angle))))
+ (y-end (- (* end-radius (sin new-end-angle))
+ (* start-radius (sin new-start-angle)))))
+ (if (and (< (abs x-end) epsilon) (< (abs y-end) epsilon))
+ (entity
+ 'ellipse ""
+ `(fill . ,(if fill "currentColor" "none"))
+ `(stroke . "currentColor")
+ `(stroke-width . ,thick)
+ '(stroke-linejoin . "round")
+ '(stroke-linecap . "round")
+ '(cx . 0)
+ '(cy . 0)
+ `(rx . ,x-radius)
+ `(ry . ,y-radius))
+ (entity
+ 'path ""
+ `(fill . ,(if fill "currentColor" "none"))
+ `(stroke . "currentColor")
+ `(stroke-width . ,thick)
+ '(stroke-linejoin . "round")
+ '(stroke-linecap . "round")
+ (cons
+ 'd
+ (string-append
+ (ly:format
+ "M~4f ~4fA~4f ~4f 0 ~4f 0 ~4f ~4f"
+ (* start-radius (cos new-start-angle))
+ (- (* start-radius (sin new-start-angle)))
+ x-radius
+ y-radius
+ (if (> 0 (- new-start-angle new-end-angle)) 0 1)
+ (* end-radius (cos new-end-angle))
+ (- (* end-radius (sin new-end-angle))))
+ (if connect
+ (ly:format "L~4f,~4f"
+ (* start-radius (cos new-start-angle))
+ (- (* start-radius (sin new-start-angle))))
+ "")))))))
+