(gobject:define-vtable ("GdkPaintable" paintable)
  (:skip parent-instance (:struct g:type-interface))
  ;; Methods of the GdkPaintable interface
  (snapshot (:void (paintable (g:object paintable))
                   (snapshot (g:object snapshot))
                   (width :double)
                   (height :double)))
  (get-current-image ((g:object paintable) (paintable (g:object paintable))))
  (get-flags (paintable-flags (paintable (g:object paintable))))
  (get-intrinsic-width (:int (paintable (g:object paintable))))
  (get-intrinsic-height (:int (paintable (g:object paintable))))
  (get-intrinsic-aspect-ratio (:double (paintable (g:object paintable)))))  

snapshot

Virtual function called by the gdk:paintable-snapshot function. You must implement the gdk:paintable-snapshot-impl method, when subclassing from the gdk:paintable interface.

get-current-image

Virtual function called by the gdk:paintable-current-image function. You must implement the gdk:paintable-get-current-image-impl method, when subclassing from the gdk:paintable interface.

get-flags

Virtual function called by the gdk:paintable-flags function. You must implement the gdk:paintable-get-flags-impl method, when subclassing from the gdk:paintable interface.

get-intrinsic-width

Virtual function called by the gdk:paintable-intrinsic-width function. You must implement the gdk:paintable-get-intrinsic-width-impl method, when subclassing from the gdk:paintable interface.

get-intrinsic-height

Virtual function called by the gdk:paintable-intrinsic-height function. You must implement the gdk:paintable-get-intrinsic-height-impl method, when subclassing from the gdk:paintable interface.

get-intrinsic-aspect-ratio-impl

Virtual function called by the gdk:paintable-intrinsic-aspect-ratio function. You must implement the gdk:paintable-get-intrinsic-aspect-ratio-impl method, when subclassing from the gdk:paintable interface.

;; Implementation of a NUCLEAR-ICON subclass
(gobject:define-gobject-subclass "NuclearIcon" nuclear-icon
  (:superclass g:object
   :export t
   :interfaces ("GdkPaintable"))
  ((rotation
    nuclear-icon-rotation
    "rotation" "gdouble" t t)))


;; This is the function that draws the actual icon
(defun nuclear-snapshot (snapshot foreground background width height rotation)
  (let ((size (min width height))
        (radius 0.3)
        (cr nil))
    (graphene:with-rects ((rect1 0 0 width height)
                          (rect2 (/ (- width size) 2.0)
                                 (/ (- height size) 2.0)
                                 size size))
      (gtk:snapshot-append-color snapshot background rect1)
      (setf cr (gtk:snapshot-append-cairo snapshot rect2))
      (cairo-set-source-rgba cr foreground)
      (cairo:translate cr (/ width 2.0) (/ height 2.0))
      (cairo:scale cr size size)
      (cairo:rotate cr rotation)
      (cairo:arc cr 0 0 0.1 (- pi) pi)
      (cairo:fill cr)
      (setf (cairo:line-width cr) radius)
      (setf (cairo:dash cr 0.0) (list (/ (* radius pi) 3)))
      (cairo:arc cr 0 0 radius (- pi) pi)
      (cairo:stroke cr)
      (cairo:destroy cr))))


;; Here, we implement the methods required by the GdkPaintable interface
(defmethod paintable-snapshot-impl
           ((paintable nuclear-icon) snapshot width height)
  (nuclear-snapshot snapshot
                    (rgba-new :red 0 :green 0 :blue 0 :alpha 1)
                    (rgba-new :red 0.9 :green 0.75 :blue 0.15 :alpha 1)
                    width
                    height
                    (nuclear-icon-rotation paintable)))


(defmethod paintable-get-flags-impl ((paintable nuclear-icon))
  (list :static-contents :static-size))