anchor.diff:    (space-requirement+* (space-requirement+* (compose-label-space gadget)
                                               :min-width (* 2 (pane-x-spacing gadget))
                                               :width (* 2 (pane-x-spacing gadget))
  -                                            :max-width (* 2 (pane-x-spacing gadget))
  +                                            :max-width +fill+
                                               :min-height (* 2 (pane-y-spacing gadget))
                                               :height (* 2 (pane-y-spacing gadget))
  -                                            :max-height (* 2 (pane-y-spacing gadget)))
  +                                            :max-height +fill+
                          :min-width (* 2 *3d-border-thickness*)
                          :width (* 2 *3d-border-thickness*)
  -                       :max-width (* 2 *3d-border-thickness*)
                          :min-height (* 2 *3d-border-thickness*)
  -                       :height (* 2 *3d-border-thickness*)
  -                       :max-height (* 2 *3d-border-thickness*)))
  +                       :height (* 2 *3d-border-thickness*))))
   
   (defmethod handle-event ((pane push-button-pane) (event pointer-button-press-event))
     (with-slots (pressedp) pane
  
positive.code:            (ds (text-style-descent (pane-text-style gadget) gadget))
             (w  (+ (text-size gadget label :text-style (pane-text-style gadget)) wider))
             (h  (+ as ds higher)))
        (make-space-requirement :width w  :min-width w  :max-width  w
                                :height h :min-height h :max-height h))))
  
  (defgeneric draw-label* (pane x1 y1 x2 y2 &key ink))
  
  
negative.code:      (space-requirement+* sr
                            :min-width  (* 3 (pane-x-spacing pane))
                            :width      (* 3 (pane-x-spacing pane))
                            :max-width  +fill+
                            :min-height (* 2 (pane-y-spacing pane))
                            :height     (* 2 (pane-y-spacing pane))
                            :max-height +fill+)
       :min-width (space-requirement-height sr)
       :width     (space-requirement-height sr)
       :min-height 0
       :height 0)))
  
  (defgeneric draw-toggle-button-indicator (gadget type value x1 y1 x2 y2))
  