How to align multiple children

[mpriem]

I've been working on a little bluetooth helper control and am not able to align child boxes. Could someone guide me on how to get the blue and green boxes to not take up the available space but instead stay a fixed size and the center box take up the available space?

I have tried different approaches with centerbox and box widgets but have not been able to get a good result yet.

Thanks in advance!

(defwindow bluetooth_ctl
  :monitor 0
  :windowtype "normal" 
  :wm-ignore true
  :geometry (geometry :x "-10px"
    :y "60px"
    :width "25%"
    :height "500px"
    :anchor "top right"
  )
  (bluetooth_ctl)
)

(defwidget bluetooth_ctl []
  (centerbox :class "pillbg bluetooth_ctl" :orientation "v" 
    (box :class "bluetooth_ctl_header" :height 30 
      (label :text "Bluetooth Devices" :yalign 0)
    )
    (box :orientation "v" :class "bluetooth_ctl_body"
      (for device in bluetooth_devices
        (box :orientation "h"
          (label :text "${substring(device,25,50)}" :xalign 0 :yalign 0)
          (button :onclick "bluetoothctl --timeout 5 connect ${substring(device,7,17)}" (label :text "Connect" :xalign 1 :yalign 0))
        )
      )
    )
    (box :class "bluetooth_ctl_footer"
      (button 
        :onclick "bluetoothctl --timeout 10 scan on"
        (label :text "Scan for devices" :yalign 1)
      )
    )
  )
)

[mpriem]

I have used the height widget attribute to set each element. It does result in properly sized elements but I was wondering if there are ways of achieving this dynamically?