<w-slider v-model="paneSize" label="First pane size" :min="0" :max="100">

<splitpanes class="default-theme" @resize="paneSize = $event[0].size" style="height: 400px">

  <pane :size="paneSize">

    <span>{{ paneSize }}%</span>

  </pane>

  <pane :size="100 - paneSize">

    <span>{{ 100 - paneSize }}%</span>

  </pane>

     <span>{{ 100 - paneSize }}%</span>

</splitpanes>