code: func (p *Panel) SetContent(w Widget) {
  	index := 0
  	if p.title != nil {
  		index++
  	}
  	if p.menu != nil {
  		index++
  	}
  	if p.content != nil {
  		p.RemoveWidget(p.content)
  	}
  	p.InsertWidget(index, w, 1.0)
  	p.content = w
  }
docs: // SetContent sets the Widget to display in the content area.