Karax question: how to update input field on the fly

[stedi]

Hope this is the right place for my question. I'm trying to update a text 
input. Having entered something in "input_1", I'd like to update the text 
that's shown in "input_2". With the code shown below, I'd expect "Auto text" to 
appear in input_2's text field. But that does not happen.
    
    
    include karax / prelude
    
    type
      Model = object
        value_1: string
        value_2: string
    
    var model: Model
    
    proc setInput(ev: Event, node:VNode): auto =
      model.value_1 = $node.text
      model.value_2 = "Auto text"
    
    proc createDom(): VNode =
      result = buildHtml(tdiv):
        input(id = "input_1", onchange=setInput)
        input(id = "input_2", value = model.value_2)
        input(id = "input_3", value = "Initial Value")
        p: text $model
    
    setRenderer createDom
    
    
    Run

I'd appreciate any kind of hint for solving my problem. Thanks a lot.