Resetting a form with computed oneWay properties

Design
1

I’m modelling a form embeeded inside a modal and I’d like it to be reset when my route calls reset explicitly in the controller. This is somehow the form Im managing inside a modal:

{{#modal-window title='Size management' close='removeModal'}}
  <label>
    <span>Size</span>
    {{input value=width class='width'}}
    <span>X</span>
    {{input value=height class='height'}}
  </label>
  <label>
    <span>Left</span>
    {{input value=left class='left'}}
  </label>
  <label>
    <span>Top</span>
    {{input value=top class='top'}}
  </label>
{{/modal-window}}

This is the controller that presents/manages the form:

App.SizeEditorModalController = Ember.ObjectController.extend
  width: Ember.computed.oneWay 'model.width'
  height: Ember.computed.oneWay 'model.height'
  top: Ember.computed.oneWay 'model.top'
  left: Ember.computed.oneWay 'model.left'
 
  reset: ->
    # I'd like to restore the oneWay properties to its default values coming from the bound model

This is the route that shows the modal resetting previously the controller involved.

App.ApplicationRoute = Ember.Route.extend
  actions:
    showModal: (name, model)->
      controller = @controllerFor name
      controller.reset()
      @render name,
        into:   'application'
        outlet: 'modal'
        model:  model
    removeModal: ->
      @disconnectOutlet
        outlet:     'modal'
        parentView: 'application'

When I set some values to the form controls, they stay there forever, because I’m using oneWay properties and I don’t know if exists any way of resetting those properties to get the values from the source binding again. I don’t want the model to be updated before clicking ‘Save’ button. This is a quite common situation and I’m sure Ember has an easy way of achieving this, but, at the moment I cannot see what is this way.

Thanks in advance