Only UIElement can be seen from UI Automation (like you have seen, OnCreateAutomationPeer starts from this class, not from the Visual class).

So you need to add UIElement (or derived like FrameworkElement) to the canvas, if you want it to be usable by UIAutomation.

You can create your own class like described here: Using DrawingVisual Objects or with a custom UserControl or use an existing one that suits your need but it must derive from UIElement somehow.

Once you have a good class, you can use the default AutomationPeer or override the method and adapt more closely.

If you want to keep Visual objects, one solution is to modify the containing object (but it still needs to derive from UIElement). For example, here if I follow the article in the link, I can write a custom containing object (instead of a canvas of your sample code so you may have to adapt slightly) like this:

public class MyVisualHost  : UIElement
{
    public MyVisualHost()
    {
        Children = new VisualCollection(this);
    }

    public VisualCollection Children { get; private set; }


    public void AddChild(Visual visual)
    {
        Children.Add(visual);
    }

    protected override int VisualChildrenCount
    {
        get { return Children.Count; }
    }

    protected override Visual GetVisualChild(int index)
    {
        return Children[index];
    }

    protected override AutomationPeer OnCreateAutomationPeer()
    {
        return new MyVisualHostPeer(this);
    }

    // create a custom AutomationPeer for the container
    private class MyVisualHostPeer : UIElementAutomationPeer
    {
        public MyVisualHostPeer(MyVisualHost owner)
            : base(owner)
        {
        }

        public new MyVisualHost Owner
        {
            get
            {
                return (MyVisualHost)base.Owner;
            }
        }

        // a listening client (like UISpy is requesting a list of children)
        protected override List<AutomationPeer> GetChildrenCore()
        {
            List<AutomationPeer> list = new List<AutomationPeer>();
            foreach (Visual visual in Owner.Children)
            {
                list.Add(new MyVisualPeer(visual));
            }
            return list;
        }
    }

    // create a custom AutomationPeer for the visuals
    private class MyVisualPeer : AutomationPeer
    {
        public MyVisualPeer(Visual visual)
        {
        }

        // here you'll need to implement the abstrat class the way you want
    }
}