Question

Is there a way to bind to the mouse position in WPF in the XAML file? Or does that have to be done in code? I have a control inside a Canvas, and I just want the control to follow the mouse while the mouse cursor is inside the Canvas.

Thanks

---

EDIT:

OK, I figured it out a relatively easy way using the code-behind file. I added a MouseMove event handler on the Canvas, and then added:

    private void Canvas_MouseMove(object sender, MouseEventArgs e)
    {
        // Get the x and y coordinates of the mouse pointer.
        System.Windows.Point position = e.GetPosition(this);
        double pX = position.X;
        double pY = position.Y;

        // Sets the position of the image to the mouse coordinates.
        myMouseImage.SetValue(Canvas.LeftProperty, pX);
        myMouseImage.SetValue(Canvas.TopProperty, pY);
    }

using http://msdn.microsoft.com/en-us/library/ms746626.aspx as a guideline.

Answer 1

I tried to make a kind of decorator for this purpose.
You wrap the object, mouse position above which you want to control and bind some control to decorator MousePosition property.

public class MouseTrackerDecorator : Decorator
{
    static readonly DependencyProperty MousePositionProperty;
    static MouseTrackerDecorator()
    {
        MousePositionProperty = DependencyProperty.Register("MousePosition", typeof(Point), typeof(MouseTrackerDecorator));
    }

    public override UIElement Child
    {
        get
        {
            return base.Child;
        }
        set
        {
            if (base.Child != null)
                base.Child.MouseMove -= _controlledObject_MouseMove;
            base.Child = value;
            base.Child.MouseMove += _controlledObject_MouseMove;
        }
    }

    public Point MousePosition
    {
        get
        {
            return (Point)GetValue(MouseTrackerDecorator.MousePositionProperty);
        }
        set
        {
            SetValue(MouseTrackerDecorator.MousePositionProperty, value);
        }
    }

    void _controlledObject_MouseMove(object sender, MouseEventArgs e)
    {
        Point p = e.GetPosition(base.Child);

        // Here you can add some validation logic
        MousePosition = p;            
    }
}

and XAML

<local:MouseTrackerDecorator x:Name="mouseTracker">
    <Canvas Width="200" Height="200" Background="Red">
        <Button Width="20" Height="20" Canvas.Left="{Binding ElementName=mouseTracker, Path=MousePosition.X}" Canvas.Top="{Binding ElementName=mouseTracker, Path=MousePosition.Y}"  />
    </Canvas>
</local:MouseTrackerDecorator>