Viewport Origin animation

Question

I am developing a Windows phone app, where I have a viewportcontroller, that enables me to zoom in and out on content. I want to center the zoom at the point where I zoom. Whic

Answer 1

I have no experience with the ViewportControl, and I am assuming ViewportControl.SetViewportOrigin() is the only way to set the origin (i.e. : there are no properties to do it).

If that's the case, you could wrap the ViewportControl in a custom control.

Add two dependency properties that control (ViewportX and ViewportY, or one dependency property of type Point), and in the storyboard, animate those two properties (with a simple DoubleAnimation).

In the value changed callbacks of those properties, you can then call SetViewportOrigin() with the changed values.

so something like:

public class WrappedViewport : Control
{
    private ViewportControl _viewportControl;
    protected override OnApplyTemplate()
    {
        // make sure there is an appropriate default style in generic.xaml
        _viewportControl = (ViewportControl)GetTemplateChild("Viewport"); 
    }

    #region ViewportX
    private static void ViewportXChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        WrappedViewport owner = (WrappedViewport)d;
        owner._viewportControl.SetViewportOrigin(ViewportX, ViewportY);
    }

    private static readonly DependencyProperty ViewportXProperty = DependencyProperty.Register("ViewportX",
                                                                                          typeof(double),
                                                                                          typeof(WrappedViewport),
                                                                                          new PropertyMetadata(0d, ViewportXChangedCallback));

    public double ViewportX
    {
        get { return (double)GetValue(ViewportXProperty ); }
        set { SetValue(ViewportXProperty , value); }
    }
    #endregion

    #region ViewportY
    private static void ViewportYChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        WrappedViewport owner = (WrappedViewport)d;
        owner._viewportControl.SetViewportOrigin(ViewportX, ViewportY);
    }

    private static readonly DependencyProperty ViewportYProperty = DependencyProperty.Register("ViewportY",
                                                                                          typeof(double),
                                                                                          typeof(WrappedViewport),
                                                                                          new PropertyMetadata(0d, ViewportYChangedCallback));

    public double ViewportY
    {
        get { return (double)GetValue(ViewportYProperty ); }
        set { SetValue(ViewportYProperty , value); }
    }
    #endregion
}

See also http://msdn.microsoft.com/en-us/library/ms752914(v=vs.110).aspx