Get the size (after it has been “stretched”) of an item in a ViewBox

Question

Consider the following:

Let\'s say the Window is 1024x768 and the ViewBox fills the entire window, this means the TextBox is really large on th

Answer 1

This is how you get the ScaleTransform the ViewBox exerts on its children:

var child = VisualTreeHelper.GetChild(viewBox, 0) as ContainerVisual;
var scale = child.Transform as ScaleTransform;

Here viewBox is the ViewBox that textbox sits in. Then you can just multiply scale.ScaleX * textBox.ActualWidth and you get the size in Screen coordinates

But it gets even easier! To get that textbox's size directly in Screen Coordinates you do:

textbox.PointToScreen(new Point(textbox.ActualWidth,textbox.ActualHeight)) - textbox.PointToScreen(new Point(0,0))