Question

From within a C++/CX XAML application, how and when do I get information from the XAML layout engine to know where a particular control or grid position ended up, so that I can target my rendering to a SwapChainBackgroundPanel to specifically that area?

After immediately creating a page, and assigning it to the Current::Window->Content of the Application, I’m assuming I’ll need to wait for some sort of layout pass to call me back, etc.. Then, once that happens, where can I find the final layout positions (in Window-relative pixel coordinates) of grid positions, or any placeholder XAML element?

Answer 1

This should work once your descendant control raises the Loaded event (needs translation from C# to C++/CX):

Rect descendantControlBoundsInWindowCoordinateSpace = DescendantControl
    .TransformToVisual(Window.Current.Content)
    .TransformBounds(
        new Rect(
            0,
            0,
            DescendantControl.ActualWidth,
            DescendantControl.ActualHeight))