[WinUI3] Getting the real RasterizationScale in a custom control

[arivoir]

I'm writing a custom control that performs some drawing using a SpriteVisual and a DrawingSession. It works ok, but when it is inside a ScrollViewer it gets blurred as it is zoomed. How can I get the real rasterization scale, and get notified when it changes?

[AndrewKeepCoding]

Try the XamlRoot.Changed event. It will be fired when the rasterization scale is changed, or when the size is changed.

public sealed partial class CustomControl : Control
{
    public CustomControl()
    {
        DefaultStyleKey = typeof(CustomControl);
        Loaded += CustomControl_Loaded;
        Unloaded += CustomControl_Unloaded;
    }

    private void CustomControl_Loaded(object sender, RoutedEventArgs e)
    {
        this.XamlRoot?.Changed += CustomControl_XamlRootChanged;
    }

    private void CustomControl_Unloaded(object sender, RoutedEventArgs e)
    {
        this.XamlRoot?.Changed -= CustomControl_XamlRootChanged;
    }

    private void CustomControl_XamlRootChanged(XamlRoot sender, XamlRootChangedEventArgs args)
    {
        System.Diagnostics.Debug.WriteLine($"CustomControl XamlRoot changed. [Size: {sender.Size}, Scale: {sender.RasterizationScale}] ");
    }
}

[arivoir]

Hi @AndrewKeepCoding , Thank you very much for your feedback. I tried this approach, but the Changed event is not raised when the ScrollViewer is zoomed.

I'm using Microsoft.WindowsAppSDK Version="1.7.250606001".

[arivoir]

I created a sample that shows the drawings get blurred when ScrollViewer is zoomed.
WinUIRasterizationScaleInsideScrollViewer.zip

I also tried using composition api, so the drawing is updated when the rasterization scale changes, but I couldn't find any event for this purpose.