Function app_owned_content_window_rect 

pub fn app_owned_content_window_rect(
    content_rect: Rect,
    shadow: &Shadow,
    rim_width: f64,
) -> Rect

The native allocation around retained interactive content, including the shared floating silhouette, its rim and the themed elevation. Content geometry stays unchanged: the extra pixels are a transparent frame gutter, not padding inserted into the app’s layout or input coordinates.