Can I use wry for transparent overlay for native window?

[Goldenbough44]

My goal is to draw a translucent web view on the Vulkan render. In the transparent part of the web view, the Vulcan rendered result behind the webview should be shown.

I use SDL window, and use Vulkan for rendering. I tried to use wry webviewbuilder with_transparent(true), and html background color is transparent, but the web view is rendered while covering the vulkan rendering in black.

Doesn't wry support transparency when drawing build_as_child on the native window?
Or did there be a problem in the process of combining with Vulkan?
Or is it because of compatibility issues with SDL?