Question about transparent widget background

Hi, I've seen some apps that can have the widget background truly transparent ( not screenshot, code-level transparent) How did they do that? Is that allowed to publish in App Store?

I would say post some screenshot examples of this.

I'm fairly sure it's not possible with the existing APIs and they get around it by having the same background photo that you use for your home screen.

Question about transparent widget background
 
 
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