i made a simple xcode project that loads my webapp using UIWebview
the problem is the top and the bottom of the app is white in both iphone x/xs/xr and ipad pro
As far as I know, that depends on the correct usage of splash screen configuration. If you have some images with wrong dimensions, it renders the app in a sort of fall-back layout.
Yes, I think that could make the difference. The Framework7 CLI can automatically create and configure the splash screens automatically. Or if you have already setup your project, you can lookup the correct dimensions in xcode image asset catalog placeholders.