How do I display it from a designated point in WebView of Swift?

I think there are two ways.
One way is to fix the display position and make the upper part invisible from the red line. I didn't understand this.

The second way is to erase the top part from the red line.

I think you can run javascript from the swift side, manipulate html, and rewrite the source code on the page.

However, I think this will require a little knowledge of html and javascript.