[Webkit-unassigned] [Bug 271773] New: When the software keyboard is visible, simple webpages have visible and unavoidable overscroll

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=271773

            Bug ID: 271773
           Summary: When the software keyboard is visible, simple webpages
                    have visible and unavoidable overscroll
           Product: WebKit
           Version: Safari 17
          Hardware: iPhone / iPad
                OS: iOS 17
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: jarod.gowgiel at gmail.com
                CC: bfulgham at webkit.org, simon.fraser at apple.com,
                    zalan at apple.com

I have not yet figured out a way to prevent this, and the issue is IMO different enough from https://bugs.webkit.org/show_bug.cgi?id=191204 that I wanted to file a separate issue.

On iOS Safari, focusing a text input causes the viewport to scroll without changing the height of the window. This has been sufficiently complained about in https://bugs.webkit.org/show_bug.cgi?id=141832 and https://bugs.webkit.org/show_bug.cgi?id=191204, so I won't focus on that here. The specific bug I'm reporting is that, when the viewport has scrolled up, it is possible to overscroll the window substantially regardless of the CSS rules that are set on the `html` or `body`. Steps to reproduce:

1. Open https://codepen.io/JarodG/pen/eYoEYdo
2. Scroll to the very bottom of the window
3. Notice: without text focused, the bottom of the editor (containing some CodePen UI) is the bottom of the scrollable window.
4. Now, tap into the text box
5. Scroll to the bottom of the window
6. Notice: with text focused, it is possible to further scroll past the bottom edge of the page. This leaves a huge empty space that is not actually a part of the DOM, as best I can tell.

For full window single page applications, this presents an immediate problem. As soon as there is any text focused on the entire screen, it is possible to overscroll away from the normal bounds of the window and into this empty, uncontrollable space. The desired behavior, IMO, would be for some combination of CSS properties or meta viewport tags to instead limit scrolling at least to the actual bounds of the HTML.

It would also be great if it were possible to calculate in the height of the software keyboard using some kind of unit or property, but based on the discussion in https://bugs.webkit.org/show_bug.cgi?id=141832 it seems that is not something the WebKit team will consider.

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