[Webkit-unassigned] [Bug 206227] New: Fixed elements no longer stay fixed with elastic overscroll

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=206227

            Bug ID: 206227
           Summary: Fixed elements no longer stay fixed with elastic
                    overscroll
           Product: WebKit
           Version: Safari 13
          Hardware: Macintosh
                OS: macOS 10.15
            Status: NEW
          Severity: Major
          Priority: P2
         Component: Scrolling
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: cc.glows at gmail.com

Created attachment 387647

  --> https://bugs.webkit.org/attachment.cgi?id=387647&action=review

Demonstration of the minimal example

Minimal Example:

```html
<style>
  body {
    height: 2000px;
    margin: 0;
  }

  #fixed {
    position: fixed;
    top: 0;
    background: black;
    width: 100%;
    height: 100px;
  }
</style>

<div id="fixed"></div>
```

In earlier versions of macOS Safari (and current iOS Safari), the fixed header would stay fixed **including** the elastic overscroll. Now, it's not fixed when overscroll is in progress (like Chrome - which seems incorrect).

The problem here is that positioning libraries using `position: fixed` include window scroll to position elements, and Safari reports the overscroll included in the window.pageYOffset value, but since it's no longer fixed with it, the position is wrong when elastic scroll is in progress.

-- 
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-unassigned/attachments/20200114/a5de47f8/attachment-0001.htm>