[Webkit-unassigned] [Bug 192564] New: Regression (iOS 12): Keyboard dismissal leaves WKWebView viewport-fit=cover content offscreen

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=192564

            Bug ID: 192564
           Summary: Regression (iOS 12): Keyboard dismissal leaves
                    WKWebView viewport-fit=cover content offscreen
           Product: WebKit
           Version: Safari 12
          Hardware: iPhone / iPad
                OS: iOS 12
            Status: NEW
          Severity: Major
          Priority: P2
         Component: WebKit API
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: dvpdiner2 at gmail.com

Also filed as rdar://44655885

When an input that would require webview centering is clicked, the viewport is repositioned to center that input, as iOS has traditionally done. However, when dismissing the keyboard, the viewport is not re-positioned properly back to its original position.

A test project is available on GitHub: https://github.com/dpogue/WKScrollTest/tree/ios12-keyboard
Run the test project on a device or simulator. Tap the text input field to open the keyboard. Tap the Done button on the keyboard to dismiss it.


Expected Results:
The keyboard overlay closes and the web view is positioned as before: filling the screen.

Actual Results:
The keyboard overlay closes, but the web view does not return to its original position, leaving a space at the bottom of the screen. If rubberband bounce scrolling is disabled, it is not possible to return the web view to its intended position.


I strongly suspect this was introduced as a side effect of https://bugs.webkit.org/show_bug.cgi?id=187743 / https://trac.webkit.org/changeset/233905/webkit


This is impacting several popular frameworks that embed WKWebView:

- https://github.com/apache/cordova-ios/issues/417
- https://github.com/react-native-community/react-native-webview/issues/193
- https://github.com/ionic-team/capacitor/issues/814


Some additional comments from others:

 - when the viewport is in it's "stuck" position it seems as if any web elements still respond to interaction in their proper place. They are visually off the screen, but logically in the correct spot. This is similar to https://bugs.webkit.org/show_bug.cgi?id=158325

- webView.setNeedsLayout() on keyboard dismissal works as a workaround. UI is updated correctly but instantly, not smoothly like in Safari.


It sounds like the issue is essentially that the visible content area is not getting updated when the keyboard closes and the keyboard inset is removed.

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