[Webkit-unassigned] [Bug 211870] New: A portion of the WebGL canvas is not updated at all, after rotating the phone from the portrait mode to the landscape mode and then to the portrait mode again

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=211870

            Bug ID: 211870
           Summary: A portion of the WebGL canvas is not updated at all,
                    after rotating the phone from the portrait mode to the
                    landscape mode and then to the portrait mode again
           Product: WebKit
           Version: Safari 13
          Hardware: iPhone / iPad
                OS: iOS 13
            Status: NEW
          Severity: Major
          Priority: P2
         Component: WebGL
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: kei at superluffa.com
                CC: dino at apple.com

Created attachment 399315

  --> https://bugs.webkit.org/attachment.cgi?id=399315&action=review

The screen recording of the bug

Example URL:
https://newvr.s3.ap-northeast-2.amazonaws.com/vrshowroom/csa/csa0/lhdfull/index.html#sp2iexterior

Steps to reproduce the problem:
1. Open the url and wait to load the scene. Click the round button to open the webgl view.
2. Rotate the phone to the landscape mode so that the screen can rotate accordingly
3. Rotate the phone back to the portrait mode and see if the bottom part of the canvas is not updating. Repeat from #2, if this didn’t happen.
4. Now press the tab button of Chrome. Select the tab and see that the entire canvas is updating correctly.

What is the expected behavior?
The entire WebGL canvas should be updated no matter if a user has rotated the screen multiple times

What went wrong?
After quickly rotating a couple of times, some portion of the WebGL canvas is not updating at all. When I checked the canvas size, it occupies the entire screen. Also, as soon as I clicked the tab button to minimize the window for a while and came back to the same tab, the screen was updating normally.

Does it occur on multiple sites: Yes

Does this work in other browsers? Yes

Which browsers are affected? Safari 13 (iOS), Chrome 81.0.4044.124 (iOS)

OS Version: iOS 13.4.1

Another website with the same problem:
http://kiavr2017.s3-website.ap-northeast-2.amazonaws.com/handson/cn/cn1/#bdcexterior

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