[Webkit-unassigned] [Bug 264081] New: iPhone displays the image when alpha channel is 0 at runtime only, the screenshot is OK

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=264081

            Bug ID: 264081
           Summary: iPhone displays the image when alpha channel is 0 at
                    runtime only, the screenshot is OK
           Product: WebKit
           Version: Safari 17
          Hardware: iPhone / iPad
                OS: iOS 17
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebGL
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: scarletsky1025 at gmail.com
                CC: dino at apple.com, kbr at google.com, kkinnunen at apple.com

Created attachment 468453

  --> https://bugs.webkit.org/attachment.cgi?id=468453&action=review

it should be a white square, not includes firefox's logo.

## Description

This will happen when we try to draw a texture and set its alpha channel to 0 in the shader.

This is a very interesting bug.
It only occurs at runtime in high-end iPhone.
When we try to take a screenshot, the screenshot appears normal.

Here are my tested devices:

- MacBook Pro (M2 Pro, MacOS 13.3.1), runtime is OK.
- iPhone 8 (iOS 16.5), runtime is OK.
- iPhone XR (iOS 15.4), runtime is OK.
- iPhone SE2 (iOS 14.2), runtime is OK.
- iPhone 12 Pro Max (iOS 14.8.2), runtime is NOT OK.
- iPhone 12 Pro Max (iOS 16.1), runtime is NOT OK.
- iPhone 13 mini (iOS 17.1), runtime is NOT OK.
- iPhone 13 Pro Max (iOS 16.1), runtime is NOT OK.

## Reproduction steps

1. Open the https://codepen.io/scarletsky/full/oNmzNPz
2. You should see a white square, if you see firefox's logo, it is NOT OK.


I would like to know if there is any temporary workaround?

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