[Webkit-unassigned] [Bug 238118] New: MSAA + disable depth_test causes depth invalid depth buffer

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=238118

            Bug ID: 238118
           Summary: MSAA + disable depth_test causes depth invalid depth
                    buffer
           Product: WebKit
           Version: Safari 15
          Hardware: Unspecified
                OS: macOS 10.15
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: ANGLE
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: brendanduncan at gmail.com
                CC: dino at apple.com, kbr at google.com, kkinnunen at apple.com

If I render into a multisampled framebuffer, clear the render target, draw with DEPTH_TEST disabled, and then draw with DEPTH_TEST enabled, the second draw call is rendered incorrectly.

Specifically, 
1) I create a color + depth render buffer with more than 1 MSAA sample, 
2) bind that framebuffer,
3) clear color + depth
4) disable DEPTH_TEST, depth mask
5) draw a quad
6) enable DEPTH_TEST, depth mask
7) draw a quad

The second quad is drawn incorrectly. If you set MSAA samples to 1, or if you don't disable DEPTH_TEST, the render is correct.

A test can be found here:
https://github.com/brendan-duncan/webgl_bug_tests/blob/main/msaa_depth_buffer.html
and viewed from here:
https://brendan-duncan.github.io/webgl_bug_tests/msaa_depth_buffer.html

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