Bug 240975 – Odd WebGL framebuffer issues on M1 macs

• Component: WebGL
• Status: RESOLVED CONFIGURATION CHANGED

[Evan Nowak]

Created attachment 459791 [details]
Incorrect behavior

In Safari 15.4 on M1 macs we are seeing rendering issues in our web application, Onshape.  I verified this on a recent WebKit build (251013@main).

To reproduce the issue:
- Find an M1 Macbook (video was produced on a Macbook Air M1, 2020)
- Start up Safari 15.4
- Navigate to: https://cad.onshape.com/documents/ffedc1dc4bb9c3dc06004002/w/451e7b9d956f374a17b9118f/e/1ffdf0650483be1b8f5c255e
- Wait for page to load
- Move the mouse pointer over the cube that is visible in the WebGL canvas.  Note that the faces of the cube highlight as you move the pointer over them.
- Use the trackpad or scrollwheel to scroll while the mouse pointer is over the canvas.  This will cause the view to zoom in and out.  Alternatively, click in the canvas with the right mouse button and drag within the canvas.  This will cause the view to rotate.
- If these sorts of view manipulations are performed while a graphical highlight is visible, then the background shaded graphics will not update, however the highlight layer does display as expected.  (See "Incorrect behavior" video)

In other browsers and systems the background shaded graphics will update correctly as the view is manipulated.

I expect there is an issue at a fairly low level in either Safari's WebGL implementation, or in the display driver.  Highlights are achieved by rendering a subset of geometry in a highlight style to an off-screen framebuffer.  This is then composited on top of the main framebuffer for the WebGL context.  It looks as though something is going on with the framebuffer management.

[Evan Nowak]

Created attachment 459792 [details]
Correct behavior (from Intel Mac)

[Kenneth Russell]

Could you please take a system update and re-test on Safari 15.5? Many bugs in multisample resolution in ANGLE's Metal backend were fixed in this dot release, and on an M1 MacBook Pro running 15.5, these scenarios render correctly.

[Ahmad Saleem]

I am unable to reproduce this bug as in the video using M1 Pro laptop with Safari 15.5 on macOS 12.4. Thanks!

[Kenneth Russell]

Thanks Ahmed. Evan, can you also confirm that this is working for you with Safari 15.5?

[Evan Nowak]

Safari 15.5 is rendering correctly.

I found I had to manually update macOS because system preferences was showing it as up-to-date.  I am also not confident that the script to run the nightly build was working properly.

Anyways, thank you for pushing me in the right direction.  Sorry for the noise!

[Kenneth Russell]

No worries! Thanks for the report - we would rather hear about potential problems than not hear about real problems.

I'm not sure WebKit nightly builds are working, either, and the run-safari script in WebKit is definitely broken on M1 Macs (there's a bug filed here on bugs.webkit.org about that, but I can't look for it right now). The best bet is to test with Safari Technology Preview, or your own WebKit build via run-minibrowser.

Closing as WontFix - not reproducible.