Bug 240975

Summary: Odd WebGL framebuffer issues on M1 macs
Product: WebKit Reporter: Evan Nowak <enowak>
Component: WebGLAssignee: Kenneth Russell <kbr>
Status: RESOLVED CONFIGURATION CHANGED    
Severity: Normal CC: ahmad.saleem792, dino, kbr, kkinnunen
Priority: P2    
Version: WebKit Nightly Build   
Hardware: Mac (Apple Silicon)   
OS: macOS 12   
Attachments:
Description Flags
Incorrect behavior
none
Correct behavior (from Intel Mac) none

Description Evan Nowak 2022-05-26 13:47:25 PDT 
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.
Comment 1 Evan Nowak 2022-05-26 13:48:27 PDT 
Created attachment 459792 [details]
Correct behavior (from Intel Mac)
Comment 2 Kenneth Russell 2022-05-26 15:47:35 PDT 
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.
Comment 3 Ahmad Saleem 2022-05-30 11:54:08 PDT 
I am unable to reproduce this bug as in the video using M1 Pro laptop with Safari 15.5 on macOS 12.4. Thanks!
Comment 4 Kenneth Russell 2022-05-31 11:04:55 PDT 
Thanks Ahmed. Evan, can you also confirm that this is working for you with Safari 15.5?
Comment 5 Evan Nowak 2022-05-31 11:28:25 PDT 
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!
Comment 6 Kenneth Russell 2022-05-31 18:11:20 PDT 
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.