Launched sim performance severely affected in Safari

[Nancy-Salpepi]

Test device
MacBook Air (m1 chip) and iMac Desktop

Operating System
12.4 and 10.15.7

Browser
Safari

Problem description
For phetsims/qa#816, when I launch the sim in studio, after checking a few checkboxes in the Model screen, the sim will basically come to a standstill and then sputter forward ~every second.

• This will only happen the first time the sim is launched. The issue won't repeat itself unless I clear my history
• Not seen with mac + chrome

Steps to reproduce

1. In studio, go to the Model screen
2. Press the Preview Sim button
3. In the launched sim, check the path and velocity checkboxes
4. Press Play button

Visuals

performance.mov

[samreid]

I tried on Macbook Air M1 with Safari Version 15.2 (17612.3.6.1.6). I emptied the cache and followed the instructions above, but the sim preview was a fast 60fps each time. I'm on MacOS 12.1. Same good behavior and local copy and on the dev version. @Nancy-Salpepi can you still replicate the problem? What safari versions are you using? Does it happen in the previous version or on phettest/master? We may need to collaborate to investigate this.

[Nancy-Salpepi]

@samreid I was able to reproduce this issue following the above steps in version 1.6, 1.5 and on master using 2 different macs:
MacBook Air m1 macOS 12.4 + safari Version 15.5 (17613.2.7.1.8)
iMac macOS 10.15.7 + safari Version 15.5 (15613.2.7.1.9)

Perhaps this has to do with the latest safari version?

[samreid]

Please see notes in phetsims/friction#278 (comment) about a potential flaw in safari 15.3 through 15.5. @Nancy-Salpepi can you please test this issue in 15.6?

[Nancy-Salpepi]

@samreid all looks good with Safari 15.6. I was unable to reproduce in 4 attempts.

[zepumph]

Excellent! I'm going to close this, @samreid please reopen if there are any other thoughts. Thanks all!