Compatibility issue with Safari 15

[mvaligursky]

Playcanvas engine fails to initialize on just released Safari 15. This seems to affect both Webgl1 and Webgl2 context.

This is the line that fails / makes the page reload:

engine/src/graphics/graphics-device.js

Line 301 in 6baccc6

gl = canvas.getContext(names[i], options);

When this line is commented out, the engine starts up:

engine/src/framework/application.js

Line 438 in 6baccc6

options.graphicsDeviceOptions.xrCompatible = true;

I don't see this problem mentioned online yet.

Looking at documentation:
https://www.w3.org/TR/webxr/

it's recommended makeXRCompatible() is suggested to be used instead of this flag for multiple reasons. It could trigger context loss which is possibly the reason we do not use it at the moment.

[willeastcott]

CC @Maksims

[mvaligursky]

This seems to have the same behaviour in Safari Technology Preview Release 132 (Safari 15.4, WebKit 16613.1.1.5)

[mvaligursky]

Some related discussions
immersive-web/webxr#1014
mrdoob/three.js#19275

[Maksims]

The use of makeXRCompatible can lead to context loss on multi-gpu systems.
One quickest option for action here: as Safari is misbehaving, then it should be a Safari-only fix not to affect all the other users.
As Safari does not support WebXR, we can safely not set the flag for Safari only. I understand this is not desired behaviour when we do platform-specific fixes, but this is a platform-specific bug with misbehaving from their side.

[mvaligursky]

This is the initial PR which added xrCompatible to options .. projects published before this are ok (Jan 2020)
#1834