Discuss requirement of cross-origin isolated

[maxammann]

maplibre-rs currently requires that the host site, which runs maplibre-rs needs to be "corss-origin isolated". This is a quite strict requirement: https://web.dev/coop-coep/

The reason for this requirement is the usage of SharedArrayBuffer. I see three possible solutions for this problem:

• Provide an alternative implementation for "multi-threading" on the web. This would complicate the asynchronous capabilities of maplibre-rs even more. This also introduces a performance penalty because computed data needs to be serialized in order to pass it between WebWorkers
• Hope that the restrictions for SharedArrayBuffer are lowered in the next 2 years.
• Live with that fact. This is probably not really possible. Enabling "cross-origin isolation" has an impact on any cross-origin resources used by users.

More Info: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer/Planned_changes

[maxammann]

There are apparently discussions about removing the restrictions for SharedArrayBuffer:

May 6, 2021: Based on feedback and issues reported we've decided to adjust the timeline for SharedArrayBuffer usage in none cross-origin isolated sites to be restricted in Chrome M92.

https://web.dev/coop-coep/

[maxammann]

Minor relaxation: https://github.com/WICG/credentiallessness

[maxammann]

related: whatwg/html#6364

[maxammann]

moved to: #60