External URIs

[richardmarcus]

• We also want to access non MMT graphs, but...
  Access to XMLHttpRequest at 'https://kwarc.info/teaching/IWGS/graph.json' from origin 'https://tgview3d.mathhub.info' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
  cc: @tkw1536

[kohlhase]

I think this is something related to https://medium.com/@dtkatz/3-ways-to-fix-the-cors-error-and-how-access-control-allow-origin-works-d97d55946d9
We could fix it at the level of MathHub but that would not help TGView itself.

[richardmarcus]

the second solution with https://cors-anywhere.herokuapp.com/ as proxy seems to work fine, but not sure if we want to rely on this in the future

[kohlhase]

Well maybe this is something for standalone TGView. In MathHub we already have a proxy we could (better) use (maybe extend for this). This is closer to solution 3.
@richardmarcus why don't you implement solution2 for tgview3D standalone and @tkw1536 can think about the MathHub integration.

[richardmarcus]

Standalone TGView is not affected because CORS only affects browser-server communication.
Until we have something better, I integrated the mentioned proxy.
https://tgview3d.mathhub.info/?kwarc.info/teaching/IWGS/graph.json now automatically loads the IWGS graph