Display nice error when reader doesn't support WebGL

[kelson42]

On my LibreWolf

Both Monaco and India

Here the log:

For the record, I have no prompt or error message appearing.

[rgaudin]

If you're using LibreWolf, you should know that (unless you change settings), you have to manually authorize each website to create WebGL contexts (because it's used for fingerprinting). Click on the icon on the address bar to do it.

[Jaifroid]

Monaco also doesn't work on Kiwix JS, though it may be a different issue. The test WebGL ZIM does work on KJS. See kiwix/kiwix-js#1434.
EDIT: This appears to have been a false alarm.

[kelson42]

If you're using LibreWolf, you should know that (unless you change settings), you have to manually authorize each website to create WebGL contexts (because it's used for fingerprinting). Click on the icon on the address bar to do it.

I will check again, but the root cause seems to be, indeed, lack of support in WebGL. Considering WebGL is not available in all recent browser, the ZIM should first test this properly and display a clear error message if not available. Something like for https://webglsamples.org/aquarium/aquarium.html

[benoit74]

See https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/By_example/Detect_WebGL

[rgaudin]

Considering WebGL is not available in all recent browser

That is misleading: “Since July 2015, this feature works across the latest devices and major browser versions”

That being said, as for other such technologies, we should have a graceful fallback (instead of a test).
For LibreWolf, it will fail the attempt/test. Would you want a message that says “check if you browser has an option that disabled it” or similar?

[benoit74]

For both this and #96 I propose to have same message:

This content requires {techno} to display properly, but it's currently unavailable in your setup.
**First, try updating:** Get the latest version of your browser or ZIM reader - newer versions usually fix this automatically.
**If you're using a browser:** Some browsers block {techno} typically for security reasons. You can either enable it in your browser settings, or try a different browser.

With {techno} being either WebGL, Fetch API or WebGL and Fetch API

WDYT, can you propose some enhancement?

[rgaudin]

I'd change security to privacy as that's more appropriate and less scary.