[nks (baumemo)]

Hi Felgo Team,

in our project we switched from felgo3 to felgo4 for the web (webassembly). This seems to work pretty good at the beginning but some (the exception rather than the rule) of our customers have problems with the version. They can’t use our application anymore. With the felgo3 version we had no such problems. We talked to them and we found the following Error in the developerconsole:

Uncaught TypeError: Cannot read properties of undefined                                       VM10:9

(reading ‘drawElementsInstanced’) at _emscripten_glDrawElementsInstancedARB

We have customers using latest Chrome and Edge (the version of the browser seems not to be the point) with this issue.

Any ideas how we can fix this problem?

[GüntherFelgo Team]

Hi,

thank you for reaching out!

We did not yet encounter this issue, so without actually reproducing the problem on a machine it will be hard to further investigate. If you can narrow down the problem to a certain code-part we can try to find a workaround.

But Felgo only extends Qt WebAssembly to support the SDK features. As the “drawElementsInstanced” error sounds related to the rendering I suspect some problem with the underlying Qt WebAssembly implementation and Emscripten toolchain. In case the error does also reproduce with a basic Qt Quick application, we can also submit a Qt bug report so Qt can investigate further and work on a fix.

Also, we plan to update the used Qt version from Qt 6.4 to the latest Qt 6.7 with the next Felgo SDK update. We plan to release it sometime later this year. It is possible that this update may already affect the problem and make WebAssembly more stable overall.

Best,
Günther

[nks (baumemo)]

Hi Günther,

it seems to be a problem while initialization or directly after initialization. Our code doesn’t make any special things. It seems like drawElementsInstanced is not set.

I have no chance to reproduce it on any machine I have. There are customers who have problems with latest edge or chrome but firefox works. It seems to be something system specific and a special edgecase. May be the given information is sufficient for a qt bug report?

If you like we can pre-test a Qt 6.7 webassembly build as soon a build is available from felgo?

Regards

[GüntherFelgo Team]

Adding a Qt bug report usually only makes sense if there’s a simple example, so they can investigate based on that. E.g. if you can provide the specific system/browser configuration where the crash always happens, ideally with a simple Qt Quick project without further dependencies. Otherwise it will be hard to reproduce and the bug won’t be investigated further.

We can let you know as soon as we have a testable version based on Qt 6.7. In the meantime, I would suggest that you recommend to use Firefox as a workaround for the rare cases where your customers report this issue.

[nks (baumemo)]

I will create a simple example and hope that one of our customers is that friendly testing it. Many customers are not allowed to use Firefox because of company restrictions.

Nevertheless the most promising solution is just get latest Qt linked.

Thank you so far! Looking forward to it :).