I noticed that some of my notebooks had recently (?) reverted to “code thumbnails”, rather than the glorious graphics they had some time earlier.
It used to be (google can attest to it)
In a more recent notebook such as https://observablehq.com/@fil/umap-a-personalized-distance-function, I’ve had to add a “static” mode in order to have a nice thumbnail — the worker version didn’t show up
This one seems to be back
However when I loaded the notebook here, a bunch of the cells were just red errors, which went away when I refreshed (I didn’t investigate the cause, sorry). So maybe something (e.g. external resource) failed to load when the thumbnail daemon tried to render it?
Puzzling! With an anonymous session the thumbnail is correct, but with my user @fil it’s incorrect. But there is no difference between the versions (i.e. the “Publish” button is not activated).
I believe this was due to the thumbnail process being slightly slow when loading and processing the notebook. If it still hasn’t rendered it all within a certain timeout, it’ll go ahead and look for canvas/svg/img’s and not find them and fallback to using a “code” version.
That being said, we just updated the process and I’ve anecdotally noticed it handling these cases better. So, I’m going to say this should be fixed now¹ and many more of your notebooks will gloriously thumbnail.
¹ Except those ones that for whatever reason intentionally take longer than 30s to render a graphic.