Plotly.js: "Failed - network error" when downloading large png using toImage button

[slishak]

I haven't yet found the actual limiting condition, but after some threshold of plot width/height/number of data points, I am unable to download a png of a Plotly plot. See following codepen:

https://codepen.io/anon/pen/WWZBOB

With n = 20000, I can't download the png, Chrome just shows the following message:

With n = 10000, it works. It also works with a 2000x2000 figure layout and 20000 points.

[etpinard]

Thanks for reporting!

Interestingly, downloading your graph in FF66 works fine. Chrome must put a URL-length limit in <a> with download attribute like we use here:

https://github.com/plotly/plotly.js/blob/4529fe92c6a13eb0ebeb4ede38592e67183d8df6/src/snapshot/filesaver.js#L45-L52

I found this stackoverflow post claiming that Chrome uses a 2MB limit.

We should probably try using URL.createObjectURL.

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Interestingly, we were using createObjectURL to some extent back before https://github.com/plotly/plotly.js/pull/446/

[etpinard]

PoC in https://github.com/plotly/plotly.js/compare/createObjectURL

We should be able to get a fix in the next minor 1.49.0 (I wouldn't want to try this our in a patch release).

[etpinard]

https://codepen.io/etpinard/pen/zVdjQg which uses https://42931-45646037-gh.circle-artifacts.com/0/dist/plotly.min.js

appears to work correctly on Chrome 70 and FF67 on my laptop.

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Before making a PR, we still need to test the legacy fallbacks on IE10, IE11 and Safari.

[antoinerg]

I manually tested saving mock 14.json to image by clicking the snapshot button in the modebar. I used a bundle built off your branch createObjectUrl which is currently at b31fef645f09248ebb194ce8efd6695b7d1d9b96

• [x] IE11: works
• [ ] Safari 12 on macOS Mojave: it goes to the following page instead of saving to file:
  
• [ ] IE10: cannot even render the figure even when uncommenting https://github.com/plotly/plotly.js/blob/3d383b796d5738b9f93356db2cc5b4b51570e4a5/devtools/test_dashboard/index.html#L22-L24

[etpinard]

Cool. Thanks! Have you tried downloading 14.json on Safari and IE10 off master?

[antoinerg]

Taking a snapshot of 14.json on Safari works off master: it downloads the image to the filesystem

[antoinerg]

In IE10 I can't load the dashboard and render anything.

[etpinard]

Things seems to now work ok in Safari off https://github.com/plotly/plotly.js/commit/ecf3ac7c739c2e1a4ae0a840c83cfd6c1731a2d2 on browserstack.

Still, before I make a PR, I would appreciate if someone with access to a Mac could test out https://codepen.io/etpinard/pen/QXraeW in Safari.

Thanks!