"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:

plotly.js/src/snapshot/filesaver.js

Lines 45 to 52 in 4529fe9

	if(canUseSaveLink) {
	saveLink.href = url;
	saveLink.download = name;
	document.body.appendChild(saveLink);
	saveLink.click();
	document.body.removeChild(saveLink);
	resolve(name);
	}

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

We should probably try using URL.createObjectURL.

---

Interestingly, we were using createObjectURL to some extent back before #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.

---

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 b31fef6

• 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

  plotly.js/devtools/test_dashboard/index.html

  Lines 22 to 24 in 3d383b7

  	<!-- uncomment below for IE9/10 support -->
  	<!-- <script>if(typeof window.Int16Array !== 'function')document.write("<scri"+"pt src='../../dist/extras/typedarray.min.js'></scr"+"ipt>");</script>
  	<script>document.write("<scri"+"pt src='../../dist/extras/request_animation_frame.js'></scr"+"ipt>");</script> -->

[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.