Failed to suspend the page with screen capture on

[sergiorussia]

Hi!
Steps to reproduce:

1. goto http://en.miui.com/forum.php
2. try to suspend the tab
3. the tab won't suspend, Console says "Uncaught DOMException: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported."

Reproducible: stable

[Firecul]

Sorry suspends fine for me.

[sergiorussia]

reproduced on both my machines.
here are few more details:

chrome console log:

contentscript.js:149 canvas: [object HTMLCanvasElement]
contentscript.js:150 Uncaught DOMException: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.
    at Object.onrendered (chrome-extension://klbibkeccnjlkjkiokjodocebajanakg/js/contentscript.js:150:46)
    at Object.o.complete (file:///home/sergio/.config/google-chrome/Default/Extensions/klbibkeccnjlkjkiokjodocebajanakg/6.30_0/js/html2canvas.min.js:8:2419)
    at o (file:///home/sergio/.config/google-chrome/Default/Extensions/klbibkeccnjlkjkiokjodocebajanakg/6.30_0/js/html2canvas.min.js:7:28352)
    at Image.e.onload (file:///home/sergio/.config/google-chrome/Default/Extensions/klbibkeccnjlkjkiokjodocebajanakg/6.30_0/js/html2canvas.min.js:7:29918)
onrendered @ contentscript.js:150
o.complete @ html2canvas.min.js:8
o @ html2canvas.min.js:7
e.onload @ html2canvas.min.js:7

Chrome 64, Ubuntu 16.04, adblockers were turned off for the test

[deanoemcke]

I have been able to reliably reproduce this.
It's important to note that it only occurs if the 'screen capturing' option is turned on.
It is an issue with the html2canvas library that I use. I have raised an issue on that project: niklasvh/html2canvas#1466

The current alpha build of TGS will not fail to suspend on this page, however, it will not be able to produce the screenshot and will just show a normal blank suspended tab page.

[deanoemcke]

People have suggested using https://github.com/tsayen/dom-to-image instead of html2canvas (as a solution to the above issue).
I will look into this as part of: #677

[deanoemcke]

I have added support for the dom-to-image screencapture library. Although it appears to be much slower, and also less reliable than html2canvas.
You can switch to the dom-to-image library by going to the extension debug.html page (chrome-extension:///debug.html) and toggling the "useAlternateScreenCaptureLib" option.

[sergiorussia]

nice, thanks, will check it out

[Pascal666]

Hopefully this change also fixes suspending https://9gag.com