Could you please provide a repro test along with the page under testing? Thanks.

The page with window.print(): 
http://www.galant-biz.ru/print.html


node.js code:
(async function() {
	
	const Koa = require('koa');
	const chrome = require('chrome-remote-interface');
	
	const app = new Koa();
	app.listen('9223');
	
	const target = await chrome.New();
	const client = await chrome({ target: target.id });
	const { DOM, Network, Page, Runtime } = client;
	await Promise.all([Page.enable(), Runtime.enable(), DOM.enable(), Network.enable()]);
	await Page.navigate({ url: 'http://www.galant-biz.ru/print.html' });
	setTimeout(async () => {
		console.log('timeout')
		await client.close();
		console.log('client closed')
		await chrome.Close(target);
	},10000)
	await Page.loadEventFired();
})();


Function loadEventFired() is never fired, client.close() is never finished.

It seems chrome://print dialog doesn't get open in HeadlessChrome.

You can check by calling GetWindowHandles() after navigating to 'http://www.galant-biz.ru/print.html' .

1) In normal Chrome, here is the output:

[24.948][INFO]: COMMAND GetWindows {
}
[24.948][DEBUG]: DevTools request: http://localhost:12506/json
[24.948][DEBUG]: DevTools response: [ {
   "description": "",
   "devtoolsFrontendUrl": "/devtools/inspector.html?ws=localhost:12506/devtools/page/65a1c866-629b-4085-9cc1-755c359dce29",
   "id": "65a1c866-629b-4085-9cc1-755c359dce29",
   "title": "Координаты «БЦ ГАЛАНТ» — версия для печати",
   "type": "other",
   "url": "chrome://print/",
   "webSocketDebuggerUrl": "ws://localhost:12506/devtools/page/65a1c866-629b-4085-9cc1-755c359dce29"
}, {
   "description": "",
   "devtoolsFrontendUrl": "/devtools/inspector.html?ws=localhost:12506/devtools/page/1b9150e9-e965-46df-b0f2-5c5d108d15a1",
   "id": "1b9150e9-e965-46df-b0f2-5c5d108d15a1",
   "title": "Chrome Automation Extension",
   "type": "background_page",
   "url": "chrome-extension://aapnijgdinlhnhlmodcfapnahmbfebeb/_generated_background_page.html",
   "webSocketDebuggerUrl": "ws://localhost:12506/devtools/page/1b9150e9-e965-46df-b0f2-5c5d108d15a1"
}, {
   "description": "",
   "id": "27f91d65-1118-47db-8431-451200a642ed",
   "title": "Координаты «БЦ ГАЛАНТ» — версия для печати",
   "type": "page",
   "url": "http://www.galant-biz.ru/print.html"
} ]
[24.948][INFO]: RESPONSE GetWindows [ "CDwindow-27f91d65-1118-47db-8431-451200a642ed", "CDwindow-65a1c866-629b-4085-9cc1-755c359dce29" ]



2) whereas, in Headless Chrome, the output is as follows:

[13.102][INFO]: COMMAND GetWindows {
}
[13.102][DEBUG]: DevTools request: http://127.0.0.1:9222/json
[13.102][DEBUG]: DevTools response: [ {
   "description": "",
   "id": "83577781-f7ad-4694-9006-03d31f141099",
   "title": "Координаты «БЦ ГАЛАНТ» — версия для печати",
   "type": "page",
   "url": "http://www.galant-biz.ru/print.html"
} ]

[13.102][INFO]: RESPONSE GetWindows [ "CDwindow-83577781-f7ad-4694-9006-03d31f141099" ]

Notice that "chrome://print/" is missing in output of HeadlessChrome.

Jianzhou: Is "chrome://print/" not supported on HeadlessChrome?

"chrome://print/" is not supported in headless chrome. The window.print() wouldn't open the printing dialog and the command is just ignored.
In headless chrome, the print settings are set via Page.printToPDF devtools command, instead of the printing dialog, which is a UI.

Maybe we can add the print to pdf feature into chromedriver so that users can print the page?

Oh, I just notice you are using chrome-remote-interface instead of chromedriver. So you can just use the Page.printToPDF command to print the page.

I will take a look at why loadEventFired is never fired.

Any update? 
The main question is actually why loadEventFired is never fired. I do not need to print this page, just want to ignore window.print() somehow. But it seems to hang the loadEventFired.

Anybody is working on this?

jzfeng@: Could you please provide an update to this issue? Thanks!

Any updates on Chrome Headless Driver's ability to support printToPDF via API ? 

Hi Eric, I think Jianzhou is no longer working on headless Chrome. Could you please take a look at this bug? Thanks.

Off to caseq@. Might also be a good starter bug for Johannes?

Sounds like the problem here is that the load event is not fired. Printing works as expected.

Moved issue chromedriver:1890 to now be issue chromium:834409.

Setting defect without priority to Pri-2.