Thank you shinn.ko...@gmail.com for re-opening this issue. I would be overjoyed to see it get fixed! To demonstrate my commitment to this goal, I have taken it upon myself to spend the past several hours thoroughly researching & documenting the issue. Here is what I have found:

1. The issue does not appear to be specific to Google Hangouts. It seems to happen every time an app/extension/website calls the chrome.desktopCapture API (https://developer.chrome.com/extensions/desktopCapture), on a multi-monitor Linux machine.
2. It seams that there have been other discussions about this same issue on other forums, of which none seem to be resolved. For example, Jarryd over at Unix Stack Exchange responded to a similar question by explaining “I don't know how you get a single monitor, I have never seen that. But as for both monitors at the same time, I suspect that Chromium only shares an X "screen". XRandR makes both monitors appear on one X screen, so until someone at Google fixes that I doubt there is a workaround ...” That post is located at http://unix.stackexchange.com/questions/152435/sharing-your-desktop-with-google-hangouts-dual-monitor-and-gnome-shell Furthermore, there is also this forum which seems to be about this same issue: https://productforums.google.com/forum/#!topic/hangouts/3-tgrHYPXlA
2. There are other applications that run on Linux in which can capture an individual screen. A good example of this would be VokoScreen (https://github.com/vkohaupt/vokoscreen). In Ubuntu it can be installed via sudo apt-get install vokoscreen. Thus, I know that it is technically possible to capture an individual screen on Linux. Having such an example program to investigate might be helpful if/when someone attempts to fix this issue.

I have also done some experimentation in VirtualBox to further investigate and document the issue. Here is what I have done:

For the purposes of testing and experimentation I installed a fresh copy of Windows 7 Ultimate, along side a fresh copy of Ubuntu 16.04. I gave each machine 2 monitors in the VirtualBox settings, and configured the applicable monitor settings within each operating system so that each correctly recognized both monitors. From there, I installed the latest version of Chrome, (54.0.2840.71), and signed into it. I also changed the background on each operating system to an identical image for comparison, and so that each screen could be identified. From there, I attempted to use the screen-sharing functionality in 4 different apps/sites on each system so that the results could be compared. Here are the apps/sites that I tried:

1. Google Hangouts, (https://hangouts.google.com/), I started a VIDEO CALL and hit menu > Share screen to share my screen.
2. https://appear.in/, I typed some text into the box, clicked start, and when it connected, attempted to screen share. (Note: an extension was required in order for this to work).
3. https://meet.jit.si/ This service is similar to appear.in, so I proceeded in a similar manner to the above steps for appear.in. An extension was also required to allow screen sharing in this site.
4. The Desktop Capture Sample chrome app found at: https://chrome.google.com/webstore/detail/desktop-capture-sample/mhkidniocjdaiddjckopkigjmjbadfji
I added this app to chrome, opened it and clicked Start Capture.

What I found was that the problem occurred across all 4 of the apps/sites in Ubuntu, but was not present in Windows 7. I have put together a set of pictures showing these results along with a summary at:
https://drive.google.com/drive/folders/0BylSpmaxch5dM3gtempxb3lvQ0k?usp=sharing 

Despite my inexperience and busy college life, I am committed to doing whatever I can to help get this issue solved, so if anyone wants more info from me, please let me know. I would be happy to put in the legwork to make the coding work as easy as possible. I will also be watching this bug over the next several days/weeks/months.

Thanks,

Oh, and I forgot to say that shouldn't the title of this bug include “Linux” somewhere? I feel that that would be more descriptive since it does seem to be related to Linux.

It is such a good point to add a word "Linux" to the title. Unfortunately, it seems that I cannot edit the title once an issue is filed. If anyone knows how, let me know. I would be happy to make a change.

I can confirm that this bug exists in Linux 14.14

Hi all, Just recently, I had an idea that, if implemented across all desktop-style platforms, might provide somewhat of a work-around to this issue. Thus, I opened a separate bug report/feature request to see if it might be possible to implement. It is  issue #668852  Clearly it isn't a full solution, but I thought you might want to know about it none the less.

With a 3 screen setup the issues sharing screen is really troublesome.
Currently I have to disconnect all other screens before doing a screen share because I need to share my desktop.

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	Screenshot from 2016-12-14 09-08-12.png 138 KB View Download

This seems more like a feature request and hence marking it as untraiged , So that respective tesm would look into this.

Thanks!

This feels more like a bug than a feature. Linux is the only environment that is unable to share a screen. You can share a screen in Windows and MacOS. There is missing functionality that makes the user experience incongruent.

I would tend to agree with Comment #8 that this is more of a bug than a feature request. Functionality is indeed missing on Linux that is available on other operating systems.

I agree. This is not a feature request. This feature already exists and works in Windows and MacOS. hdodda@chromium.org, please re-consider marking this as a bug and escalating. This bug makes collaboration via screen sharing unusable for Linux users. Comment #1 has a *very* good description of the problem with links to screenshots.

Concur, this is a bug, not a feature; feature-parity is missing in this regard -- X11 proto/spec supports this; Mac OS has it outside of X11 proto I imagine.

XRandr 1.5 introduced "Monitors" to X11 proto; that is worth mentioning, though I suspect _that_ support could be chopped off as a feature (as it seems a concept specific to X11; not sure there's a counterpart w/ Mac OS or Windows).

https://cgit.freedesktop.org/xorg/proto/randrproto/tree/randrproto.txt#n152

This is really annoying. Same Problem on
OS: Arch Linux 4.11.3-1
google-chrome 58.0.3029.110-1
google-talkplugin 5.41.3.0-1

Same issue on
OS: Ubuntu 16.04 (64-bit)
Chromium: 59.0.3071.109 (Developer Build)

Please, fix!

This issue was mentioned in an issue from another project: https://github.com/crmarsh/discord-linux-bugs/issues/220#issuecomment-322031019

Same problem on Arch Linux:
chromium 62.0.3202.62-1
linux 4.13.7-1

installing google-talkplugin doesn't change anything. I wasn't able to found suitable workaround, have to manually disconnect other displays :-/

Its been almost 3 years and this problem in Chrome has not been fixed for Linux. Could it be an issue with hybrid systems

nonsense.. googlr just likes being shown up by bluejeans

Hi,

Just wished to kindly emphasize that the reported behaviour really is an issue, not a feature-request, as it makes Linux-based hangouts' screen sharing sessions fundamentally broken on multiple screens setups when compared to what's available on Windows and MacOS — meaning, crowd's not been asking for a new feature to be added, but for an existing, broken feature to be fixed.

Is there a way to push that issue up the stack in an efficient and "chromium's-law-abiding" manner, and/or get developer feedback as to the feasibility of a fix?

As a workaround I use ffmpeg virtual webcam. I have written a script that asks you which individual screen you wish to share.
Chromium will not automatically add virtual webcam to its list (its another bug), so to workaround it, I prorammatically reinsert my internal laptop webcam.
I have shared these scripts in my repo called hliss (Hangouts Linux Individual Screen Share). It is located here: https://github.com/Ashark/hliss

Indeed this is not a feature request, as this functionality is already available, but don't work on a specific platform. It affect me as discord uses the API and cannot share one screen.

Can anyone at Google review this? It's been open for really long and xrandr (1.5) has the right API so this bug can be fixed.

google nolonger has employees... there are only AI bots. and AI bots dont care man. Nothing to gain from actually creating quality software that people can use these days. their primary focus is just to spy on you for marketing and espionage purposes. 

yes i know COC before i even get that argument. my counter argument is the truth is always constructive.

Given that this issue is no longer comprehensive of the scope of this bug (really, it is a bug within the chrome.desktopCapture API), and given the stagnation of this issue, I've opened a new bug tracker here: https://bugs.chromium.org/p/chromium/issues/detail?id=874340

Stars are very helpful, but please refrain from commenting unless you have information to add onto the already listed information.

I may have made a mistake in the information I included; I mostly was summarizing the bug, where it manifests, and some references to the bug. Many of you have a stronger grasp of the issue here; if you have any corrections to the information I included, please comment on the new tracker!