Thank you for addressing this issue. To add a few additional points and a use case:

This behavior happens on each and every Chromebox tested, not just the original platform mentioned.

This behavior happens regardless of the make/model/type of second monitor (e.g. reproduced with different manufacturer's products as well as projectors).

Use case: we transitioned our teachers from Windows desktops to Chromeboxes; classrooms have a touch panel in the front of the room and desktop monitor at the teacher desk. Desired use is for extended mode so class content can be displayed (and interacted with through touch) on the touch panel and teacher can work on other content on desktop monitor.

Thank you for your consideration on this issue.

This is a long standing issue.
See the following:
https://bugs.chromium.org/p/chromium/issues/detail?id=589989
https://bugs.chromium.org/p/chromium/issues/detail?id=606742
https://bugs.chromium.org/p/chromium/issues/detail?id=613022
https://bugs.chromium.org/p/chromium/issues/detail?id=684178

From what I've been able to gather, there are instances where the touchscreen events aren't properly positioned when in a dual monitor setup. There was supposedly some work on getting some settings/configuration UI in place to manage calibration and ensure proper touch placement. It has been a while since I last heard anything about work being done on this though.

I would love to see a fix implemented as I have a touchscreen monitor that has been 'untouched' for almost a year and a half. 😉

Is there an update on this issue?

We have a customer reporting this issue on AOpen Chromebox Commercial. They confirmed that touch capabilities are not detected when two monitors are connected, even if the two monitors are touch.

Isuse has been replicated on Chrome OS 56 nad 60. In additiona, they have some devices running an old version of Chrome OS (48) where touch capabilities are working as intented.

If there is any additional info we can provide to help with the investigation, please let me know.

Hi! I have the same problema...

Is there an update on this issue?

We have a customer reporting this issue on AOpen Chromebox Commercial. They confirmed that touch capabilities are not detected when two monitors are connected, even if the two monitors are touch.

Isuse has been replicated on Chrome OS 56 nad 60. In additiona, they have some devices running an old version of Chrome OS (48) where touch capabilities are working as intented.

If there is any additional info we can provide to help with the investigation, please let me know.

Let's triage again.

Yes, please re-evaluate this; this issue (technically a regression, as the functionality worked in previous versions of ChromeOS) is preventing us from moving 100 teachers from Windows to ChromeOS - we are Chromebook school and it's rather silly to have to require our teachers to use Windows just so they can use touch on their interactive boards!

Thanks in advance!

This should have been resolved by  bug 667921 .

Touch used to get disabled when connecting multiple external touchscreens (except via UDL) as we had no way to associate the touch inputs to the correct display, but IIRC that's been working for a while now.

malaykeshav@ any idea what's up here?

Touch screen association is still based on heuristics (crbug/599985)
If the screens have similar resolution, this association may fail. 

+tbuckley

No, this issue is absolutely not resolved.

I enabled touchscreen calibration flag and restarted but made no difference. However, after restart (with both monitors connected) I did not see a calibration option; when I unplugged the standard (non-touch) monitor the Calibration option appeared. Similarly, when I plugged the non-touch monitor back in the Calibration option disappeared (on both monitors).

Note: I also tried setting "Touch Events API" to Enabled but it made no difference. 

Per comment 13 - this may be our issue, as both displays have 1080p resolution.

Yes. If the system fails to associate a touch device with a display, it simply ignores the touch device all together. This is also why we do not see the touch calibration settings which needs a touch device associated with display.

@malaykeshav to confirm:
1) if there is an unpaired touchscreen, we should still show the "Calibrate" option for each display in Display Settings
2) if the user taps an unpaired touchscreen after clicking "Calibrate", that touchscreen should be paired with the selected display

Is there an update on this issue?

I have the same problem. When I only attach the touchscreen to the HDMI port touch is working. When I attach a second monitor touch fails. Even when the second monitor is non touch the touch fails on the touchscreen when HDMI and DP are used simultaneously. 
We now have solved this issue by using a HDMI splitter. This works good with a resolution of 1920x1080. But we also have 4K touchscreens and that is a totally different story. 
- sometimes the screens go black for a moment
- video playback is not working in 4K (I will open a new issue for this since 4k video playback is not working right at all even if I just connect the two screens to the HDMI and DP). It seems to be a restriction of the GPU of the Chromeboxes we use. 

So know we use 4K screens on 1920x1080. So solving the touch issue is very important to us. Then we can remove the splitter.
 

A splitter is our workaround too; a StarTech ST122HD4KU splitter (powered by AC adapter) works for us for 4k content. However, our users (teachers) sorely miss the ability to extend their screens, they cannot work on anything confidential without powering off their student-facing touchscreen displays. Not sure what we'll do with all our splitters once the issue is resolved, we had to put one in every classroom!

The status is 'started' so hopefully we will see a resolution soon! Thanks, malaykeshav!

I have tried exactly those splitters but they didn't work with our prowise Proline series. Now I have the ATEN VS182A. This works, but only 4K on 30Hz. Because of the 30 Hz writing on the screen becomes slow and videoplayback is lagging all the time.

This should be fixed following versions above 64.0.3271.3.

Once enabled, chrome://flags/#enable-touch-calibration-setting (Still an experimental feature), any device with an external touch display should be able to associate it to any non-internal display. This association would persist across system restarts. It will also remember the ordering of association for convenience in the future.

 Issue 806354  has been merged into this issue.