Open Bug 1672126 Opened 4 years ago Updated 3 years ago

webRTC: mouse pointer displayed at wrong position on shared screen

Categories

(Core :: WebRTC, defect, P2)

Desktop
Windows
defect

Tracking

()

Tracking Status
firefox86 --- affected

People

(Reporter: mathematikus, Unassigned)

References

(Blocks 1 open bug)

Details

(Keywords: multi-monitors)

Attachments

(5 files)

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:81.0) Gecko/20100101 Firefox/81.0

Steps to reproduce:

  • use a Windows PC with two monitors attached (maybe other OS also "work")
  • configure the two monitors in the Windows settings to be "side by side", but one monitor "lower" than the other one (see attached screenshot)
  • start Firefox
  • share one of your monitors via webRTC. For a reproducible example, visit the following link with firefox and "start the demo code there": https://webrtc.github.io/samples/src/content/getusermedia/getdisplaymedia/
  • choose the left monitor (the one that is set slightly lower in the windows screen settings) to share
  • move the mouse pointer onto this shared screen. Move it around.
  • compare the position of the mouse pointer on the "real" shared screen, and the moving image inside the browser window showing this very same screen.

Actual results:

The position of the mouse pointer on the "real" screen is DIFFERNT than the position of the mouse pointer as shown in the browser windows showing the shared screen. (I will try to attach two more screenshots to visualize this)

Expected results:

Both positions of the mouse pointer should be the same.

Addidtional information:
This is important for the (now very common) video conferencing tools, that use WebRTC inside a browser. When you share a slide show on your screen, you often want to "highlight" something with the mouse pointe. With Chrome this works fine, with Firefox it doesn't.
I first observed this with the (open source) video conferencing tool "BigBlueButton", see this link to the original bug report: https://github.com/bigbluebutton/bigbluebutton/issues/10661 (This BBB bug report is now closed, because they agreed this is a Firefox bug, not a BBB bug.)

Component: Untriaged → WebRTC
Keywords: multi-monitors
OS: Unspecified → Windows
Product: Firefox → Core

I tried this on a Windows 10 laptop connected to an external display. I don't see the mouse pointer when capturing the second display, but I see it when capturing the laptop built-in display.

Dan, do you have any thoughts on this?

Flags: needinfo?(dminor)

Since this is working in Chrome, I think at this point it probably makes sense to wait until after we do the libwebrtc update and see if that fixes things in Firefox as well.

After doing an OS update, my old Windows laptop now blue screens every single time I try to do any screen/window sharing, so I'm not really in a position to investigate this further right now. It might be a simple backport if someone has spare cycles to spend on this.

Severity: -- → S3
Flags: needinfo?(dminor)
Priority: -- → P3
Status: UNCONFIRMED → NEW
Ever confirmed: true

I'm on Windows 10 and Firefox 84 with the following screen composition:

When I'm sharing the middle screen, the cursor is missing. When I move it to the right screen, it becomes visible in the shared video.

Managed to reproduce the issue using Windows 10x64 PC with 2 external displays on Firefox 86.0a1.

QA Contact: gasofie
Hardware: Unspecified → Desktop
Version: Firefox 81 → Trunk

Gabi, is this reproducible on two screens or three? Can you provide some good str.

Flags: needinfo?(gasofie)

I have reproduced the issue with Windows 10x64 PC with 2 external monitors and with Windows 10x64 laptop with 2 external monitors.
STR:

  1. Configure the monitors displays to be side by side but the second monitor drag it to be higher than the first (as in "Windows display settings for the two monitors" attached image)
  2. Open Firefox Nightly on the second monitor
  3. Open https://webrtc.github.io/samples/src/content/getusermedia/getdisplaymedia/ in Firefox Nightly
  4. Hit start sharing button and select the Screen 1
  5. Go to screen 1 and observe/compare the mouse pointer position in both screen 1 and shared screen

Actual Result: Mouse pointer position in the webRTC shared screen is higher within the page

Expected Result: The mouse pointer position should be the same in both screen 1 and the shared webRTC screen

Flags: needinfo?(gasofie)
Priority: P3 → P2
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