1681523 - Cannot share individual windows with WebRTC conference in Qubes

Status: NEW

(Core :: WebRTC, defect, P5)

Description

[benjaminmoody]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

1. Create a video conference on https://meet.jit.si/.

2. Click the "share your screen" button.

Actual results:

Firefox displays a popup below the address bar, asking to confirm the operation. The popup says:

Will you allow meet.jit.si to see your screen?

Window or Screen to share:
[Select Window or Screen]

[] Remember this decision

[Don't Allow]  [Allow]

"Select Window or Screen" is the default option selected in the combobox. The "Allow" button is grayed out. If I click on the combobox, I see it has two options:

Select Window or Screen   (grayed out)
Entire Screen

Expected results:

It appears that what should be happening is that a list of all other application windows should be shown in this list. They aren't.

In other words, I am not able to select a single window to share; instead I'm shown this confusing and apparently non-functional UI.

I am guessing that this is happening because I'm using a window manager (qubes-gui) that is non-reparenting. Whatever mechanism Firefox uses to enumerate the windows on the desktop, it assumes that a window manager is running that moves each toplevel window into a child window that's owned by the window manager. Although this is common, it's not necessary; it's not the case for all window managers, and in particular it's not the case in Qubes.

I'd be happy to provide a fix, or try to, if anyone can point me to the code responsible for enumerating windows on X11 and capturing their contents.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Comment 2

[benjaminmoody]

Actually, it sounds like this is a bug in the qubes-gui window manager (i.e. it's not following ICCCM requirements - not Firefox's fault, though it might be nice to have a fix on the Firefox side anyway.)

See https://github.com/QubesOS/qubes-issues/issues/5789 for some details and possible workarounds.

Comment 3

[Michael Froman [:mjf]]

Jan-Ivar, does this sound like something we can work around?

Comment 4

[Jan-Ivar Bruaroey [:jib] (needinfo? me)]

I wouldn't know, but it sounds like this is already being worked on in https://github.com/QubesOS/qubes-gui-agent-linux/pull/121 🙌

I'd be happy to provide a fix, or try to, if anyone can point me to the code responsible for enumerating windows on X11 and capturing their contents.

From what I recall from bug 1675764 that's deep in libwebrtc, though any changes there should be coordinated with dminor (cc'ed) since we have a merge coming up.

Comment 5

[Dan Minor [:dminor]]

It would be best if a fix was made against upstream libwebrtc (https://webrtc.googlesource.com/src/+/refs/heads/master/docs/native-code/index.md). Once landed, let us know, and we can backport the fixes. I think this is the code you are looking for: https://webrtc.googlesource.com/src/+/master/modules/desktop_capture/linux/window_list_utils.cc. The desktop capture code is an area where we've made a number of local changes, so it's possible that the fix will be Firefox specific, but in this case, I think upstream is the place to start looking.

Comment 6

[Dan Minor [:dminor]]

I'll leave this open so we can track any fixes made upstream.