Screensharing in AppVMs

[DemiMarie]

Qubes OS version:

R4.0

Affected component(s):

domU GUI

---

Steps to reproduce the behavior:

Use Slack Desktop with screensharing

Expected behavior:

Screensharing works, in that it can share any screen space belonging to the AppVM

Actual behavior:

Screensharing fails

General notes:

This was an issue for me during an interview. Probably the best solution is to allow running a full Linux desktop environment in a single Qubes window.

---

Related issues:

[marmarek]

Some details from @v6ak on the current state: https://groups.google.com/d/msgid/qubes-users/626cd5a7-97b0-497b-8d85-2eb7df9e9402%40googlegroups.com

[marmarek]

Right now any attempt to capture the screen from inside qube (either screenshot or some screen sharing) results in just white image.
I've found why: we enable composition in "manual" mode. According to XCompositeRedirectSubwindows manual:

The rendering of an entire hierarchy of windows is redirected to off-screen storage.

So, the actual screen isn't draw. That's fine for gui-agent, which access those per-window off-screen storage, but breaks grabbing screen content.

There is also automatic mode:

When a hierarchy is rendered off-screen, the X server provides an automatic mechanism for presenting those contents within the parent window.

And changing it does fix this problem. But I also suspect it will affect performance because now the whole screen needs to be rendered twice (once in the AppVM and then in dom0). I need to check that and depending on results make it optional.

[marmarek]

Not very scientific test: firefox with the same video and other settings. CPU usage for both VMs (with the change and without) is pretty much the same.

[ioleo]

@marmarek maybe this could be exposed as a AppVM setting? I've got about 20 AppVMs, but actually only need to screenshare from one. I mean, if there is a performance penalty, one might want to pay it only where we actually need it.

[ioleo]

Thank you very much for this! @marmarek 🎉 👏
I'll try to update qubes-gui-agent from testing repositories tomorrow and test it. I'll let you know.

[v6ak]

There used to be update notifications from a bot. In this issue, I don't see any, which most likely means it is not yet in the repo.

[ioleo]

@v6ak I see. The command sudo dnf update qubes-gui-agent --enablerepo=qubes-vm-r4.0-current-testing actually shows that there is an update available:

================================================================================
 Package            Arch      Version            Repository                Size
================================================================================
Upgrading:
 qubes-gui-agent    x86_64    4.0.17-1.fc28      qubes-vm-r4.0-current     54 k
Installing dependencies:
 python3-xcffib     noarch    0.5.1-5.fc28       fedora                   192 k

Transaction Summary
================================================================================
Install  1 Package
Upgrade  1 Package

But I suspect it might be anything else :)

[marmarek]

This will be in 4.0.18. And also 3.2.29 some time later.

[qubesos-bot]

Automated announcement from builder-github

The package gui-agent-linux has been pushed to the r4.0 testing repository for the CentOS centos7 template.
To test this update, please install it with the following command:

sudo yum update --enablerepo=qubes-vm-r4.0-current-testing

Changes included in this update

[qubesos-bot]

Automated announcement from builder-github

The component gui-agent-linux (including package pulseaudio-qubes-4.0.18-1.fc26) has been pushed to the r4.0 testing repository for the Fedora template.
To test this update, please install it with the following command:

sudo yum update --enablerepo=qubes-vm-r4.0-current-testing

Changes included in this update

[qubesos-bot]

Automated announcement from builder-github

The package qubes-gui-agent_4.0.18-1+deb9u1 has been pushed to the r4.0 testing repository for the Debian template.
To test this update, first enable the testing repository in /etc/apt/sources.list.d/qubes-*.list by uncommenting the line containing stretch-testing (or appropriate equivalent for your template version), then use the standard update command:

sudo apt-get update && sudo apt-get dist-upgrade

Changes included in this update

[ioleo]

@marmarek @v6ak I can confirm it works using vncserver and dwm locally (as per daves blog except all in one VM / without the inter-vm stuff - I don't need that).

[ioleo]

@marmarek @v6ak I can confirm it also works without those stuff. You're seeing all windows of your AppVM, but everything around is white. Which is actually really cool!

[ioleo]

Thanks again for this great feature @marmarek <3

[succdo]

Nice features, Thanks for implementing this important features.
Looking forward to new release for R3.2.

[qubesos-bot]

Automated announcement from builder-github

The component gui-agent-linux (including package pulseaudio-qubes-4.0.18-1.fc26) has been pushed to the r4.0 stable repository for the Fedora template.
To install this update, please use the standard update command:

sudo yum update

Changes included in this update

[qubesos-bot]

Automated announcement from builder-github

The package qubes-gui-agent_4.0.18-1+deb9u1 has been pushed to the r4.0 stable repository for the Debian template.
To install this update, please use the standard update command:

sudo apt-get update && sudo apt-get dist-upgrade

Changes included in this update

[qubesos-bot]

Automated announcement from builder-github

The package gui-agent-linux has been pushed to the r4.0 stable repository for the Fedora centos7 template.
To install this update, please use the standard update command:

sudo yum update

Changes included in this update