Win10 Quick Assist screen-share shows corrupted desktop

[Jim Avera]

If Windows 10 guest shares its screen with a remote user using the built-in "Quick Assist" utility, the other user sees a corrupted screen. Specifically, everything is slanted at a 45 degree angle (see screenshot). It looks like each horizontal row of pixels is offset slightly from the previous one.

HOST: Ubuntu linux 20.04, X-org, Intel graphics GUEST: Windows 10 64-bit

STEPS TO REPRODUCE: In some other Win10 machine (VM or real):

1. Start the "Quick Assist" app.
2. Click the "Assist another person" button at the bottom (sign in to a microsoft account if prompted) Note the "Security code" number displayed

In the Vbox VM Win10 guest:

3. Start "Quick Assist"
4. Enter the Security code in the "Code from assistant" box

RESULTS: The remote Win10 sees the VM guest's desktop in an unusably skewed form

[Jim Avera]

Screenshot on remote system showing corrupted display

[Jim Avera]

Virtualbox Version 6.1.12 r139181 (Qt5.12.8)

(wasn't offered as an option in the drop-down)

[Jim Avera]

Still reproduced using VirtualBox 7.0, either between a VM and bare-metal system or two VMs. It seems to depend on certain screen-size ratios. I suspect (not sure) that the bug occurs when the "assisting" system's screen is vertically taller than the "assisted" machine's screen.

I will attach a screenshot showing the problem with two Win10 VMs running as guests on linux host.

The overall window sizes *on the host* (from xwininfo) were:

[upper left] "assisted" : Width: 1331, Height: 529
[lower right]"assisting": Width: 1073, Height: 724 (corruption visible)

Note that the "assisted" machine (in upper left) is vertically shorter than the "assisting" machine in lower right.

I though this might be a Microsoft bug unrelated to VBox video, although at this point it would be surprising because their own support people would suffer from it. I tried a VM "assisting" machine with large screen and a smaller bare-metal (laptop) "assisted" machine and did not see the problem. Obviously not conclusive, but it's one datapoint indicating that the problem has somehow to do with VBox video on one end. Especially because the problem *did* appear the other way around, i.e. if the VM window was vertically shorter than the laptop's screen. Sorry but I don't have a large-screen bare-metal Windows box...

I hope this helps.

[Jim Avera]

Two win10 clients showing "slanty" corruption