Windows HVM does not show in dual-head setup with one monitor in portrait mode

[lorenzog]

Qubes OS version (e.g., R3.2): 3.2, XFCE

Affected TemplateVMs (e.g., fedora-23, if applicable): N/A

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Expected behavior: Starting a Windows HVM should show the Windows desktop regardless of the number of displays in dom0 or their orientation.

Actual behavior: Windows is running (qrexec connected, etc.) but the windows desktop does not show if there are two monitors and one is in portrait mode.

Steps to reproduce the behavior:

[requires a dual-head setup]

1. Disable the secondary display (System Tools -> Display -> untick 'use this display')
2. Fully install a Windows HVM with only one display enabled (with Qubes Tools)
3. Confirm Windows boots regularly
4. Enable the second display
5. Confirm this resolution
6. In the display layout, drag the second display to the left of the primary one, set the rotation to 'left' and drag again so that they form a top-left corner
7. Apply
8. Start the Windows HVM
9. The Windows HVM will be running, but not showing (e.g. it can be stopped with the VM manager)

To make it work:

1. Disable secondary display
2. Start Windows
3. Enable display
4. The Windows HVM window can now be dragged to either monitor and it shows its full resolution in vertical and horizontal mode

General notes:

By trial-and-error I think the problem is in the resolution: with a dual monitor layout, and when monitors have different H/V resolutions, it "feels" like Xen is trying to pass the full monitor resolution by adding all horizontal and vertical pixels; and Windows refuses to boot.

Same issue happens with i3 (thus excluding XFCE as the main culprit).

Running applications in seamless mode does not change the behaviour: the application does not show up.

Related issues:

[andrewdavidwong]

Sounds somewhat reminiscent of #1896.

[andrewdavidwong]

Sounds somewhat reminiscent of #1896.