Guest display auto-resize dit not work anymore

[Laurent Simon]

Guest display auto-resize worked perfectly for years (Windows 10 guest on Kubuntu 14.04 host). Since upgrade to VirtualBox 5.1.26 r117224 (from 5.1.24 r117012), the display resolution is not evaluated properly.

At startup the VM display resolution is wrong in fullscreen mode (1920x1080 instead of 1340x1440 on the host). There is no way to set it manually in Windows display properties settings. The maximum proposed resolution is 1920x1080. The host resolution (1340x1440) is not present in the proposed list.

The following workaround works:

• Disable "Auto-resize Guest Display"
• Enable it again immediately (without any screen mode change before)

Then the guest window is set to the proper resolution (and this resolution become available in the Windows display settings).

Remark: there is another bug. Just after the VM startup (in fullscreen mode), this workaround cannot be applied directly. In the mini bar, the "Auto-resize Guest Display" option is not clickable (like if it was disabled). Pressing <host>-F (to exit fullscreen mode) then pressing <host>-F one time again (to get back in fullscreen mode) fixes it. The "Auto-resize Guest Display" option become operable.

The effect of the workaround is very volatile. If, for any reason, the guest display resolution is reevaluated, then the correct resolution is lost. For example, in all the following situations (but not limited to), the correct resolution is lost and the workaround has to be applied again to recover the correct screen resolution:

• The VM state is saved and the restored later
• The VM window is minimized and then restored on the host.
• The guest screen mode is changed (any mode), then restored to fullscreen.
• ...

Apparently, any action that conduct to reevaluate the guest display resolution bring back a wrong one (except if you are lucky and have a 1920x1080 display). The workaround must be applied again to get back to the correct screen resolution.

Environment

Host

• OS : Ubuntu 14.04.1 (88~14.04.1-Ubuntu SMP Fri Jan 13 14:54:07 UTC 2017 )
• Kernel release: 3.19.0-80-generic
• Platform: x86_64
• Desktop: KDE (kubuntu-desktop)
• KDELibs Version: 4.13.3
• Qt version: 4.8.6
• VirtualBox version: 5.1.26 r117224

Guest

• OS: Windows 10 Pro
• Version: 1703 15063.483
• Platform: x64
• VirtualBox Guest Additions: 5.1.26

[Laurent Simon]

Log of VM startup that brings incorrect resolution (and inoperable "Auto-resize GuestDisplay" option)

[Laurent Simon]

The same log, after applying the workaround