Guest Windows Slowly Shrink Vertically to 103 pixels and Jump Around on Resize

[PHands]

Hi,

I started a thread on the Community Forums on this on Sept 3rd, and despite some excellent questions from Volunteer fth0 in Germany, I think it's time for a bug report.

The trail on community is at ​https://forums.virtualbox.org/viewtopic.php?f=7&t=99659. It includes a small video of the shrinking guest windows, plus a bunch of Log files.

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SUMMARY

I just upgraded to V 6.1.12 r139181 and I'm seeing some very odd behavior in guest windows. A subsequent upgrade to Version 6.1.14 r140239 (Qt5.14.2), including the extpack and Guest Additions, has not changed anything.

DETAILS

Guest windows jump around randomly at irregular times, and guest windows slowly shrink vertically unless maximized after a resize. Over a period of 15 - 20 minutes, a guest windows shrinks, vertically only, until it's 103 pixels in height. It seems to shrink 1 or 2 pixels at a rate that appears dependent on the host machine's loading, but often around every 1 or 2 seconds. This makes it impossible to do much with the guest OS, because any menu picks get removed by the window redraw before an option can be chosen.

Horizontal size seems to be irrelevant. Scale factor in Display Setting for all guests is 100%.

If I resize a guest window, it will jump elsewhere randomly - often to another screen or straddling two monitors, and then start shrinking.

This happens on both Windows and Linux guests, with VBoxVGA and VBoxSVGA graphics controllers. It has only started since the update to the 6.1.12 and 6.1.14 versions...all was fine before that.

The host machine is an 8 physical core (16 virtual) AMD Ryzen 7 2700X PowerSpec G162 with an AMD Radeon RX580 GPU, with 48G RAM and 15Tb Storage so it can handle the VBox load. The machine is running KDE Neon 5.19.4, which is KDE's own distro, based on Plasma 5.19.4 and the 5.14.2 Kernel. I have compositing switched on for full KDE effects. I have 3 4k Monitors, although I don't think that's relevant.

The Log files contain large numbers of repeats of these lines, with the X size reducing by 1 or 2 pixels each time, until 103 is reached.

00:04:30.078206 GUI: UIMachineView::sltPerformGuestResize: Sending guest size-hint to screen 0 as 2245x103 if necessary
00:04:30.182443 VMMDev: SetVideoModeHint: Got a video mode hint (2245x103x32)@(0x0),(1;0) at 0
00:04:30.182825 VMMDev: Guest Log: Got multi resize request 1 displays
00:04:30.182851 VMMDev: Guest Log: [0]: 0 0x39 0,0 2245x103 32
00:04:30.194294 GUI: UIMediumEnumerator: Medium-enumeration finished!
00:04:30.205602 Display::i_handleDisplayResize: uScreenId=0 pvVRAM=00007f9698000000 w=2245 h=103 bpp=32 cbLine=0x2314 flags=0x1 origin=0,0

At fth0's suggestions, I tried setting extradata to various initial window sizes, to see if that affected the shrinking behaviour, but it hasn't made much difference.

[PHands]

Video of the shrinking

[PHands]

Sorry about adding the video twice - can't see how to remove the attachment. There are also a couple of log files attached. I'm also happy to do a Zoom screen share, if anyone wants to see it live.

[Frank Batschulat (Oracle)]

You wrote:

This happens on both Windows and Linux guests, with VBoxVGA and VBoxSVGA graphics 
controllers. It has only started since the update to the 6.1.12 and 6.1.14 versions.
..all was fine before that. 

The systems default adapter that should be used with Linux guest is VMSVGA, not VBoxVGA and not VBoxSVGA. Please try the Linux guest with VMSVGA instead.

[PHands]

Replying to fbatschu:

You wrote:

This happens on both Windows and Linux guests, with VBoxVGA and VBoxSVGA graphics 
controllers. It has only started since the update to the 6.1.12 and 6.1.14 versions.
..all was fine before that. 

The systems default adapter that should be used with Linux guest is VMSVGA, not VBoxVGA and not VBoxSVGA. Please try the Linux guest with VMSVGA instead.

What is the preferred adapter for Windows10? The W10 guest has VBoxSVGA, and is showing the same problems.

P

[PHands]

Replying to fbatschu:

You wrote:

This happens on both Windows and Linux guests, with VBoxVGA and VBoxSVGA graphics 
controllers. It has only started since the update to the 6.1.12 and 6.1.14 versions.
..all was fine before that. 

The systems default adapter that should be used with Linux guest is VMSVGA, not VBoxVGA and not VBoxSVGA. Please try the Linux guest with VMSVGA instead.

I have a KUbuntu Guest with the VMSVGA adapter. It shows the same problem.

[PHands]

Just updated VBox to Version 6.1.16 r140961 (Qt5.15.1) and the shrinking behavior is still happening on a Windows 10 guest with the VBoxSVGA Graphics Controller, an OpenSuSE Leap 15.2 guest with VMSVGA and Linux Mint 20, also with VMSVGA, and a few other Linux distros. All were tested after installing the latest Guest Additions. It's worth noting that a shrinking window - running any guest OS - stops shrinking if the window is moved, without resizing, by some minimum distance. I don't have any easy way of determining what that minimum is.