[Bug]: Virtualbox guest window is defective when at forefront - Ubuntu Mate 20.04 host

[Madpentiste]

Version

7.2.4

Host OS Type

Linux

Host OS name + version

Ubuntu 20.04 LTS with MATE environment

Host Architecture

x86

Guest OS Type

all

Guest Architecture

x86

Guest OS name + version

N/A defect appear with any guest, and even without any guest (empty virtual machine, just created, with no OS)

Component

GUI

What happened?

This bug resembles, but is not identical to, https://www.virtualbox.org/ticket/22204

When the Virtual Machine (guest) window is on top of every other windows (active / at forefront), it looses several capabilities :

• it cannot be displaced/moved
• it cannot be resized manually in any direction
• the window menu triggered by a click on the small button at top left corner of window frame is no longer available, hence additional actions are also lost.

This issue disappears if :

• An Xfce environment is used, instead of Ubuntu ; in my case, I tried Xubuntu.
• The active/top/forefront window is NOT the Virtual Machine one -- to reproduce this tricky finding, one must put at the forefront a window that will not hide completely the VM window frame ; hovering over the VM window frame will show (in info bubble or pointer shape change) the desired capability, which can be executed then by clicking ; after that, since the VM window will be the active one, these capabilities will be lost again, to be only back if another window is activated.

How can we reproduce this?

On an Ubuntu-Mate 20.04 host, launch the VitualBox application, and then launch whichever virtual machine of your choice. Keep the VM window as the active one.

1. Try to move the VM window ; the window will stay put.
2. Try to change the size of the window, by an edge or a corner of the frame : nothing will happen.
3. Try to get the "window" menu by clicking on the small button in the top left corner of the frame : no menu.

Then do anything that will put another window at the forefront, but keep visible at least the top of the VM frame and try any of the above (1,2,3) actions : success at first attempt. Subsequent attempts will fail again, since the VM window will be now the active one. You need to activate another window to be successful again.

On an Xfce 20.04 environment, repeat the above : no issue.

The attached log is with an empty machine (new machine without guest OS), in order to have the log the least verbose possible, with only actions on windows.
Vide pour tests-2026-01-15-18-55-40.log

Did you upload all of your necessary log files, screenshots, etc.?

• Yes, I've uploaded all pertinent files to this issue.