[Bug]: VirtualBox wont automatically adopt the new system theme on relaunch

[lijh8]

Version

trunk/main

Host OS Type

macOS

Host OS name + version

macOS 12.7.6 (21H1320)

Host Architecture

x86

Guest OS Type

Linux

Guest Architecture

x86

Guest OS name + version

Ubuntu 25.10

Component

GUI

What happened?

If I shut down my computer at night while macOS is in Dark theme and restart it the next morning when macOS has switched to Light theme, VirtualBox still appears in Dark theme. Specifically, its title bar (which is controlled by macOS) is light, but the rest of the window remains dark.

This is what currently works: if I manually switch between Light and Dark theme in macOS settings while VirtualBox is running, VirtualBox will switch its theme accordingly.

However, it seems that VirtualBox remembers and uses the theme it was using when it last ran--if it doesn’t experience a theme change during its session, it won’t automatically adopt the new system theme on relaunch.

Sorry that I did not report this thoroughly last time (Issue #457). I rely on VirtualBox to try the latest GCC and Clang compilers on Linux, as my Mac mini (2014) is unsupported by Apple. Thanks for the great work on VirtualBox.

VirtualBox Version 7.2.6 r172322 (Qt6.8.0 on cocoa)
macOS 12.7.6 (21H1320)
Mac mini (Late 2014)

How can we reproduce this?

As provided

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

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