Ticket #20535 (new defect)

Opened 15 months ago

Last modified 15 months ago

W64 host, Ubuntu guest: mouse cursor corrupt in Terminal on secondary 4K screen

Reported by: JonAtFS Owned by:
Component: other Version: VirtualBox 6.1.26
Keywords: Cc:
Guest type: Linux Host type: Windows

Description (last modified by janitor) (diff)

System details at the end.

Whether the VB container window is sized very small or large, there is a glitch with the mouse cursor inside Terminal windows in the guest OS.

Note that there are two 4K monitors attached. This bug only appears if the VB container window is on one of the secondary monitors. If it is on the laptop's main screen, the cursor simply disappears when typing, which I believe is the desired behaviour.

The specific issue is as follows: once the mouse cursor is moved inside the Terminal window, it is at first correct. However, type as much as one character, and it turns into a block of glitched data, 8-10 characters wide and one character tall. If the cursor is moved even a tiny amount, it returns to normal, until the user types once again.

I've attached images of the before and after effects within a small VB container window.

It appears that when the cursor is being removed, the underlying pixels are being bitblt'ed from the wrong part of video memory.

System details

VB 6.1.26 build 145957 (Qt5.6.2)


  • Edition Windows 10 Pro
  • Version 20H2
  • Installed on ‎06/‎07/‎2021
  • OS build 19042.1165
  • Experience Windows Feature Experience Pack 120.2212.3530.0


  • Ubuntu 64 bit Hirsute, all patches current
  • VM Additions installed.


  • Processor Intel(R) Core(TM) i5-7200U CPU @ 2.50GHz 2.71 GHz
  • Installed RAM 8.00 GB (7.88 GB usable)

System type 64-bit operating system, x64-based processor


  • HP EliteBook 840 G4
  • 3 GiB RAM assigned to guest
  • Main screen: 1080p inbuilt
  • Secondary screens:
    • 2x 28" 4K
    • full resolution
    • 125% scaling
    • both connected using DisplayPort.


glitch-before.jpg Download (225.4 KB) - added by JonAtFS 15 months ago.
Cursor normal, before the user types anything
glitch-after.jpg Download (263.6 KB) - added by JonAtFS 15 months ago.
Cursor corrupted after typing

Change History

Changed 15 months ago by JonAtFS

Cursor normal, before the user types anything

Changed 15 months ago by JonAtFS

Cursor corrupted after typing

comment:1 Changed 15 months ago by JonAtFS

(Apologies for poor quality images, by the way. Whichever way I tried to screencap the results appeared to prevent them being captured, so I had to take phone pictures instead.)

comment:2 Changed 15 months ago by janitor

  • Description modified (diff)

comment:3 Changed 15 months ago by janitor

As a data point - I'm curious, if you see the same problem with xterm? It does hide the text cursor, but does it differently than the gnome terminal.

comment:4 Changed 15 months ago by JonAtFS

@janitor - yes, the same thing happens in xterm.

comment:5 Changed 15 months ago by JonAtFS

Some additional settings details for the guest VM.


  • Video Memory: 128 MB
  • Monitor Count: 1
  • Scale Factor: 100%
  • Graphics Controller: VMSVGA
  • Acceleration: 3D Acceleration enabled
  • Remote display and recording not enabled.


  • Shared Clipboard: Bidirectional
  • Drag'n'Drop: Bidirectional


  • 2 (of 4) CPUs assigned
  • Execution cap 100%
  • PAE/NX enabled
  • Nested VT-x/AM not enabled
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