Mouse works badly when connecting to host via vnc

[Askar Safin]

Let's assume we have some physical host A. This host runs qemu guest B locally without any options like "-vnc" etc.
Then I connect from some physical host C to the host A via VNC or Teamviewer ( www.teamviewer.com ). And then I try to remote control (via this vnc connection) qemu guest. But I cannot do this because my mouse disappears when I click at my qemu guest. I see little black square only. (This square is vnc feature, it automatically appears when mouse disappears.) When I click to some objects inside guest I will instead click to another random object inside guest.

I saw this bug in the following configurations:
* A: Debian squeeze 64-bit, Teamviewer 8, Qemu 1.1.2, C: Ubuntu precise 64-bit, Teamviewer 8, B: Windows 7 32-bit, command line:
qemu-system-x86_64 --enable-kvm -m 2048 -daemonize -localtime -drive cache=none,file=/root/vm/w7-sp1-i386-en.cow
* A: Debian squeeze 64-bit, Teamviewer 8, Qemu 1.1.2, C: Ubuntu precise 64-bit, Teamviewer 8, B: Debian squeeze 64-bit, command line:
qemu-system-x86_64 -enable-kvm -m 256 -daemonize -snapshot -net none -drive cache=none,file=/dev/sda
* A: Debian squeeze 64-bit, x11vnc 0.9.10, Qemu 1.1.2, C: Ubuntu precise 64-bit, xvnc4viewer 4.1.1, B: Windows 7 32-bit, command line:
qemu-system-x86_64 --enable-kvm -m 2048 -daemonize -localtime -drive cache=none,file=/root/vm/w7-sp1-i386-en.cow

Also, if I add "-usbdevice tablet" option, this bug will disappear. So, probably, this bug is not a bug. But in this case you should document it. I. e. you should add to docs something like "add -usbdevice tablet if you remote control qemu host".

Also, if I use "-vnc" option (in the text above I didn't use it!) my mouse doesn't work as expected, too. The pointers don't line up, i. e. are not synced. But if I add "-usbdevice tablet" option, mouse will work. As far as I know this is not a bug. But then document it, too. Qemu's man page already says "It is very useful to enable the usb tablet device when using this option (option -usbdevice tablet)" in qemu 1.1.2. But I think this is not enough. The man page should say: "You should add -usbdevice tablet option and your guest OS should support tablet device or your mouse will not work".

[Askar Safin (safinaskar)]

I tried to reproduce this bug using lastest stable version (1.4.0) and master (5e3a0f418c4d57399778cee0b55aebfb663b6425).
This versions seem to add "-usbdevice tablet" by default (and this is very good). But I think that if guest OS doesn't support tablet device then bug will still appear. So, I added option "-usbdevice mouse" to simulate this situation. And bug really appeared (i. e. mouse disappeared). So, please fix it or document it.

Configurations:
* A: Ubuntu precise 64-bit, x11vnc 0.9.12, Qemu 1.4.0, C: Debian squeeze 64-bit, xvnc4viewer 4.1.1, B: Ubuntu precise 64-bit, command line:
/opt/qemu-1.4.0/bin/qemu-system-x86_64 -enable-kvm -m 256 -daemonize -snapshot -drive cache=none,file=/dev/sda -net none -usbdevice mouse
* A: Ubuntu precise 64-bit, x11vnc 0.9.12, Qemu 5e3a0f418c4d57399778cee0b55aebfb663b6425, C: Debian squeeze 64-bit, xvnc4viewer 4.1.1, B: Ubuntu precise 64-bit, command line:
/opt/qemu-5e3a0f418c4d57399778cee0b55aebfb663b6425/bin/qemu-system-x86_64 -enable-kvm -m 256 -daemonize -snapshot -drive cache=none,file=/dev/sda -net none -usbdevice mouse

Same for -vnc option (i. e. pointers was not synced when using -usbdevice mouse)

[Thomas Huth (th-huth)]

As you mentioned already, the solution is to use an USB tablet instead of a mouse device, and as far as I can see, it is also mentioned in the documentation of the "-vnc" parameter, so I'm closing this ticket now...