Of course this only applies if you are using "evdev" as the mouse driver... could you post the full xorg-log (at least the parts related to the mouse pointer)?
$ grep -i mouse Xorg.0.log.old
(**) |-->Input Device "Mouse0"
(II) LoadModule: "mouse"
(II) Loading /usr/lib/xorg/modules/input//mouse_drv.so
(II) Module mouse: vendor="X.Org Foundation"
(==) NVIDIA(0): Silken mouse enabled
(**) Mouse0: Device: "/dev/input/mice"
(**) Mouse0: Protocol: "auto"
(**) Mouse0: always reports core events
(==) Mouse0: Emulate3Buttons, Emulate3Timeout: 50
(**) Mouse0: ZAxisMapping: buttons 4 and 5
(**) Mouse0: Buttons: 9
(**) Mouse0: Sensitivity: 1
(II) evaluating device (Mouse0)
(II) XINPUT: Adding extended input device "Mouse0" (type: MOUSE)
(--) Mouse0: PnP-detected protocol: "ExplorerPS/2"
(II) Mouse0: ps2EnableDataReporting: succeeded
(II) Mouse0: ps2EnableDataReporting: succeeded
(II) evaluating device (Mouse0)
(II) Mouse0: ps2EnableDataReporting: succeeded
(II) Mouse0: ps2EnableDataReporting: succeeded
Here is the related section in my xorg.conf :
Section "InputDevice"
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/input/mice"
Option "ZAxisMapping" "4 5"
EndSection
This issue occurs only when running sdlmame. I'll try to force protocol to IMPS/2 via device /dev/psaux.
I saw here
https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-input-evdev/+bug/97643, that specify
InputDevice "mouse" "SendCoreEvents"
in xorg.conf may help. But,I think it's already enabled by default like the log file says (**) Mouse0: always reports core events.