The “EmulateWheel”/“EmulateWheelButton” options are the wrong ones in this case IIUIC.
That would emulate a wheel, i.e. you press the mouse button and move the mouse, and programs will think you moved the mouse wheel.
See “man evdev” for details.
But I think this option would be the one the OP is looking for:
**Option "ButtonMapping" "string"
** Sets the button mapping for this device. The mapping is a space-
separated list of button mappings that correspond in order to
the physical buttons on the device (i.e. the first number is the
mapping for button 1, etc.). The default mapping is "1 2 3 ...
32". A mapping of 0 deactivates the button. Multiple buttons can
have the same mapping. For example, a left-handed mouse with
deactivated scroll-wheel would use a mapping of "3 2 1 0 0".
Invalid mappings are ignored and the default mapping is used.
Buttons not specified in the user's mapping use the default map-
Or, since this is about the middle mouse button, you could also use the “Emulate3Buttons” option. Then if you press the left and the right button at the same time, it is registered as the middle button.
Well, in 11-mouse.conf are settings specific to certain mice. You have to add the option to the right section for your mouse. (Xorg.0.log should tell which section is applied on your system, if any)
But I guess it would be better to add it to 10-evdev.conf, the section with
Identifier "evdev pointer catchall"
That one should be used in any case I think.
Or, even better, create a new file in /etc/X11/xorg.conf.d, but I can’t tell you how to do that correctly in this case.
I assume 10-evdev.conf is not the right place, since it should apply to a specific mouse and not to all.
I had a look in Xorg.0.log, but could’t guess from there which section to make the changes to if it concerns a bluetooth mouse (I have the problem on two computers)
on the desktop I identified the type via lsusb. but how can I identify for the bluetooth mouse?