Bug#684051: xserver-xorg-core: Vertical scrolling with emulated mouse wheel stopped working

[deb.tno@xoxy.net]

On [Mon, 06.08.2012 17:32], Julien Cristau - jcristau@debian.org wrote:
> On Mon, Aug  6, 2012 at 16:23:28 +0200, Arne Steffens wrote:
> 
> > 
> > upgrading from xserver-xorg-core-1.12.1.902-1 to
> > xserver-xorg-core-1.12.3-1 caused X to no longer register vertical
> > scrolling using an emulated mouse wheel. Horizontal scrolling still
> > works.  xev shows no events for vertical scrolling (mouse button 4 and
> > 5). 
> > If I downgrade back to xserver-xorg-core-1.12.1.902-1 vertical
> > scrolling works again. 
> > 
> What's an emulated mouse wheel?
> 
> Cheers,
> Julien

Think of it as something similar to an emulated 3rd button, only more
complicated. ;)
Basicly you define one mouse button using this code in the right
InputClass section in /etc/X11/xorg.conf like this

--snip--
Option "EmulateWheel" "true"
Option "EmulateWheelButton" "8"

Option "ZAxisMapping" "4 5 6 7"
Option "YAxisMapping" "4 5"
Option "XAxisMapping" "6 7"

--snip--


If you hold this button (in my case button 8) pressed and move the mouse
in a direction, it will not move the mouse pointer but generate
corresponding button events. If the mouse is moved a longer distance,
more events are generated. 

Example: Holding button 8 and moving the mouse left will generate
several ButtonPressed and ButtonReleased events for button 6,
effectively scrolling left. Same for right, up and down.

I guess this sounds rather stupid if you are really using a mouse. It's
way more useful if you are using a trackball or a trackpoint.

Best wishes
Arne