[PATCH] evdev: allow mouse wheel emulation to work even with absolute-position devices (like touchscreens)

[Peter Hutterer]

On Sun, Dec 06, 2009 at 11:42:25PM -0800, Dima Kogan wrote:
> OK, here's the new patch. Much smaller now. There's some spaces-vs-tabs
> inconsistency in emuWheel.c, and it took me a few tries to make sure
> that this patch wasn't touching those. Might make sense to do another
> patch to clean up the whitespace.

yeah, it's supposed to be 4 spaces, indent, no tabs. I haven't been
checking enough though. not sure if a patch fixing those is really worth the
effort, this code doesn't see that much change, so I'd rather have a
convenient blame if needed.

> On Mon, 7 Dec 2009 12:36:54 +1000
> Peter Hutterer <peter.hutterer at who-t.net> wrote:
> 
> > On Sun, Dec 06, 2009 at 06:23:28PM -0800, Dima Kogan wrote:
> > > Hi Peter.
> > > 
> > > I specifically didn't do it that way because I didn't want to assume
> > > that REL_X == ABS_X and REL_Y == ABS_Y. I don't know how set in
> > > stone those definitions are. I'd like you to confirm that this
> > > assumption will hold for the foreseeable future, and if so, I will
> > > redo the patch. Let me know. Thanks.
> > 
> > pretty much set in stone. if the kernel changes the definitions for
> > those, a lot of things will break.
> > of course, you could do #if trickery for the case but let's not worry
> > about it.
> > 
> > Cheers,
> >   Peter

> From 0dbf72dfdf7ff6acedb8315a79c52535c5cad754 Mon Sep 17 00:00:00 2001
> From: Dima Kogan <dkogan at cds.caltech.edu>
> Date: Sat, 5 Dec 2009 02:05:19 -0800
> Subject: [PATCH] allow wheel emulation to work with absolute-position devices
> 
> Signed-off-by: Dima Kogan <dkogan at cds.caltech.edu>
> ---
>  src/emuWheel.c |   20 +++++++++++++++-----
>  src/evdev.c    |    3 +++
>  2 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/src/emuWheel.c b/src/emuWheel.c
> index e7b2f98..b644d66 100644
> --- a/src/emuWheel.c
> +++ b/src/emuWheel.c
> @@ -100,6 +100,7 @@ EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, struct input_event *pEv)
>      EvdevPtr pEvdev = (EvdevPtr)pInfo->private;
>      WheelAxisPtr pAxis = NULL, pOtherAxis = NULL;
>      int value = pEv->value;
> +    int oldValue;
>  
>      /* Has wheel emulation been configured to be enabled? */
>      if (!pEvdev->emulateWheel.enabled)
> @@ -118,12 +119,21 @@ EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, struct input_event *pEv)
>          }
>  
>  	/* We don't want to intercept real mouse wheel events */
> +	if(pEv->type == EV_ABS) {
> +	    oldValue = pEvdev->vals[pEvdev->axis_map[pEv->code]];
> +	    pEvdev->vals[pEvdev->axis_map[pEv->code]] = value;
> +	    value -= oldValue; // make value into a differential measurement
> +	}
> +
>  	switch(pEv->code) {
> +
> +	// ABS_X has the same value as REL_X, so this case catches both
>  	case REL_X:
>  	    pAxis = &(pEvdev->emulateWheel.X);
>  	    pOtherAxis = &(pEvdev->emulateWheel.Y);
>  	    break;
>  
> +	// ABS_Y has the same value as REL_Y, so this case catches both
>  	case REL_Y:
>  	    pAxis = &(pEvdev->emulateWheel.Y);
>  	    pOtherAxis = &(pEvdev->emulateWheel.X);
> @@ -133,11 +143,11 @@ EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, struct input_event *pEv)
>  	    break;
>  	}
>  
> -	/* If we found REL_X or REL_Y, emulate a mouse wheel.
> -           Reset the inertia of the other axis when a scroll event was sent
> -           to avoid the buildup of erroneous scroll events if the user
> -           doesn't move in a perfectly straight line.
> -         */
> +	/* If we found REL_X, REL_Y, ABS_X or ABS_Y then emulate a mouse
> +	   wheel.  Reset the inertia of the other axis when a scroll event
> +	   was sent to avoid the buildup of erroneous scroll events if the
> +	   user doesn't move in a perfectly straight line.
> +	 */
>  	if (pAxis)
>  	{
>  	    if (EvdevWheelEmuInertia(pInfo, pAxis, value))
> diff --git a/src/evdev.c b/src/evdev.c
> index 81a0bd5..1e0f9e2 100644
> --- a/src/evdev.c
> +++ b/src/evdev.c
> @@ -524,6 +524,9 @@ EvdevProcessAbsoluteMotionEvent(InputInfoPtr pInfo, struct input_event *ev)
>      if (ev->code > ABS_MAX)
>          return;
>  
> +    if (EvdevWheelEmuFilterMotion(pInfo, ev))
> +        return;
> +
>      pEvdev->vals[pEvdev->axis_map[ev->code]] = value;
>      if (ev->code == ABS_X)
>          pEvdev->abs |= ABS_X_VALUE;
> -- 
> 1.6.5.2

applied, thanks. I changed the // comments to /* */ style comments though.

Cheers,
  Peter