[PATCH] allow wheel emulation to work with absolute-position devices

[Dima Kogan]

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


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