[PATCH 1/2] allow wheel emulation to work even with absolute-position devices

[Dima Kogan]

Signed-off-by: Dima Kogan <dkogan at cds.caltech.edu>
---
 src/emuWheel.c |   22 +++++-----------------
 src/evdev.c    |   23 ++++++++++++++++++++---
 src/evdev.h    |    2 +-
 3 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/src/emuWheel.c b/src/emuWheel.c
index e7b2f98..734b11a 100644
--- a/src/emuWheel.c
+++ b/src/emuWheel.c
@@ -95,11 +95,10 @@ EvdevWheelEmuFilterButton(InputInfoPtr pInfo, unsigned int button, int value)
 
 /* Filter mouse wheel events */
 BOOL
-EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, struct input_event *pEv)
+EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, BOOL isX, int delta)
 {
     EvdevPtr pEvdev = (EvdevPtr)pInfo->private;
     WheelAxisPtr pAxis = NULL, pOtherAxis = NULL;
-    int value = pEv->value;
 
     /* Has wheel emulation been configured to be enabled? */
     if (!pEvdev->emulateWheel.enabled)
@@ -117,20 +116,12 @@ EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, struct input_event *pEv)
                 return TRUE;
         }
 
-	/* We don't want to intercept real mouse wheel events */
-	switch(pEv->code) {
-	case REL_X:
+	if (isX) {
 	    pAxis = &(pEvdev->emulateWheel.X);
 	    pOtherAxis = &(pEvdev->emulateWheel.Y);
-	    break;
-
-	case REL_Y:
+	} else {
 	    pAxis = &(pEvdev->emulateWheel.Y);
 	    pOtherAxis = &(pEvdev->emulateWheel.X);
-	    break;
-
-	default:
-	    break;
 	}
 
 	/* If we found REL_X or REL_Y, emulate a mouse wheel.
@@ -138,11 +129,8 @@ EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, struct input_event *pEv)
            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))
-		pOtherAxis->traveled_distance = 0;
-	}
+	if (EvdevWheelEmuInertia(pInfo, pAxis, delta))
+	    pOtherAxis->traveled_distance = 0;
 
 	/* Eat motion events while emulateWheel button pressed. */
 	return TRUE;
diff --git a/src/evdev.c b/src/evdev.c
index 81a0bd5..28358c6 100644
--- a/src/evdev.c
+++ b/src/evdev.c
@@ -497,8 +497,11 @@ EvdevProcessRelativeMotionEvent(InputInfoPtr pInfo, struct input_event *ev)
                 return;
 
             /* Handle mouse wheel emulation */
-            if (EvdevWheelEmuFilterMotion(pInfo, ev))
-                return;
+            if (ev->code == REL_X || ev->code == REL_Y)
+                if (EvdevWheelEmuFilterMotion(pInfo,
+                                              ev->code == REL_X,
+                                              ev->value))
+                    return;
 
             pEvdev->delta[ev->code] += value;
             break;
@@ -511,7 +514,7 @@ EvdevProcessRelativeMotionEvent(InputInfoPtr pInfo, struct input_event *ev)
 static void
 EvdevProcessAbsoluteMotionEvent(InputInfoPtr pInfo, struct input_event *ev)
 {
-    static int value;
+    static int value, oldValue;
     EvdevPtr pEvdev = pInfo->private;
 
     /* Get the signed value, earlier kernels had this as unsigned */
@@ -524,7 +527,21 @@ EvdevProcessAbsoluteMotionEvent(InputInfoPtr pInfo, struct input_event *ev)
     if (ev->code > ABS_MAX)
         return;
 
+    oldValue = pEvdev->vals[pEvdev->axis_map[ev->code]];
     pEvdev->vals[pEvdev->axis_map[ev->code]] = value;
+
+    /* Handle mouse wheel emulation */
+    /* If wheel emulation is active, I set pEvdev->vals[], but not
+       ev->code. This keeps track of the position so that the delta is
+       computed correctly, but does not update the cursor position in
+       the X-server */
+    if (ev->code == ABS_X || ev->code == ABS_Y) {
+        if(EvdevWheelEmuFilterMotion(pInfo,
+                                     ev->code == ABS_X,
+                                     value - oldValue))
+            return;
+    }
+
     if (ev->code == ABS_X)
         pEvdev->abs |= ABS_X_VALUE;
     else if (ev->code == ABS_Y)
diff --git a/src/evdev.h b/src/evdev.h
index 38adeaf..8799693 100644
--- a/src/evdev.h
+++ b/src/evdev.h
@@ -204,7 +204,7 @@ void EvdevMBEmuEnable(InputInfoPtr, BOOL);
 /* Mouse Wheel emulation */
 void EvdevWheelEmuPreInit(InputInfoPtr pInfo);
 BOOL EvdevWheelEmuFilterButton(InputInfoPtr pInfo, unsigned int button, int value);
-BOOL EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, struct input_event *pEv);
+BOOL EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, BOOL isX, int delta);
 
 /* Draglock code */
 void EvdevDragLockPreInit(InputInfoPtr pInfo);
-- 
1.6.5.2


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