Fix wheel emulation for absolute device (#68415)

wheel emulation, for some reasons beyond time, got the value from
pEvdev->vals, then set the value back into pEvdev->vals. Alas, that value is
always 0, hence oldValue is zero and the delta is nil.

If we're not in relative (touchpad) mode, store the current value in
old_vals, so they're retrievable for the next event.

X.Org Bug 68415 <http://bugs.freedesktop.org/show_bug.cgi?id=68415>

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
(cherry picked from commit f6fcad8b107e834e26fb3da2c89e05294ff0a74c)

2 files changed, 37 insertions, 26 deletions

diff --git a/src/emuWheel.c b/src/emuWheel.c
index 81b777f..857f029 100644
--- a/src/emuWheel.c
+++ b/src/emuWheel.c
@@ -97,7 +97,6 @@ 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)
@@ -118,9 +117,13 @@ EvdevWheelEmuFilterMotion(InputInfoPtr pInfo, struct input_event *pEv)
 	/* We don't want to intercept real mouse wheel events */
 	if(pEv->type == EV_ABS) {
 	    int axis = pEvdev->abs_axis_map[pEv->code];
-	    oldValue = valuator_mask_get(pEvdev->vals, axis);
-	    valuator_mask_set(pEvdev->vals, axis, value);
-	    value -= oldValue; /* make value into a differential measurement */
+	    int oldValue;
+
+	    if (axis > -1 && valuator_mask_fetch(pEvdev->old_vals, axis, &oldValue)) {
+		valuator_mask_set(pEvdev->vals, axis, value);
+		value -= oldValue; /* make value into a differential measurement */
+	    } else
+                value = 0; /* avoid a jump on the first touch */
 	}
 
 	switch(pEv->code) {
diff --git a/src/evdev.c b/src/evdev.c
index af4aba3..16a0358 100644
--- a/src/evdev.c
+++ b/src/evdev.c
@@ -493,31 +493,39 @@ EvdevProcessValuators(InputInfoPtr pInfo)
     EvdevPtr pEvdev = pInfo->private;
     int *delta = pEvdev->delta;
 
-    /* convert to relative motion for touchpads */
-    if (pEvdev->abs_queued && (pEvdev->flags & EVDEV_RELATIVE_MODE)) {
-        if (pEvdev->in_proximity) {
-            if (valuator_mask_isset(pEvdev->vals, 0))
-            {
-                if (valuator_mask_isset(pEvdev->old_vals, 0))
-                    delta[REL_X] = valuator_mask_get(pEvdev->vals, 0) -
-                                   valuator_mask_get(pEvdev->old_vals, 0);
-                valuator_mask_set(pEvdev->old_vals, 0,
-                                  valuator_mask_get(pEvdev->vals, 0));
-            }
-            if (valuator_mask_isset(pEvdev->vals, 1))
-            {
-                if (valuator_mask_isset(pEvdev->old_vals, 1))
-                    delta[REL_Y] = valuator_mask_get(pEvdev->vals, 1) -
-                                   valuator_mask_get(pEvdev->old_vals, 1);
-                valuator_mask_set(pEvdev->old_vals, 1,
-                                  valuator_mask_get(pEvdev->vals, 1));
+    if (pEvdev->abs_queued) {
+        /* convert to relative motion for touchpads */
+        if (pEvdev->flags & EVDEV_RELATIVE_MODE) {
+            if (pEvdev->in_proximity) {
+                if (valuator_mask_isset(pEvdev->vals, 0))
+                {
+                    if (valuator_mask_isset(pEvdev->old_vals, 0))
+                        delta[REL_X] = valuator_mask_get(pEvdev->vals, 0) -
+                            valuator_mask_get(pEvdev->old_vals, 0);
+                    valuator_mask_set(pEvdev->old_vals, 0,
+                            valuator_mask_get(pEvdev->vals, 0));
+                }
+                if (valuator_mask_isset(pEvdev->vals, 1))
+                {
+                    if (valuator_mask_isset(pEvdev->old_vals, 1))
+                        delta[REL_Y] = valuator_mask_get(pEvdev->vals, 1) -
+                            valuator_mask_get(pEvdev->old_vals, 1);
+                    valuator_mask_set(pEvdev->old_vals, 1,
+                            valuator_mask_get(pEvdev->vals, 1));
+                }
+            } else {
+                valuator_mask_zero(pEvdev->old_vals);
             }
+            valuator_mask_zero(pEvdev->vals);
+            pEvdev->abs_queued = 0;
+            pEvdev->rel_queued = 1;
         } else {
-            valuator_mask_zero(pEvdev->old_vals);
+            int val;
+            if (valuator_mask_fetch(pEvdev->vals, 0, &val))
+                valuator_mask_set(pEvdev->old_vals, 0, val);
+            if (valuator_mask_fetch(pEvdev->vals, 1, &val))
+                valuator_mask_set(pEvdev->old_vals, 1, val);
         }
-        valuator_mask_zero(pEvdev->vals);
-        pEvdev->abs_queued = 0;
-        pEvdev->rel_queued = 1;
     }
 
     if (pEvdev->rel_queued) {