Fix a Qt scrolling bug, don't reset the valuator on slave switch

0001-dix-leave-last.valuators-alone-on-slave-switch.patch

@@ -0,0 +1,89 @@
+From 13f9b07039484927532d913dbccc664679235bf6 Mon Sep 17 00:00:00 2001
+From: Peter Hutterer <peter.hutterer@who-t.net>
+Date: Mon, 25 Mar 2019 13:19:41 +1000
+Subject: [PATCH xserver] dix: leave last.valuators alone on slave switch
+
+Terms:
+dev->last.valuator[] is the last value given to us by the driver
+dev->valuator.axisVal[] is the last value sent to the client
+dev->last.scroll[] is the abs value of the scroll axis as given by the driver,
+        used for button emulation calculation (and the remainder)
+
+This function updates the device's last.valuator state based on the current
+master axis state. This way, relative motion continues fluidly when switching
+between devices. Before mouse 2 comes into effect, it's valuator state is
+updated to wherever the pointer currently is so the relative event applies on
+top of that.
+
+This can only work for x/y axes, all other axes aren't guaranteed to have the
+same meaning and/or may not be present:
+- xtest device: no valuator 2
+- mouse: valuator 2 is horizontal scroll axis
+- tablet: valuator 2 is pressure
+
+Scaling the current value from the pressure range into the range for
+horizontal scrolling makes no sense. And it causes scroll jumps:
+
+- scroll down, last.valuator == axisVal == 20
+- xdotool click 1, the XTest device doesn't have that valuator
+- scroll up
+  - updateSlaveDeviceCoords reset last.valuator to 0 (axisVal == 20)
+  - DeviceClassesChangedEvent includes value 20 for the axis
+  - event is processed, last.value changes from 0 to -1
+  - axisVal is updated to -1, causing a jump of -21
+
+The same applies when we switch from tablet to mouse wheel if the pressure
+value is 0 on proximity out (basically guaranteed). So let's drop this code
+altogether and only leave the scaling for the relative x/y motion.
+
+Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
+---
+ dix/getevents.c | 25 +------------------------
+ 1 file changed, 1 insertion(+), 24 deletions(-)
+
+diff --git a/dix/getevents.c b/dix/getevents.c
+index d8955969a..f83dac709 100644
+--- a/dix/getevents.c
++++ b/dix/getevents.c
+@@ -331,9 +331,6 @@ rescaleValuatorAxis(double coord, AxisInfoPtr from, AxisInfoPtr to,
+ static void
+ updateSlaveDeviceCoords(DeviceIntPtr master, DeviceIntPtr pDev)
+ {
+-    int i;
+-    DeviceIntPtr lastSlave;
+-
+     /* master->last.valuators[0]/[1] is in desktop-wide coords and the actual
+      * position of the pointer */
+     pDev->last.valuators[0] = master->last.valuators[0];
+@@ -358,27 +355,7 @@ updateSlaveDeviceCoords(DeviceIntPtr master, DeviceIntPtr pDev)
+                                                       screenInfo.height);
+     }
+ 
+-    /* calculate the other axis as well based on info from the old
+-     * slave-device. If the old slave had less axes than this one,
+-     * last.valuators is reset to 0.
+-     */
+-    if ((lastSlave = master->last.slave) && lastSlave->valuator) {
+-        for (i = 2; i < pDev->valuator->numAxes; i++) {
+-            if (i >= lastSlave->valuator->numAxes) {
+-                pDev->last.valuators[i] = 0;
+-                valuator_mask_set_double(pDev->last.scroll, i, 0);
+-            }
+-            else {
+-                double val = pDev->last.valuators[i];
+-
+-                val = rescaleValuatorAxis(val, lastSlave->valuator->axes + i,
+-                                          pDev->valuator->axes + i, 0, 0);
+-                pDev->last.valuators[i] = val;
+-                valuator_mask_set_double(pDev->last.scroll, i, val);
+-            }
+-        }
+-    }
+-
++    /* other axes are left as-is */
+ }
+ 
+ /**
+-- 
+2.20.1
+

xorg-x11-server.spec

@@ -46,7 +46,7 @@
 Summary:   X.Org X11 X server
 Name:      xorg-x11-server
 Version:   1.20.4
-Release:   2%{?gitdate:.%{gitdate}}%{?dist}
+Release:   3%{?gitdate:.%{gitdate}}%{?dist}
 URL:       http://www.x.org
 License:   MIT
 
@@ -96,6 +96,9 @@ Patch6: 0001-Fedora-hack-Make-the-suid-root-wrapper-always-start-.patch
 
 Patch10: 0001-xwayland-present-Destroy-sync_callback-in-xwl_presen.patch
 
+# https://gitlab.freedesktop.org/xorg/xserver/merge_requests/152
+Patch11: 0001-dix-leave-last.valuators-alone-on-slave-switch.patch
+
 BuildRequires: systemtap-sdt-devel
 BuildRequires: git
 BuildRequires: automake autoconf libtool pkgconfig
@@ -520,6 +523,9 @@ find %{inst_srcdir}/hw/xfree86 -name \*.c -delete
 
 
 %changelog
+* Wed Mar 27 2019 Peter Hutterer <peter.hutterer@redhat.com> 1.20.4-3
+- Fix a Qt scrolling bug, don't reset the valuator on slave switch
+
 * Thu Mar 21 2019 Adam Jackson <ajax@redhat.com> - 1.20.4-2
 - Backport an Xwayland crash fix in the Present code