Add support for high resolution wheel events from Linux 5.0+

They come in as a different relative axis, and we need to ignore the old
axis to not scroll double.

Change-Id: I808cce95417ec9f8058dee26d0a2694dda27944d
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

2 files changed, 36 insertions, 2 deletions

diff --git a/src/platformsupport/input/evdevmouse/qevdevmousehandler.cpp b/src/platformsupport/input/evdevmouse/qevdevmousehandler.cpp
index a729eeb851..0b1c5548c7 100644
--- a/src/platformsupport/input/evdevmouse/qevdevmousehandler.cpp
+++ b/src/platformsupport/input/evdevmouse/qevdevmousehandler.cpp
@@ -113,6 +113,8 @@ QEvdevMouseHandler::QEvdevMouseHandler(const QString &device, int fd, bool abs,
     if (m_abs)
         m_abs = getHardwareMaximum();
 
+    detectHiResWheelSupport();
+
     // socket notifier for events on the mouse device
     m_notify = new QSocketNotifier(m_fd, QSocketNotifier::Read, this);
     connect(m_notify, &QSocketNotifier::activated,
@@ -125,6 +127,25 @@ QEvdevMouseHandler::~QEvdevMouseHandler()
         qt_safe_close(m_fd);
 }
 
+void QEvdevMouseHandler::detectHiResWheelSupport()
+{
+#if defined(REL_WHEEL_HI_RES) || defined(REL_HWHEEL_HI_RES)
+    // Check if we can expect hires events as we will get both
+    // legacy and hires event and needs to know if we should
+    // ignore the legacy events.
+    unsigned char relFeatures[(REL_MAX / 8) + 1]{};
+    if (ioctl(m_fd, EVIOCGBIT(EV_REL, sizeof (relFeatures)), relFeatures) == -1)
+        return;
+
+#if defined(REL_WHEEL_HI_RES)
+    m_hiResWheel = TEST_BIT(relFeatures, REL_WHEEL_HI_RES);
+#endif
+#if defined(REL_HWHEEL_HI_RES)
+    m_hiResHWheel = TEST_BIT(relFeatures, REL_HWHEEL_HI_RES);
+#endif
+#endif
+}
+
 // Ask touch screen hardware for information on coordinate maximums
 // If any ioctls fail, revert to non abs mode
 bool QEvdevMouseHandler::getHardwareMaximum()
@@ -243,14 +264,24 @@ void QEvdevMouseHandler::readMouseData()
             } else if (data->code == REL_Y) {
                 m_y += data->value;
                 posChanged = true;
-            } else if (data->code == ABS_WHEEL) { // vertical scroll
+            } else if (!m_hiResWheel && data->code == REL_WHEEL) {
                 // data->value: positive == up, negative == down
                 delta.setY(120 * data->value);
                 emit handleWheelEvent(delta);
-            } else if (data->code == ABS_THROTTLE) { // horizontal scroll
+#ifdef REL_WHEEL_HI_RES
+            } else if (data->code == REL_WHEEL_HI_RES) {
+                delta.setY(data->value);
+                emit handleWheelEvent(delta);
+#endif
+            } else if (!m_hiResHWheel && data->code == REL_HWHEEL) {
                 // data->value: positive == right, negative == left
                 delta.setX(-120 * data->value);
                 emit handleWheelEvent(delta);
+#ifdef REL_HWHEEL_HI_RES
+            } else if (data->code == REL_HWHEEL_HI_RES) {
+                delta.setX(-data->value);
+                emit handleWheelEvent(delta);
+#endif
             }
         } else if (data->type == EV_KEY && data->code == BTN_TOUCH) {
             // We care about touchpads only, not touchscreens -> don't map to button press.
diff --git a/src/platformsupport/input/evdevmouse/qevdevmousehandler_p.h b/src/platformsupport/input/evdevmouse/qevdevmousehandler_p.h
index 93314e885f..8fcf49200b 100644
--- a/src/platformsupport/input/evdevmouse/qevdevmousehandler_p.h
+++ b/src/platformsupport/input/evdevmouse/qevdevmousehandler_p.h
@@ -81,6 +81,7 @@ private:
 
     void sendMouseEvent();
     bool getHardwareMaximum();
+    void detectHiResWheelSupport();
 
     QString m_device;
     int m_fd;
@@ -89,6 +90,8 @@ private:
     int m_prevx = 0, m_prevy = 0;
     bool m_abs;
     bool m_compression;
+    bool m_hiResWheel = false;
+    bool m_hiResHWheel = false;
     Qt::MouseButtons m_buttons;
     Qt::MouseButton m_button;
     QEvent::Type m_eventType;