xcb: Compress mouse motion and touch update events

The current version of the mouse motion event compression
algorithm does not work with certain configurations -
situations where we get one XCB_GE_GENERIC event between
every XCB_MOTION_NOTIFY event.

The new implementation tries to be less fragile. The
previous approach checked "is *the next* event the same
type as the current event", the new check asks "have
we buffered more events of the same type as the current
event". We buffer events of the same type only when the
main thread is unresponsive.

This patch adds event compression for XI_TouchUpdate in
addition to the fix for motion even compression.

Change-Id: Ie215eb5969e2060e463ebe48e3d3007390a30deb
Task-number: QTBUG-40889
Task-number: QTBUG-47069
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>

1 files changed, 59 insertions, 60 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp b/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
index 7a5480a8a5..e78ae8fa35 100644
--- a/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
@@ -459,82 +459,81 @@ static inline qreal fixed1616ToReal(FP1616 val)
 
 void QXcbConnection::xi2HandleEvent(xcb_ge_event_t *event)
 {
-    if (xi2PrepareXIGenericDeviceEvent(event, m_xiOpCode)) {
-        xXIGenericDeviceEvent *xiEvent = reinterpret_cast<xXIGenericDeviceEvent *>(event);
-        int sourceDeviceId = xiEvent->deviceid; // may be the master id
-        xXIDeviceEvent *xiDeviceEvent = 0;
-        QXcbWindowEventListener *eventListener = 0;
+    xi2PrepareXIGenericDeviceEvent(event);
+    xXIGenericDeviceEvent *xiEvent = reinterpret_cast<xXIGenericDeviceEvent *>(event);
+    int sourceDeviceId = xiEvent->deviceid; // may be the master id
+    xXIDeviceEvent *xiDeviceEvent = 0;
+    QXcbWindowEventListener *eventListener = 0;
 
-        switch (xiEvent->evtype) {
-        case XI_ButtonPress:
-        case XI_ButtonRelease:
-        case XI_Motion:
+    switch (xiEvent->evtype) {
+    case XI_ButtonPress:
+    case XI_ButtonRelease:
+    case XI_Motion:
 #ifdef XCB_USE_XINPUT22
-        case XI_TouchBegin:
-        case XI_TouchUpdate:
-        case XI_TouchEnd:
+    case XI_TouchBegin:
+    case XI_TouchUpdate:
+    case XI_TouchEnd:
 #endif
-        {
-            xiDeviceEvent = reinterpret_cast<xXIDeviceEvent *>(event);
-            eventListener = windowEventListenerFromId(xiDeviceEvent->event);
-            if (eventListener) {
-                long result = 0;
-                if (eventListener->handleGenericEvent(reinterpret_cast<xcb_generic_event_t *>(event), &result))
-                    return;
-            }
-            sourceDeviceId = xiDeviceEvent->sourceid; // use the actual device id instead of the master
-            break;
-        }
-        case XI_HierarchyChanged:
-            xi2HandleHierachyEvent(xiEvent);
-            return;
-        case XI_DeviceChanged:
-            xi2HandleDeviceChangedEvent(xiEvent);
-            return;
-        default:
-            break;
+    {
+        xiDeviceEvent = reinterpret_cast<xXIDeviceEvent *>(event);
+        eventListener = windowEventListenerFromId(xiDeviceEvent->event);
+        if (eventListener) {
+            long result = 0;
+            if (eventListener->handleGenericEvent(reinterpret_cast<xcb_generic_event_t *>(event), &result))
+                return;
         }
+        sourceDeviceId = xiDeviceEvent->sourceid; // use the actual device id instead of the master
+        break;
+    }
+    case XI_HierarchyChanged:
+        xi2HandleHierachyEvent(xiEvent);
+        return;
+    case XI_DeviceChanged:
+        xi2HandleDeviceChangedEvent(xiEvent);
+        return;
+    default:
+        break;
+    }
 
 #ifndef QT_NO_TABLETEVENT
-        for (int i = 0; i < m_tabletData.count(); ++i) {
-            if (m_tabletData.at(i).deviceId == sourceDeviceId) {
-                if (xi2HandleTabletEvent(xiEvent, &m_tabletData[i], eventListener))
-                    return;
-            }
+    for (int i = 0; i < m_tabletData.count(); ++i) {
+        if (m_tabletData.at(i).deviceId == sourceDeviceId) {
+            if (xi2HandleTabletEvent(xiEvent, &m_tabletData[i], eventListener))
+                return;
         }
+    }
 #endif // QT_NO_TABLETEVENT
 
 #ifdef XCB_USE_XINPUT21
-        QHash<int, ScrollingDevice>::iterator device = m_scrollingDevices.find(sourceDeviceId);
-        if (device != m_scrollingDevices.end())
-            xi2HandleScrollEvent(xiEvent, device.value());
+    QHash<int, ScrollingDevice>::iterator device = m_scrollingDevices.find(sourceDeviceId);
+    if (device != m_scrollingDevices.end())
+        xi2HandleScrollEvent(xiEvent, device.value());
 #endif // XCB_USE_XINPUT21
 
 #ifdef XCB_USE_XINPUT22
-        if (xiDeviceEvent) {
-            switch (xiDeviceEvent->evtype) {
-            case XI_ButtonPress:
-            case XI_ButtonRelease:
-            case XI_Motion:
-                if (xi2MouseEvents() && eventListener && !(xiDeviceEvent->flags & XIPointerEmulated))
-                    eventListener->handleXIMouseEvent(event);
-                break;
+    if (xiDeviceEvent) {
+        switch (xiDeviceEvent->evtype) {
+        case XI_ButtonPress:
+        case XI_ButtonRelease:
+        case XI_Motion:
+            if (xi2MouseEvents() && eventListener && !(xiDeviceEvent->flags & XIPointerEmulated))
+                eventListener->handleXIMouseEvent(event);
+            break;
 
-            case XI_TouchBegin:
-            case XI_TouchUpdate:
-            case XI_TouchEnd:
-                if (Q_UNLIKELY(lcQpaXInput().isDebugEnabled()))
-                    qCDebug(lcQpaXInput, "XI2 touch event type %d seq %d detail %d pos %6.1f, %6.1f root pos %6.1f, %6.1f on window %x",
-                            event->event_type, xiDeviceEvent->sequenceNumber, xiDeviceEvent->detail,
-                            fixed1616ToReal(xiDeviceEvent->event_x), fixed1616ToReal(xiDeviceEvent->event_y),
-                            fixed1616ToReal(xiDeviceEvent->root_x), fixed1616ToReal(xiDeviceEvent->root_y),xiDeviceEvent->event);
-                if (QXcbWindow *platformWindow = platformWindowFromId(xiDeviceEvent->event))
-                    xi2ProcessTouch(xiDeviceEvent, platformWindow);
-                break;
-            }
+        case XI_TouchBegin:
+        case XI_TouchUpdate:
+        case XI_TouchEnd:
+            if (Q_UNLIKELY(lcQpaXInput().isDebugEnabled()))
+                qCDebug(lcQpaXInput, "XI2 touch event type %d seq %d detail %d pos %6.1f, %6.1f root pos %6.1f, %6.1f on window %x",
+                        event->event_type, xiDeviceEvent->sequenceNumber, xiDeviceEvent->detail,
+                        fixed1616ToReal(xiDeviceEvent->event_x), fixed1616ToReal(xiDeviceEvent->event_y),
+                        fixed1616ToReal(xiDeviceEvent->root_x), fixed1616ToReal(xiDeviceEvent->root_y),xiDeviceEvent->event);
+            if (QXcbWindow *platformWindow = platformWindowFromId(xiDeviceEvent->event))
+                xi2ProcessTouch(xiDeviceEvent, platformWindow);
+            break;
         }
-#endif // XCB_USE_XINPUT22
     }
+#endif // XCB_USE_XINPUT22
 }
 
 #ifdef XCB_USE_XINPUT22