xcb: Ignore XI2 LMB mouse events from touch screens

157ee01a8d was trying to
minimize some side effects of the bug in the evdev driver
(https://bugs.freedesktop.org/show_bug.cgi?id=98188) by
not changing mouse button state on motion.
Unfortunately it resurrected bugs that were fixed by
76de1ac0a4.
Filter out mouse events from touch screens instead.
This change reverts 157ee01a8d.

Task-number: QTBUG-32609
Task-number: QTBUG-35065
Task-number: QTBUG-43776
Task-number: QTBUG-44166
Task-number: QTBUG-44231
Task-number: QTBUG-56156
Change-Id: Ie17710d94beabeb08681d669a9d8309be9b44e73
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/plugins/platforms/xcb/qxcbconnection.h

@@ -517,6 +517,7 @@ public:
 
 #ifdef XCB_USE_XINPUT22
     bool xi2MouseEvents() const;
+    bool isTouchScreen(int id) const;
 #endif
 
 protected:

src/plugins/platforms/xcb/qxcbconnection_xi2.cpp

@@ -1025,6 +1025,13 @@ Qt::MouseButton QXcbConnection::xiToQtMouseButton(uint32_t b)
     return Qt::NoButton;
 }
 
+bool QXcbConnection::isTouchScreen(int id) const
+{
+    auto device = m_touchDevices.value(id);
+    return device && device->qtTouchDevice
+        && device->qtTouchDevice->type() == QTouchDevice::TouchScreen;
+}
+
 static QTabletEvent::TabletDevice toolIdToTabletDevice(quint32 toolId) {
     // keep in sync with wacom_intuos_inout() in Linux kernel driver wacom_wac.c
     switch (toolId) {

src/plugins/platforms/xcb/qxcbwindow.cpp

@@ -2423,22 +2423,27 @@ static inline int fixed1616ToInt(FP1616 val)
     return int((qreal(val >> 16)) + (val & 0xFFFF) / (qreal)0xFFFF);
 }
 
-void QXcbWindow::handleXIMouseButtonState(const xcb_ge_event_t *event)
-{
-    QXcbConnection *conn = connection();
-    const xXIDeviceEvent *ev = reinterpret_cast<const xXIDeviceEvent *>(event);
-    if (ev->buttons_len > 0) {
-        unsigned char *buttonMask = (unsigned char *) &ev[1];
-        for (int i = 1; i <= 15; ++i)
-            conn->setButton(conn->translateMouseButton(i), XIMaskIsSet(buttonMask, i));
-    }
-}
-
 // With XI 2.2+ press/release/motion comes here instead of the above handlers.
 void QXcbWindow::handleXIMouseEvent(xcb_ge_event_t *event, Qt::MouseEventSource source)
 {
     QXcbConnection *conn = connection();
     xXIDeviceEvent *ev = reinterpret_cast<xXIDeviceEvent *>(event);
+
+    if (ev->buttons_len > 0) {
+        unsigned char *buttonMask = (unsigned char *) &ev[1];
+        // There is a bug in the evdev driver which leads to receiving mouse events without
+        // XIPointerEmulated being set: https://bugs.freedesktop.org/show_bug.cgi?id=98188
+        // Filter them out by other attributes: when their source device is a touch screen
+        // and the LMB is pressed.
+        if (XIMaskIsSet(buttonMask, 1) && conn->isTouchScreen(ev->sourceid)) {
+            if (Q_UNLIKELY(lcQpaXInputEvents().isDebugEnabled()))
+                qCDebug(lcQpaXInput, "XI2 mouse event from touch device %d was ignored", ev->sourceid);
+            return;
+        }
+        for (int i = 1; i <= 15; ++i)
+            conn->setButton(conn->translateMouseButton(i), XIMaskIsSet(buttonMask, i));
+    }
+
     const Qt::KeyboardModifiers modifiers = conn->keyboard()->translateModifiers(ev->mods.effective_mods);
     const int event_x = fixed1616ToInt(ev->event_x);
     const int event_y = fixed1616ToInt(ev->event_y);
@@ -2458,23 +2463,18 @@ void QXcbWindow::handleXIMouseEvent(xcb_ge_event_t *event, Qt::MouseEventSource
 
     switch (ev->evtype) {
     case XI_ButtonPress:
-        handleXIMouseButtonState(event);
         if (Q_UNLIKELY(lcQpaXInputEvents().isDebugEnabled()))
             qCDebug(lcQpaXInputEvents, "XI2 mouse press, button %d, time %d, source %s", button, ev->time, sourceName);
         conn->setButton(button, true);
         handleButtonPressEvent(event_x, event_y, root_x, root_y, ev->detail, modifiers, ev->time, source);
         break;
     case XI_ButtonRelease:
-        handleXIMouseButtonState(event);
         if (Q_UNLIKELY(lcQpaXInputEvents().isDebugEnabled()))
             qCDebug(lcQpaXInputEvents, "XI2 mouse release, button %d, time %d, source %s", button, ev->time, sourceName);
         conn->setButton(button, false);
         handleButtonReleaseEvent(event_x, event_y, root_x, root_y, ev->detail, modifiers, ev->time, source);
         break;
     case XI_Motion:
-        // Here we do NOT call handleXIMouseButtonState because we don't expect button state change to be bundled with motion.
-        // When a touchscreen is pressed, an XI_Motion event occurs in which XIMaskIsSet says the left button is pressed,
-        // but we don't want QGuiApplicationPrivate::processMouseEvent() to react by generating a mouse press event.
         if (Q_UNLIKELY(lcQpaXInputEvents().isDebugEnabled()))
             qCDebug(lcQpaXInputEvents, "XI2 mouse motion %d,%d, time %d, source %s", event_x, event_y, ev->time, sourceName);
         handleMotionNotifyEvent(event_x, event_y, root_x, root_y, modifiers, ev->time, source);

src/plugins/platforms/xcb/qxcbwindow.h

@@ -139,7 +139,6 @@ public:
     void handleFocusOutEvent(const xcb_focus_out_event_t *event) override;
     void handlePropertyNotifyEvent(const xcb_property_notify_event_t *event) override;
 #ifdef XCB_USE_XINPUT22
-    void handleXIMouseButtonState(const xcb_ge_event_t *);
     void handleXIMouseEvent(xcb_ge_event_t *, Qt::MouseEventSource source = Qt::MouseEventNotSynthesized) override;
     void handleXIEnterLeave(xcb_ge_event_t *) override;
 #endif