wayland: Fix handling of synthetic touch cancel events

In case the compositor wants to cancel a touch sequence, we need to
ignore subsequent touch motion and touch up events until a new sequence
is initiated by the user.

Previously, it was implicitly handled by clearing the mapping table
between the touch slots and touch ids generated by kwayland-server.

autotests/integration/touch_input_test.cpp

@@ -275,8 +275,6 @@ void TouchInputTest::testTouchPointCount()
     kwinApp()->platform()->touchUp(1, timestamp++);
     QCOMPARE(kwinApp()->platform()->touchPointCount(), 2);
 
-    kwinApp()->platform()->cancelTouchSequence();
-    QCOMPARE(kwinApp()->platform()->touchPointCount(), 1);
     kwinApp()->platform()->cancelTouchSequence();
     QCOMPARE(kwinApp()->platform()->touchPointCount(), 0);
 }

src/input.cpp

@@ -2303,7 +2303,7 @@ void InputRedirection::setupLibInput()
         connect(conn, &LibInput::Connection::touchDown, m_touch, &TouchInputRedirection::processDown);
         connect(conn, &LibInput::Connection::touchUp, m_touch, &TouchInputRedirection::processUp);
         connect(conn, &LibInput::Connection::touchMotion, m_touch, &TouchInputRedirection::processMotion);
-        connect(conn, &LibInput::Connection::touchCanceled, m_touch, &TouchInputRedirection::processCancel);
+        connect(conn, &LibInput::Connection::touchCanceled, m_touch, &TouchInputRedirection::cancel);
         connect(conn, &LibInput::Connection::touchFrame, m_touch, &TouchInputRedirection::frame);
         auto handleSwitchEvent = [this] (SwitchEvent::State state, quint32 time, quint64 timeMicroseconds, LibInput::Device *device) {
             SwitchEvent event(state, time, timeMicroseconds, device);
@@ -2496,7 +2496,7 @@ void InputRedirection::processTouchMotion(qint32 id, const QPointF &pos, quint32
 
 void InputRedirection::cancelTouchSequence()
 {
-    m_touch->processCancel();
+    m_touch->cancel();
 }
 
 void InputRedirection::cancelTouch()

src/touch_input.cpp

@@ -66,7 +66,7 @@ bool TouchInputRedirection::focusUpdatesBlocked()
     if (waylandServer()->seat()->isDragTouch()) {
         return true;
     }
-    if (m_touches > 1) {
+    if (m_activeTouchPoints.count() > 1) {
         // first touch defines focus
         return true;
     }
@@ -75,9 +75,8 @@ bool TouchInputRedirection::focusUpdatesBlocked()
 
 bool TouchInputRedirection::positionValid() const
 {
-    Q_ASSERT(m_touches >= 0);
     // we can only determine a position with at least one touch point
-    return m_touches;
+    return !m_activeTouchPoints.isEmpty();
 }
 
 void TouchInputRedirection::focusUpdate(Toplevel *focusOld, Toplevel *focusNow)
@@ -144,8 +143,8 @@ void TouchInputRedirection::processDown(qint32 id, const QPointF &pos, quint32 t
     }
     m_lastPosition = pos;
     m_windowUpdatedInCycle = false;
-    m_touches++;
+    m_activeTouchPoints.insert(id);
-    if (m_touches == 1) {
+    if (m_activeTouchPoints.count() == 1) {
         update();
     }
     input()->processSpies(std::bind(&InputEventSpy::touchDown, std::placeholders::_1, id, pos, time));
@@ -159,12 +158,14 @@ void TouchInputRedirection::processUp(qint32 id, quint32 time, LibInput::Device
     if (!inited()) {
         return;
     }
+    if (!m_activeTouchPoints.remove(id)) {
+        return;
+    }
     m_windowUpdatedInCycle = false;
     input()->processSpies(std::bind(&InputEventSpy::touchUp, std::placeholders::_1, id, time));
     input()->processFilters(std::bind(&InputEventFilter::touchUp, std::placeholders::_1, id, time));
     m_windowUpdatedInCycle = false;
-    m_touches--;
+    if (m_activeTouchPoints.count() == 0) {
-    if (m_touches == 0) {
         update();
     }
 }
@@ -175,6 +176,9 @@ void TouchInputRedirection::processMotion(qint32 id, const QPointF &pos, quint32
     if (!inited()) {
         return;
     }
+    if (!m_activeTouchPoints.contains(id)) {
+        return;
+    }
     m_lastPosition = pos;
     m_windowUpdatedInCycle = false;
     input()->processSpies(std::bind(&InputEventSpy::touchMotion, std::placeholders::_1, id, pos, time));
@@ -182,17 +186,16 @@ void TouchInputRedirection::processMotion(qint32 id, const QPointF &pos, quint32
     m_windowUpdatedInCycle = false;
 }
 
-void TouchInputRedirection::processCancel()
-{
-    m_touches--;
-    cancel();
-}
-
 void TouchInputRedirection::cancel()
 {
     if (!inited()) {
         return;
     }
+    // If the touch sequence is artificially cancelled by the compositor, touch motion and touch
+    // up events will be silently ignored and won't be passed down through the event filter chain.
+    // If the touch sequence is cancelled because we received a TOUCH_CANCEL event from libinput,
+    // the compositor will not receive any TOUCH_MOTION or TOUCH_UP events for that slot.
+    m_activeTouchPoints.clear();
     waylandServer()->seat()->cancelTouchSequence();
 }
 

src/touch_input.h

@@ -46,7 +46,6 @@ public:
     void processDown(qint32 id, const QPointF &pos, quint32 time, LibInput::Device *device = nullptr);
     void processUp(qint32 id, quint32 time, LibInput::Device *device = nullptr);
     void processMotion(qint32 id, const QPointF &pos, quint32 time, LibInput::Device *device = nullptr);
-    void processCancel();
     void cancel();
     void frame();
 
@@ -68,7 +67,7 @@ public:
     }
 
     int touchPointCount() const {
-        return m_touches;
+        return m_activeTouchPoints.count();
     }
 
 private:
@@ -77,14 +76,13 @@ private:
 
     void focusUpdate(Toplevel *focusOld, Toplevel *focusNow) override;
 
+    QSet<qint32> m_activeTouchPoints;
     bool m_inited = false;
     qint32 m_decorationId = -1;
     qint32 m_internalId = -1;
     QMetaObject::Connection m_focusGeometryConnection;
     bool m_windowUpdatedInCycle = false;
     QPointF m_lastPosition;
-
-    int m_touches = 0;
 };
 
 }