implement event propagation for touch events

behavior is similar to that of QGraphicsScene mouse events: the first
touch event (the TouchBegin) is propagated to all parents. if a widget
accepts the event, it will receive all other touch events (the
TouchUpdate and TouchEnd events). If no widget accepts the TouchBegin,
then we will fallback to normal mouse events (TBD).

3 files changed, 53 insertions, 0 deletions

diff --git a/src/gui/kernel/qapplication.cpp b/src/gui/kernel/qapplication.cpp
index 34c2d74ddf..9c70208441 100644
--- a/src/gui/kernel/qapplication.cpp
+++ b/src/gui/kernel/qapplication.cpp
@@ -85,6 +85,7 @@
 #include <stdlib.h>
 
 #include "qapplication_p.h"
+#include "qevent_p.h"
 #include "qwidget_p.h"
 
 #include "qapplication.h"
@@ -4027,7 +4028,41 @@ bool QApplication::notify(QObject *receiver, QEvent *e)
         }
         break;
 #endif
+    case QEvent::TouchBegin:
+    // Note: TouchUpdate and TouchEnd events are sent to d->currentMultitouchWidget and never propagated
+    {
+        QWidget *widget = static_cast<QWidget *>(receiver);
+        QTouchEvent *touchEvent = static_cast<QTouchEvent *>(e);
+        bool eventAccepted = touchEvent->isAccepted();
+
+        if (widget->testAttribute(Qt::WA_AcceptTouchEvents) && e->spontaneous()) {
+            // give the widget focus if the focus policy allows it
+            QApplicationPrivate::giveFocusAccordingToFocusPolicy(widget,
+                                                                 Qt::ClickFocus,
+                                                                 Qt::MouseFocusReason);
+        }
+
+        while (widget) {
+            // first, try to deliver the touch event
+            touchEvent->ignore();
+            res = widget->testAttribute(Qt::WA_AcceptTouchEvents)
+                  && d->notify_helper(widget, touchEvent);
+            eventAccepted = touchEvent->isAccepted();
+            touchEvent->spont = false;
+            if (res && eventAccepted) {
+                // the first widget to accept the TouchBegin gets an implicit grab.
+                d->currentMultitouchWidget = widget;
+                break;
+            } else if (widget->isWindow() || widget->testAttribute(Qt::WA_NoMousePropagation)) {
+                break;
+            }
+            widget = widget->parentWidget();
+            d->updateTouchPointsForWidget(widget, touchEvent);
+        }
 
+        touchEvent->setAccepted(eventAccepted);
+        break;
+    }
     default:
         res = d->notify_helper(receiver, e);
         break;
@@ -5046,6 +5081,19 @@ bool QApplicationPrivate::shouldSetFocus(QWidget *w, Qt::FocusPolicy policy)
     return true;
 }
 
+void QApplicationPrivate::updateTouchPointsForWidget(QWidget *widget, QTouchEvent *touchEvent)
+{
+    for (int i = 0; i < touchEvent->_touchPoints.count(); ++i) {
+        QTouchEvent::TouchPoint *touchPoint = touchEvent->_touchPoints.at(i);
+
+        // preserve the sub-pixel resolution
+        const QPointF delta = touchPoint->d->globalPos - touchPoint->d->globalPos.toPoint();
+        touchPoint->d->pos = widget->mapFromGlobal(touchPoint->d->globalPos.toPoint()) + delta;
+        touchPoint->d->startPos = widget->mapFromGlobal(touchPoint->d->startGlobalPos.toPoint()) + delta;
+        touchPoint->d->lastPos = widget->mapFromGlobal(touchPoint->d->lastGlobalPos.toPoint()) + delta;
+    }
+}
+
 QT_END_NAMESPACE
 
 #include "moc_qapplication.cpp"
diff --git a/src/gui/kernel/qapplication_p.h b/src/gui/kernel/qapplication_p.h
index 6d75f373db..252d0cb36d 100644
--- a/src/gui/kernel/qapplication_p.h
+++ b/src/gui/kernel/qapplication_p.h
@@ -424,6 +424,9 @@ public:
     void sendSyntheticEnterLeave(QWidget *widget);
 #endif
 
+    QPointer<QWidget> currentMultitouchWidget;
+    static void updateTouchPointsForWidget(QWidget *widget, QTouchEvent *touchEvent);
+
 private:
 #ifdef Q_WS_QWS
     QMap<const QScreen*, QRect> maxWindowRects;
diff --git a/src/gui/kernel/qevent.h b/src/gui/kernel/qevent.h
index 3cb712d37d..506e0c14d3 100644
--- a/src/gui/kernel/qevent.h
+++ b/src/gui/kernel/qevent.h
@@ -758,6 +758,8 @@ public:
 
 protected:
     QList<TouchPoint *> _touchPoints;
+
+    friend class QApplicationPrivate;
 };
 
 QT_END_NAMESPACE