QWindowSystemInterface: Fix wrong mapping of coordinates.

QTouchEvent::TouchPoint assumes the rect() is in local coordinates,
whereas QWindowSystemInterface::TouchPoint uses screen coordinates.
We must therefore use QWindowSystemInterface::TouchPoint::area as the
screenRect() rather that the rect() and then use the screen coordinate
to calculate the local coordinate by using mapFromGlobal.

Change-Id: If7a52f5668c3938f46bdd38a5ea82b5313d6b626
Reviewed-on: http://codereview.qt-project.org/5253
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Bjørn Erik Nilsen <bjorn.nilsen@nokia.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/src/gui/kernel/qwindowsysteminterface_qpa.cpp b/src/gui/kernel/qwindowsysteminterface_qpa.cpp
index d862d05baa..898de3a425 100644
--- a/src/gui/kernel/qwindowsysteminterface_qpa.cpp
+++ b/src/gui/kernel/qwindowsysteminterface_qpa.cpp
@@ -230,8 +230,20 @@ void QWindowSystemInterface::handleTouchEvent(QWindow *tlw, ulong timestamp, QEv
             state |= Qt::TouchPointPrimary;
         }
         p.setState(state);
-        p.setRect(point->area);
-        p.setScreenPos(point->area.center());
+
+        const QPointF screenPos = point->area.center();
+        p.setScreenPos(screenPos);
+        p.setScreenRect(point->area);
+
+        // Map screen pos to local (QWindow) coordinates and preserve sub-pixel resolution.
+        const QPointF delta = screenPos - screenPos.toPoint();
+        const QPointF localPos = tlw->mapFromGlobal(screenPos.toPoint()) + delta;
+        p.setPos(localPos);
+
+        QRectF rect(0, 0, point->area.width(), point->area.height());
+        rect.moveCenter(localPos);
+        p.setRect(rect);
+
         p.setNormalizedPos(point->normalPosition);
 
         touchPoints.append(p);