xcb: Map touch points to screen coordinates

Add QPointF overloads for QXcbScreen::mapToNative() and
QXcbScreen::mapFromNative(). Use mapFromNative() to map
the coordinates of a touch point to screen coordinates
as we do it for mouse events. It fixes touch events when
QT_DEVICE_PIXEL_RATIO is set.

Change-Id: Id8362cda526e0f837b76899eba21d9bfc895988c
Task-number: QTBUG-44840
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp b/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
index b862bab417..2f46436ce2 100644
--- a/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
@@ -562,10 +562,12 @@ void QXcbConnection::xi2ProcessTouch(void *xiDevEvent, QXcbWindow *platformWindo
         dev->touchPoints[tp.id] = tp;
     }
     QWindowSystemInterface::TouchPoint &touchPoint = dev->touchPoints[xiDeviceEvent->detail];
-    qreal x = fixed1616ToReal(xiDeviceEvent->root_x);
-    qreal y = fixed1616ToReal(xiDeviceEvent->root_y);
+    QXcbScreen* screen = platformWindow->xcbScreen();
+    QPointF pos = screen->mapFromNative(QPointF(fixed1616ToReal(xiDeviceEvent->root_x),
+                                                fixed1616ToReal(xiDeviceEvent->root_y)));
+    qreal x = pos.x();
+    qreal y = pos.y();
     qreal nx = -1.0, ny = -1.0, d = 0.0;
-    QXcbScreen* screen = m_screens.at(0);
     for (int i = 0; i < dev->xiDeviceInfo->num_classes; ++i) {
         XIAnyClassInfo *classinfo = dev->xiDeviceInfo->classes[i];
         if (classinfo->type == XIValuatorClass) {