xcb: Properly calculate the size of the touch rect

ABS_MT_TOUCH_MAJOR is given in surface units rather than in finger units.
Also it's not the width of the touch rect but the length of the major axis
of the contact. Currently we don't support the orientation of touch rects,
so report square rects with side length of ABS_MT_TOUCH_MAJOR.

Change-Id: I16c861f30128438ec4a1cae983700f8da4b7b4b7
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>

1 files changed, 5 insertions, 14 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp b/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
index c43816fa05..1848fc14f0 100644
--- a/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
@@ -43,7 +43,6 @@
 
 #include <X11/extensions/XInput2.h>
 #include <X11/extensions/XI2proto.h>
-#define FINGER_MAX_WIDTH_MM 10
 
 struct XInput2TouchDeviceData {
     XInput2TouchDeviceData()
@@ -517,7 +516,7 @@ void QXcbConnection::xi2HandleEvent(xcb_ge_event_t *event)
                 QWindowSystemInterface::TouchPoint &touchPoint = m_touchPoints[xiDeviceEvent->detail];
                 qreal x = fixed1616ToReal(xiDeviceEvent->root_x);
                 qreal y = fixed1616ToReal(xiDeviceEvent->root_y);
-                qreal nx = -1.0, ny = -1.0, w = 0.0, h = 0.0;
+                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];
@@ -543,13 +542,7 @@ void QXcbConnection::xi2HandleEvent(xcb_ge_event_t *event)
                         } else if (vci->label == atom(QXcbAtom::AbsMTPositionY)) {
                             ny = valuatorNormalized(value, vci);
                         } else if (vci->label == atom(QXcbAtom::AbsMTTouchMajor)) {
-                            // Convert the value within its range as a fraction of a finger's max (contact patch)
-                            //  width in mm, and from there to pixels depending on screen resolution
-                            w = valuatorNormalized(value, vci) * FINGER_MAX_WIDTH_MM *
-                                screen->geometry().width() / screen->physicalSize().width();
-                        } else if (vci->label == atom(QXcbAtom::AbsMTTouchMinor)) {
-                            h = valuatorNormalized(value, vci) * FINGER_MAX_WIDTH_MM *
-                                screen->geometry().height() / screen->physicalSize().height();
+                            d = valuatorNormalized(value, vci) * screen->geometry().width();
                         } else if (vci->label == atom(QXcbAtom::AbsMTPressure) ||
                                    vci->label == atom(QXcbAtom::AbsPressure)) {
                             touchPoint.pressure = valuatorNormalized(value, vci);
@@ -566,10 +559,8 @@ void QXcbConnection::xi2HandleEvent(xcb_ge_event_t *event)
                     ny = y / screen->geometry().height();
                 }
                 if (xiEvent->evtype != XI_TouchEnd) {
-                    if (w == 0.0)
-                        w = touchPoint.area.width();
-                    if (h == 0.0)
-                        h = touchPoint.area.height();
+                    if (d == 0.0)
+                        d = touchPoint.area.width();
                 }
 
                 switch (xiEvent->evtype) {
@@ -606,7 +597,7 @@ void QXcbConnection::xi2HandleEvent(xcb_ge_event_t *event)
                     }
                     dev->pointPressedPosition.remove(touchPoint.id);
                 }
-                touchPoint.area = QRectF(x - w/2, y - h/2, w, h);
+                touchPoint.area = QRectF(x - d/2, y - d/2, d, d);
                 touchPoint.normalPosition = QPointF(nx, ny);
 
                 if (Q_UNLIKELY(lcQpaXInput().isDebugEnabled()))