Strange touch behaviour - Qt5.3

Ferdl

Hi,

i working with Qt 5.3.2 and we have a little strange touch behaviour.
The app is running on an embedded linux 4.1
If we turn on the device the touch did not work. If we check the touch function with evtest we get some response:

Event: time 1485941574.135208, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 0
Event: time 1485941574.135208, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 494
Event: time 1485941574.135208, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 195
Event: time 1485941574.135208, ++++++++++++++ SYN_MT_REPORT ++++++++++++
Event: time 1485941574.135208, -------------- SYN_REPORT ------------

But the qt app did not recognize the input.

At first I have to touch with two fingers once. After that the touch is working as expected with single touch.

Event: time 1485941835.927475, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 0
Event: time 1485941835.927475, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 309
Event: time 1485941835.927475, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 110
Event: time 1485941835.927475, ++++++++++++++ SYN_MT_REPORT ++++++++++++
Event: time 1485941835.927475, -------------- SYN_REPORT ------------
Event: time 1485941835.939073, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 240
Event: time 1485941835.939073, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 309
Event: time 1485941835.939073, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 110
Event: time 1485941835.939073, ++++++++++++++ SYN_MT_REPORT ++++++++++++
Event: time 1485941835.939073, -------------- SYN_REPORT ------------
Event: time 1485941835.950430, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 240
Event: time 1485941835.950430, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 309
Event: time 1485941835.950430, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 109
Event: time 1485941835.950430, ++++++++++++++ SYN_MT_REPORT ++++++++++++
Event: time 1485941835.950430, -------------- SYN_REPORT ------------

Did anyone have a idea what kind of reason this has?

The app will be started with this:

export QT_QPA_EVDEV_TOUCHSCREEN_PARAMETERS=/dev/input/event0

The touch driver and the touch is a Multitouch (two fingers).

Thanks