QT5.4.1 application doesn't respond to touch while evtest reports correct x,y

ankurtyagi

Hi,

I am using Qt5.4.1 on Arm cortex A8 Linux based platform. I have connected a 800x480 capacitive touch screen.
evtest reports correct x,y co-ordinates if I touch on all four corners but Qt app doesn't detect touch.

I have tested my Qt app on a different touch device and it works.

What else could be the reason for it not to work ?

thanks
Ankur

SGaist

Hi,

What plugin are you using for input ?

Leonardo

You should try using tslib.

http://doc.qt.io/qt-5/embedded-linux.html#touch

ankurtyagi

Hi,

@Qt-Champions-2015
I have built Qt to use eglfs and eglfs has all the evdev input handling code built-in.

@Leonardo
I am using a capacitive touch screen based on FT5x06. As per documentation, I don't need tslib.
Do you have any other rationale for using tslib ?

regards
Ankur

Leonardo

You shouldn't need it, but the truth is that sometimes tslib is the only one to work. In addition, I have already had the same problem with the same capacitive touch and Qt version.

ankurtyagi

So in order to override inbuilt evdev support for eglfs platform, I should build Qt with tslib support and set QT_QPA_EGLFS_TSLIB and TSLIB_DEVICE in environment ?

Leonardo

Yes. It's also possible to use a command line argument. Here's the shell script I use to launch my application:

#!/bin/sh
dirname=`dirname $0`
tmp="${dirname#?}"
if [ "${dirname%$tmp}" != "/" ]; then
dirname=$PWD/$dirname
fi
LD_LIBRARY_PATH="$dirname:/lib:/usr/lib:/usr/local/lib"
QT_QPA_PLATFORM="eglfs"
QT_QPA_EGLFS_DISABLE_INPUT=1
TSLIB_TSDEVICE=/dev/input/event1
QT_QPA_EGLFS_HIDECURSOR=1
export LD_LIBRARY_PATH
export QT_QPA_PLATFORM
export QT_QPA_EGLFS_DISABLE_INPUT
export TSLIB_TSDEVICE
export QT_QPA_EGLFS_HIDECURSOR
$dirname/application -plugin tslib

ankurtyagi

Thanks Leonardo, using Qt with Tslib fixed the problem.