[Interest] Touch screen events seem opposite in Qt5.2?

Agocs Laszlo Laszlo.Agocs at digia.com
Tue Dec 31 10:17:15 CET 2013

eglfs has the evdev input handlers built-in, meaning that you will get mouse/keyboard/touch support without any additional plugins give that it is able to figure out the correct device.

In your case the touch events are coming from the evdevtouch plugin (the bits of it that are built into eglfs). With 5.1 evdevtouch failed to recognize the touchscreen on am335x, this is corrected in 5.2.

This means that you can drop -plugin tslib and set the environment variable QT_QPA_EVDEV_TOUCHSCREEN_PARAMETERS to rotate=180 in order to get the coordinates properly transformed.

If for some reason you still need to use tslib, things get a bit uglier since there is no sane way to disable the built-in input handlers in eglfs in 5.2. In 5.3 (dev branch) one can set QT_QPA_EGLFS_DISABLE_INPUT to get rid of all the built-in input stuff. Until that, you could provide a bogus device node in in QT_QPA_EVDEV_TOUCHSCREEN_PARAMETERS (e.g. set it to /dev/whatever) and launch the app with -plugin tslib. That should restore the behavior you get with 5.1.

Best regards,

From: interest-bounces+laszlo.agocs=digia.com at qt-project.org [interest-bounces+laszlo.agocs=digia.com at qt-project.org] on behalf of Rogers Nate [nate.rogers at raymondcorp.com]
Sent: Thursday, December 26, 2013 5:53 PM
To: interest at qt-project.org
Subject: [Interest] Touch screen events seem opposite in Qt5.2?

I have been using Qt5.1.1 that I cross compiled for my am335x starter kit that has the TI SDK 6.0 on it.  I am using the eglfs platform and the tslib plugin and everything works fine in Qt5.1.1.  However I when I compile Qt5.2 all of the touch screen events are coming in opposite of what was actually clicked.  For example if I click the top right of the Qt app it acts as if the bottom left was clicked.  I even receive touch events when I remove the –plugin tslib line is removed from the command arguments.  I am guessing something else is generating the touch events, but who?  I am not sure why Qt 5.1.1 worked and Qt5.2 doesn’t?  What did I break?  Any suggestions on how I can figure this out?  I am new to a lot of this stuff so any tips are appreciated, thanks in advance!


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