Is a TOUCH_DOWN directly followed by TOUCH_MOTION with the same position okay?
Summary
A classical Qt application (no QML) running on the custom embedded system described below showed no response to touch events. The problem has been tracked down, reported as a Qt bug (see https://bugreports.qt.io/browse/QTBUG-79212) and a patch for Qt solving the problem has been proposed (see https://codereview.qt-project.org/c/qt/qtbase/+/277476).
Now my question is: is it defined and expected behaviour to get a LIBINPUT_EVENT_TOUCH_DOWN directly followed by a LIBINPUT_EVENT_TOUCH_MOTION both having the same touch position as a start of the response to a single one finger tap? I ask as I would like to know if I actually fixed the problem or only worked around it? (As it probably has to be fixed in libinput or in the touch controller's linux driver). So your expert knowledge is really appreciated.
Steps to reproduce
Start an arbitrary QWidget based Qt application and tap with one finger on the resistive touch screen - no QEvents are ever reaching the QApplication.
libinput version you encountered the bug on
libinput-1.12.6
Hardware information:
Platform with Texas Instruments's ADS7846 touch screen controller (NXP i.MX6 DualLite SoC) and a LOGIC Technologies Inc. LTTD800x480 L2RT 7" (800x480 pixels) TFT LCD panel attached to it (resistive touch) using Linux v5.2.17, Qt 5.12.3 (QT_QPA_PLATFORM=eglfs which utilizes libinput by default). The image being run is built using Yocto 2.7.1.
Other log output:
-
libinput record
output: recording.yml -
libinput debug-events --verbose
output: events.log