Pinch Gesture are not recognized in PinchArea on Wayland with a Wacom Pro tablet

Note: I can try to debug this issue if I get some hints...

Context:

I am trying to mock up a pinch gesture on desktop to do coarse debugging of an Android application. But it can also improve the support of Wacom pro tablet in Qt.

Solutions could be

• use the Android emulator : this is slower than native
• use a computer with a touchscreen : expensive
• inject touch events in Qt : aka Qt Test
• use a tablet with a touchpad (on Wayland) : cost ~ 200€
• forward and inject touch events from a smartphone to the desktop : cheaper, but must implement it... QML Android toy app -> send events over IP -> Application on desktop -> inject events in Qt event loop

Test environment:

• OS is Fedora 36 on Wayland
• Tablet is a Wacom Intuos Pro with a touchpad
• Test application is a custom QML demo with MouseArea, MultiPointTouchArea, PinchArea, PinchHandler, PointHandler, TapHandler
• source https://github.com/FabriceSalvaire/qt-examples/blob/main/python-examples/input-device/view.qml

Results:

• [OK] mouse with one finger: move, click, double click
• [OK]  (X, Y) wheel with one static finger and a second one moving, or double moving fingers. Horizontal wheel is more erratic and increase to the left !!
• [OK] PinchHandler: target scale and rotate
• [NOK] PinchArea: no signals, no action on target
• PointHandler requires a double tap and move to act as the mouse to drag an item???
• for MultiPointTouchArea, Wayland doesn't send any events...

Wayland trace:

Pinch gesture event are sent to the application

[ 624509.430] zwp_pointer_gesture_pinch_v1@21.begin(23109, 16609422, wl_surface@27, 2)

[ 624509.589] zwp_pointer_gesture_pinch_v1@21.update(16609422, 1.16796875, -1.65625000, 0.98046875, 0.14453125)
...

[ 626129.266] zwp_pointer_gesture_pinch_v1@21.end(23110, 16611041, 0)

See https://wayland.app/protocols/pointer-gestures-unstable-v1

Notice Wayland only send gesture event. Raw touch events are available from libinput (tested with evtest).

I don't found any swipe events in the log.

zwp_pointer_gesture_pinch_v1 occurrences in Qt Wayland source are found in these files

• src/3rdparty/protocol/pointer-gestures-unstable-v1.xml
• src/client/qwaylandpointergestures_p.h
• src/client/qwaylandpointergestures.cpp