Widgets stop responding when enabling gestures on (evdev) multitouch device

[Cédric Dufour]

Hello,

Using Qt 4.8.2 on Ubuntu/Quantal (amd64) on a touchscreen device (Samsung XE700, Atmel MaxTouch, stock hid-multitouch+evdev driver), I found out that all widgets stop to work - iow. react to single-finger touch ("mouse press") - as soon as one enables a gesture - e.g. grabGesture( Qt::PinchGesture ) - on a widget.

What is weird is that enabling the Tap gesture on a non-responding widget makes it reponsive again. But one can not go into enabling the Tap gesture on all widgets in an application (I have an application with hundreds of them, some I can't even access; e.g. the "close" button on QStackWidget tabs)

I attach a simple test case that allows to reproduce the problem systematically (see README for further details).

Let me know if I can help.

Best regards,

Cédric Dufour

libqt4-core: 4.8.2+dfsg-2ubuntu1
xserver-xorg-input-evdev: 2.7.3-0ubuntu1
linux-image-3.5.0-14-generic (hid-multitouch): 3.5.0-14.19
lsusb (Atmel MaxTouch): Bus 002 Device 005: ID 03eb:211c Atmel Corp.