[Interest] [Development] Qt 5.4 multi-touchscreen problem.

[Jereme Lamothe]

I went through this process as well. The Qt libraries that ship w/ the
SDK (at least as of 5.3) are built against XInput 2.0, which is too
early for multi-touch support. In order to support touch events, I
downloaded the xinput 2.2 libraries / headers from the ubuntu
repositories and compiled Qt from source. I'm away from my linux
laptop at the moment, so am unable to say the exact package name, but
they're present in the official repos as of at least Ubuntu 12.04.

It sounds like you're doing the right thing, my only suggestions are
to double check that you have the dev headers for the xinput package,
and to run a `make confclean` before you run configure again.

I found the easiest way to test if multitouch was enabled was to
compile the fingerpaint example, and set the following environment
variable before running. It would then print out device / lib info.

QT_XCB_DEBUG_XINPUT_DEVICES=anything

I reported this issue to Digia / Qt Company through commercial
support, and was told the SDK libs were built this way intentionally
to avoid compatibility issues, which is fair enough. Hopefully they
are able to build against newer versions of xinput in future releases.

(I've cc'd the interest list rather than development, it's probably a
more appropriate place for this topic)

On Mon, Feb 23, 2015 at 5:42 PM, Celal SAVUR <c.savur at gmail.com> wrote:
> Hello Everybody,
>
> I am trying to use a multi-touch screen with my qt application. I have
> downloaded the qt 5.4 for Linux (Ubuntu 14.04). But unfortunately Gesture
> event does not deliver to the event function.
>
> My goal to catch swipe gesture then assign some task to do so.
>
> I tried to download Qt 5.4 source code then compile myself but anytime I try
> to configure the source file the flag was "mtdev no". After my research, I
> have discovered Qt required xinput 2.2 and higher but ubuntu 14.04 using
> 1.6xx.
>
> One interesting thing is that gesture (just touchbegin, touchpdate,
> touchend) is working with Qt 4.8 but not working Qt 5.4. I want to use
> Qgesture class but it does not work either 4.8 nor 5.4.
>
> I have spent too much time to fix this problem, but I could not. I need
> someone to help me to overcome this problem.
>
> Thank you in advance.
>
> celal
>
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