[Development] X11/XCB QPA: QPlatformIntegration::ThreadedOpenGL returning false

James Turner james.turner at kdab.com
Mon Aug 12 11:44:07 CEST 2013

On 12 Aug 2013, at 10:36, Robin Burchell <robin+qt at viroteck.net> wrote:

> The reader will be running or not, set here in QXcbConnection::QXcbConnection:
>    m_reader = new QXcbEventReader(this);
>    connect(m_reader, SIGNAL(eventPending()), this,
> SLOT(processXcbEvents()), Qt::QueuedConnection);
>    connect(m_reader, SIGNAL(finished()), this, SLOT(processXcbEvents()));
>    if (!m_reader->startThread()) {
> ...
> And startThread checks for the existence of
> m_xcb_poll_for_queued_event, which is searched for in
> QXcbEventReader::QXcbEventReader:
>    m_xcb_poll_for_queued_event =
> (XcbPollForQueuedEventFunctionPointer)dlsym(RTLD_DEFAULT,
> "xcb_poll_for_queued_event");
> #endif
> So I'd guess either you have RTLD_DEFAULT not defined (probably not
> the case, if this is a fairly stock linux system) or your xcb install
> is out of date, as AFAIK this was only released fairly recently.

Thanks for the info.

That's quite plausible - I did look at the code above, but I was unaware of how likely (or unlikely) it would be for the various #defines and run-time checks to be satisfied.

This raises the question of what the interaction is between this entry point ('xcb_poll_for_queued_event') and support for threaded OpenGL however. 

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