[Interest] Qt5/eglfs coredump in QGL2PaintEngineEx::begin due to null QGLContext.

[Samuel Rødal]

On 02/13/2012 01:50 AM, ext Jon Trulson wrote:
> Hi, I'm building Qt5 (latest from git) on an arm board (imx53 QSB).  I
> am not using X11.  I am using the eglfs plugin.
>
> I have attempted to run several of the qtbase demos (like
> animatedtiles).  In all cases, I get a SEGV in
> qpaintengineex_opengl2.cpp:1960 (QGL2PaintEngineEx::begin()).
>
> This code looks like:
>     1959:    d->ctx = d->device->context();
>     1960:    d->ctx->d_ptr->active_engine = this;
>
> d->device->context() is returning NULL, and of course it then cores
> when it tries to deref it on line 1960.
>
> I have gone through the eglfs plugin code in as much detail as I can -
> The egl display and window surfaces are being created and initialized
> properly, and seem to return sane values.  The eglCreateContext()
> calls in qeglplatformcontext.cpp are working and returning sane
> results.
>
> So - where/when is this QGLContext supposed to be created?  And why is
> it not being created :)
>
> I am very new to the guts of Qt, so please forgive me if I'm missing
> something stupid.  Any ideas or suggestions are definitely welcome.
>
> Thanks.
>
>
> PS:  I case it's useful, here are a few lines from the backtrace in
> gdb (frame #1 is where the trouble is):
>
> #0  0x2c4eb7f4 in QScopedPointer<QGLContextPrivate, QScopedPointerDeleter<QGLContextPrivate>  >::operator->  (this=0x4)
>       at ../../include/QtCore/../../src/corelib/tools/qscopedpointer.h:109
> #1  0x2c520cd8 in QGL2PaintEngineEx::begin (this=0x358d8, pdev=0x355a8)
>       at gl2paintengineex/qpaintengineex_opengl2.cpp:1960
> #2  0x2b68c558 in QPainter::begin (this=0x7eedf430, pd=0x355a8)
>       at painting/qpainter.cpp:1826
> #3  0x2b68ab28 in QPainter (this=0x7eedf430, pd=0x2f868)
>       at painting/qpainter.cpp:1470
> #4  0x2ac371b0 in QWidgetPrivate::drawWidget (this=0x2f878, pdev=0x355a8,
>       rgn=@0x7eedf550, offset=@0x7eedf59c, flags=4, sharedPainter=0x0,
>       backingStore=0x35350) at kernel/qwidget.cpp:5091
>
> I have more if you like :)

I'd recommend trying qmlscene or examples/opengl/hellowindow --single 
here as well, as I'm not sure eglfs supports multiple top-levels. A 
QGLWidget embedded in a widget hierarchy will always force a top-level 
platform window to be created, since it needs its own EGLSurface (or 
similar on other platforms).

--
Samuel