View Full Version : qvfb problem

29th March 2007, 18:00
Hello all,

I performed the following steps to get ready to use the virtual framebuffer:

1. Built and installed Qt 4.2.1 using the -qvfb flag in the configure step
2. cd'd to <Qt install dir>/tools/qvfb
3. Ran make
4. Ran make install

Then to use the virtual framebuffer I ran:

<qt bin dir>/qvfb -width 640 -height 480 -qwsdisplay QVFb:0 &

At this point I see the virtual framebuffer application on my screen.

Then I run

./mygui -qws -display "QVFb:0"

I get the following error:

_X11TransSocketINETConnect() can't get address for QVFb:6000: Name or service not known
gui: cannot connect to X server QVFb:0

Any ideas about how to fix this would be greatly appreciated.


8th April 2007, 03:32
Looks like you may of compiled your application against Qtx11.

22nd January 2008, 16:33
I know this thread is quite old, but I am facing the same problem. If lpotter is right, how can I compile my application against qvfb in order to use it and not x11? How can I use qmake in order to link it against qvfb? Do I have to modify the .pro files to add there a linker options? I configured qtopia-core with the qvfb support, so it should be enough, shouldn't it?

23rd January 2008, 10:33
"QVFb is an X11 application supplied with Qt/X11 that provides a virtual framebuffer for Qtopia Core to use"

Then: your executable shall be built with Qtopia Core and not with QT. :)

24th January 2008, 08:23
Then: your executable shall be built with Qtopia Core and not with QT.

And that's exactly what I am doing: I have compiled Qt/X11 with qvfb support, then I compiled the Qt/X11 tool qvfb, and finally qtopia core. When I compile my application I do it under qtopia core and not under Qt/X11, like it seems that you have understood. I open the qvfb built in Qt/X11 and the application buildt with qtopia-core, but it doesn't work. Any other idea?

24th January 2008, 13:39
Once the virtual framebuffer (the qvfb application) is running, it is ready for use: Start a server application (i.e. construct a QApplication object with the QApplication::GuiServer flag or use the -qws command line parameter. See the running applications documentation for details). For example:
cd path/to/Qtopia/Core/examples/widgets/analogclock
./analogclock -qws
Note that as long as the virtual framebuffer is running and the current Qtopia Core configuration supports qvfb, Qtopia Core will automatically detect it and use it by default. Alternatively, the -display option can be used to specify the virtual framebuffer driver. For example:
cd path/to/Qtopia/Core/examples/widgets/analogclock
./analogclock -qws -display QVFb:0
Warning: If qvfb is not running (or the current Qtopia Core configuration doesn't support it) and the driver is not explicitly specified, Qtopia Core will write to the real framebuffer and the X11 display will be corrupted.

Thành Viên Mới
9th November 2010, 04:42
i known this thread is quite old,but i am facing the same problem, when i run my program : ./books -qws -display "QVFb:0"

then it message error: cannot connect to X server QVFb:0
can you help me

9th February 2011, 05:58
If you're still having problems, check out my post on this thread: http://www.qtcentre.org/threads/37822-Problems-using-QVFB-on-Ubuntu

Let me know if this works for you!