@davidsu3344 said in [Solved] How to use Qt5 with X11?:

but the connection speed is extremly slow

What connection do you mean?

Compiled and rebuilt with Qt5.5.0 (beta).

Interestingly, the warnings I received when running over VNC or when in high-dpi mode (QT_DEVICE_PIXEL_RATIO=2) no longer appear with Qt5.5.0. So, this is a definite improvement.

However, I still receive the 147 (Unknown) error on launch when running over X11 forwarding.

I have similar problem with running Wireshark GUI on Centos7 using XMing on Windows 10.

I was trying to debug this issue, but it seems to be inside Qt libraries. The QtApplication constructor print "failed to get the current screen resources", and after quite a lot of code application finished at this line:

main_window->show()

with message:
The X11 connection broke: I/O error (code 1)
XIO: fatal IO error 2 (No such file or directory) on X server "localhost:14.0"
after 363 requests (363 known processed) with 0 events remaining.

Just to be clear, it's not app crash, I did not describe it good.
Sometimes fullscreen mode look messy(look at image), let say it's happening every 10th time.
But, I can exit from that messy fullscreen and video plays in normal mode.

I tried:

resize(QApplication::desktop()->width(), QApplication::desktop()->height());

But no effect.

@SGaist
I have Gamma Ray, I guess it can help.
Which informations are relevant?