Installing on Rocky9 (Red Hat 9 clone)

Lana Deere

I'm running on Rocky Linux 9.0, which is a clone of Red Hat Enterprise Linux 9.0.

I built 5.15.2 and built my program using it, but I get an error running it:

qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in ""
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, webgl.

Looking at the configure output from the install, it thinks that the xcb plugin is the default, but it seems not to have been built. I tried rebuilding with an explicit -xcb on the configure command, but this time it gave me an error:

... 
Checking for default QPA platform... xcb 
...
Checking for xkbcommon >= 0.5.0... yes 
Checking for xkbcommon-x11... no
... 
Features used by QPA backends:
...
  xkbcommon .............................. yes 
  X11 specific:
    XLib ................................. yes 
    XCB Xlib ............................. yes 
    EGL on X11 ........................... no
    xkbcommon-x11 ........................ no
... 
ERROR: Feature 'xcb' was enabled, but the pre-condition 'features.thread && libs.xcb && tests.xcb_syslibs && features.xkbcommon-x11' failed.

It's hard to figure out what's going on in config.log, but I found this:

looking for library xkbcommon_x11
Trying source 0 (type pkgConfig) of library xkbcommon_x11 ... 
+ /bin/pkg-config --exists --silence-errors xkbcommon-x11
pkg-config did not find package.
  => source produced no result.
Trying source 1 (type inline) of library xkbcommon_x11 ... 
xkbcommon/xkbcommon-x11.h not found in [] and global paths.
  => source produced no result.

It looks like it thinks I should have a file xkbcommon/xkbcommon-x11.h. That file is not in the xkbcommon directory:

$ ls /usr/include/xkbcommon
     xkbcommon-compat.h   xkbcommon.h          xkbcommon-names.h
     xkbcommon-compose.h  xkbcommon-keysyms.h  xkbregistry.h

I asked the package manager about the missing xkbcommon-x11.h. It thinks that the xkbcommon.h comes from the libxkbcommon-devel package, but it also thinks there is no package which provides libxkbcommon-x11.h.

Anyone tried to install 5.15.2 on RedHat 9? Any suggestions for how to fix this?

Lana Deere

I checked on a CentOS9 machine. It also is missing xkbcommon-x11.h and the package manager thinks no pacakges provide this. So it seems to be a problem with all Red Hat 9 systems rather than something specific to Rocky9.

I also tried to Qt 5.15.6 in case that would work on RHEL9 clones, but configure fails with the same error on that system.

Lana Deere

The relevant xkbh and xcbh headers are also missing on Rocky8. Has anyone tried to build Qt 5.15.2 for X11 from source on a RHEL8 system? How did you get around this issue?