Clarification on the usage of XDG_DATA_DIRS

[xEnVrE]

Recently I have tried to setup a robotology-superbuild install on my system (Arch Linux with 5.18.7-arch1-1 kernel).

After sourcing the build/install/share/robotology-superbuild/setup.sh file, as per https://github.com/robotology/robotology-superbuild#configure-your-environment, I found out that my system could not run any UI dialog reliably anymore as many of the png files associated to icons could not be found. This was causing erratic crashes or strange behaviors.

After investigating a bit I found that the setup.sh file sets the XDG_DATA_DIRS as follows:

robotology-superbuild/cmake/template/setup.sh.in

Line 17 in bab995b

export XDG_DATA_DIRS=${XDG_DATA_DIRS:+${XDG_DATA_DIRS}:}$ROBOTOLOGY_SUPERBUILD_INSTALL_PREFIX/share

Unfortunately, in some systems, as the one I am using apparently, if the XDG_DATA_DIRS is not set or empty, a default value of /usr/local/share/:/usr/share/ is assumed. However, when the XDG_DATA_DIRS is populated by the setup.sh, given that it is empty, the new value will just contain <path_to_ROBOTOLOGY_SUPERBUILD_INSTALL_PREFIX>/share, i.e. the reference to /usr/local/share and /usr/share is missing.

Of course, this seems to be very system-dependent and might be easily solved if the user exports XDG_DATA_DIRS correctly. However, on some systems this might create strange behaviors and it is difficult to track them down and associate them with the robotology-superbuild installation.

Wondering if you could suggest anything to mitigate the problem, e.g. adding even a simple disclaimer in the README.

Thanks

cc @traversaro

[traversaro]

Thanks for reporting the issue so clearly. This is a indeed a pain point, in the setup.sh we should just append to XDG_DATA_DIRS if it is not defined, otherwise we should first define it as /usr/local/share/:/usr/share/ and only later append, I will try to fix this issue.

For reference, this is the reason why this was added in the first place:

• Investigate automatic support for autocomplete integration #622
• Add <superbuild_install_prefix>/share to XDG_DATA_DIRS environment variable to support yarp bash autocompletion out of the box #759

@HosameldinMohamed just a curiosity, did you ever experienced something like that?

[xEnVrE]

Thanks for the explanation @traversaro

[HosameldinMohamed]

@HosameldinMohamed just a curiosity, did you ever experienced something like that?

No, for me it seems fine, here's my XDG_DATA_DIRS value:

/home/hosameldin/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share:/usr/share:/var/lib/snapd/desktop:/home/hosameldin/code/robotology-superbuild/build/install/share

However I am using Manjaro, and it comes with a lot of packages pre-installed and many values pre-configured. So I am not sure this is comparable to this case.

Interestingly, I have an Archlinux system at home and I didn't encounter this issue there as well, but probably I have installed something that set XDG_DATA_DIRS before configuring the superbuild, such as Snap or Flatpak.

[xEnVrE]

Interestingly, I have an Archlinux system at home and I didn't encounter this issue there as well, but probably I have installed something that set XDG_DATA_DIRS before configuring the superbuild, such as Snap or Flatpak.

I can confirm I did not install any of those and by default my system does not have the XDG_DATA_DIRS exported.

[traversaro]

Interesting, I wonder that if this packages set the XDG_DATA_DIRS, they make sure to set it to /usr/local/share:/usr/share before appending more values.

[HosameldinMohamed]

Interesting, I wonder that if this packages set the XDG_DATA_DIRS, they make sure to set it to /usr/local/share:/usr/share before appending more values.

Probably that's what you are looking for https://github.com/flatpak/flatpak/blob/main/profile/flatpak.sh

[traversaro]

Interesting, I wonder that if this packages set the XDG_DATA_DIRS, they make sure to set it to /usr/local/share:/usr/share before appending more values.

Probably that's what you are looking for https://github.com/flatpak/flatpak/blob/main/profile/flatpak.sh

Indeed, the line https://github.com/flatpak/flatpak/blob/3a93ef4842f7dac3eed02e2a45091cd358162b6a/profile/flatpak.sh#L25 seems to do almost exactly that.

[traversaro]

With @RiccardoZuppetti we experienced another nasty bug relatedo to this, in a Docker image in which snapd was not installed and so where XDG_DATA_DIRS was not defined. In particular, there matplotlib was not working with error:

 File "/home/riccardozuppetti/git/adherent/src/adherent/trajectory_control/trajectory_controller.py", line 671, in retrieve_contacts
    plt.figure()
  File "/home/riccardozuppetti/.local/lib/python3.8/site-packages/matplotlib/pyplot.py", line 787, in figure
    manager = new_figure_manager(
  File "/home/riccardozuppetti/.local/lib/python3.8/site-packages/matplotlib/pyplot.py", line 306, in new_figure_manager
    return _backend_mod.new_figure_manager(*args, **kwargs)
  File "/home/riccardozuppetti/.local/lib/python3.8/site-packages/matplotlib/backend_bases.py", line 3494, in new_figure_manager
    return cls.new_figure_manager_given_figure(num, fig)
  File "/home/riccardozuppetti/.local/lib/python3.8/site-packages/matplotlib/backend_bases.py", line 3500, in new_figure_manager_given_figure
    manager = cls.FigureManager(canvas, num)
  File "/home/riccardozuppetti/.local/lib/python3.8/site-packages/matplotlib/backends/backend_gtk3.py", line 324, in __init__
    self.window.set_icon_from_file(window_icon)
gi.repository.GLib.Error: gdk-pixbuf-error-quark: Couldn’t recognize the image file format for file “/home/riccardozuppetti/.local/lib/python3.8/site-packages/matplotlib/mpl-data/images/matplotlib.svg” (3)

Better to finally fix this before we waste more time on it.