How to disable Gtk-Message warnings in your app

So every elementary OS app at the moment, if you start it from Terminal, welcomes you with a variation of the following salutation:

Gtk-Message: … : Failed to load module "canberra-gtk-module"
Gtk-Message: … : Failed to load module "canberra-gtk-module"

Isn’t that friendly?

The journey begins…

I initially thought this was a long-standing issue with Flatpak (and I was a shady bitch about it too) but, thanks to a detailed write-up by Simon McVittie, we now know that it is more likely due to a configuration mismatch between the host OS (in this case elementary OS 6) and the runtime in your Flatpak.¹

So just turn off those warnings in your app if they bother you so much, I hear you say.

Well, reader, it’s not that simple.

After hitting my head on a brick wall (also known as GNOME/GTK documentation) for a few hours to no avail, I opened an issue on the GTK tracker, using it like Discourse as if I’d been raised in a barn like some sort of animal.

Thanks to Emmanuele Bassi’s hints in his response, I was able to finally find a way to disable the Gtk-Message warnings.

A happy ending

All you have to do², see, is create a custom log writer function.

Here’s an excerpt of the relevant bits from the app I’m building in case they help you too:

public class Application : Gtk.Application {
    public static string flatpak_id;
    public static bool is_running_as_flatpak;

    public Application () {

    public static int main (string[] commandline_arguments) {
        flatpak_id = Environment.get_variable ("FLATPAK_ID");
        is_running_as_flatpak = flatpak_id != null;

        if (is_running_as_flatpak) {
            Log.set_writer_func (log_writer);
        }

        return new Application ().run (commandline_arguments);
    }

    private static LogWriterOutput log_writer (LogLevelFlags log_level, [CCode (array_length_type = "gsize")] LogField[] fields) {
        return log_level == LogLevelFlags.LEVEL_MESSAGE ? LogWriterOutput.HANDLED : LogWriterOutput.UNHANDLED;
    }
}

Epilogue

Hopefully, knowing the folks at elementary OS, they’ll get to the bottom of the issue so we won’t need this workaround in the near future.

In the meanwhile, I plan on adding this to Watson – the best-practices application template for elementary OS 6 (Odin) that I’m working on, so that any apps created based on it will silence these warnings by default.

There is a lot to admire about Gtk+, really there is³, but sometimes it does feel like you have to construct a Rube Goldberg machine just to do the simplest things.