Daniel Lange's blog

Installing a laptop with the shiny new Debian Bookworm release finds a few interesting things broken that I probably had fixed in the past already on the old laptop.

One, that was increadibly unintuitive to fix, was lots of applications (like xfce4-terminal or Telegram) opening links in Chromium despite Firefox being set as the preferred webbrowser everywhere.

update-alternatives --config x-www-browser was pointing at Firefox already, of course.
The Xfce4 preferred application from settings was Firefox, of course.
xdg-mime query default text/html delivered firefox-esr.desktop, of course.

Still nearly every link opens in ███████ Chromium...

As usually the answer is out there. In this case in a xfce4-terminal bug report from 2015.

The friendly "runkharr" has debugged the issue and provides the fix as well. As usually, all very easy once you know where to look. And why to hate GTK again a bit more:

The GTK function gtk_show_uri() uses glib's g_app_info_launch_default_for_uri() and that - of course - cannot respect the usual mimetype setting.

So quoting "runkharr" verbatim:

1. Create a file `exo-launch.desktop´ in your `~/.local/share/applications´ directory with something like the following content:

    [Desktop Entry]
    Name=Exo Launcher
    Type=Application
    Icon=gtk-open
    Categories=Desktop;
    Comment=A try to force 'xfce4-terminal' to use the preferred application(s)
    GenericName=Exo Launcher
    Exec=exo-open %u
    MimeType=text/html;application/xhtml+xml;x-scheme-handler/http;x-scheme-handler/https;x-scheme-handler/ftp;application/x-mimearchive;
    Terminal=false
    OnlyShowIn=XFCE;

2. Create (if not already existing) a local `defaults.list´ file, again in your `~/.local/share/applications´ directory. This file must start with a "group header" of

    [Default Applications]

3. Insert the following three lines somewhere below this `[Default Applications]´ group header [..]:

    x-scheme-handler/http=exo-launch.desktop;
    x-scheme-handler/https=exo-launch.desktop;
    x-scheme-handler/ftp=exo-launch.desktop;

And ... links open in Firefox again. Thank you "runkharr"!

The font size Mozilla chose for Firefox and Thunderbird menus looks awfully large on Netbook screens. It wastes space and is visually at odds with reasonably sized content. And for some weird reason you can set the content font and size via the menu but not the font and size for the drop-down menus themselves.

As the "Theme Font & Size Changer" Add-On doesn't work reliably and phones home way too often (showing a nag screen), I dug back into how to do this "manually". Probably a decade after I fixed this the first time...

You need to create the file ~/.mozilla/firefox/*/chrome/userChrome.css with * being your profile directory (<random_number>.default usually) and you most probably have to create the chrome directory first.

The same for Thunderbird resides in ~/.thunderbird/*/chrome/userChrome.css. Here again the chrome directory will most probably need to be created first.

needs to go into these files for Firefox or Thunderbird respectively. The curly braces are important. So copy & paste correctly. Symlinks or hardlinks are fine if those files do not need to differ between your web browser and your email client.

Restart Firefox and/or Thunderbird to see the effect.

Obviously you can choose any other font and font size in the snippet above to suit your taste and requirements.

If you are massively space-confined and don't mind a quite ugly UI, check out the Littlefox Add-on. Ugly but optimal use of the minimal screen estate with very small screens.