Setting a default browser in i3
The problem
I've been using the excellent qutebrowser for a few weeks now and I really enjoy it's minimal approach to web browsing. I still reach for Firefox or Chrome for web development purposes but qutebrowser shines as a daily driver. An issue I ran into is I didn't know how to set qutebrowser as my default web browser when using i3wm (or any tiling window manager really).
The Solution
Here's the solution if you don't care about the process of figuring it out:
xdg-settings set default-web-browser org.qutebrowser.qutebrowser.desktop
The Yak
Thankfully there's an issue on the qutebrowser repo where folks discussed this very thing. Let's pull the solution apart to gain some understanding of the systems at play here.
The first part of the solution in the issue thread is:
ls /usr/share/applications/ | grep qutebrowser
which lists all the files in /usr/share/applications and then greps that list for entries that contain the word qutebrowser. The Arch Wiki entry on "Desktop entries" explains what the files inside /usr/share/applications are and why that directory is important.
Desktop entries for applications, or .desktop files, are generally a combination of meta information resources and a shortcut of an application. These files usually reside in /usr/share/applications/ or /usr/local/share/applications/ for applications installed system-wide, or ~/.local/share/applications/ for user-specific applications.
So by looking for qutebrowser in /usr/share/applications we're looking for its .desktop file which is important for the next step.
Looking at the next part of the solution involves running a program called xdg-settings. What is that? The man page declares that xdg-settings is used to "get various settings from the desktop environment". OK, so it's a tool to get (and apparently set?) desktop environment settings. This seems like the right thing. Let's keep reading the man page.
Further on in the man page we find an example on how to set Chrome as the default web browser: xdg-settings set default-web-browser google-chrome.desktop. Notice the .desktop file at the end of the command? XDG uses that file name to figure out which app to use for certain file and link types like text/html or x-scheme-handler/http. Back to our specific case, we need the full name of the desktop file to pass to xdg-settings which is org.qutebrowser.qutebrowser.desktop. With this information we can change the default browser to qutebrowser by running:
xdg-settings set default-web-browser org.qutebrowser.qutebrowser.desktop
This tells the desktop environment to launch whatever process is defined in that .desktop file for "browser things".