Allow setting open_dispatcher for unknown schemes?

[The-Compiler]

The downloads.open_dispatcher setting allows using something other than xdg-open for opening downloads.

For unknown schemes (such as mailto: links), this currently isn't possible. The only way out for us is using QDesktopServices::setUrlHandler where we could have a handler function spawning something different. The remaining question is what schemes to do this for. I suppose we could expose a config option for those, and have something like ['mailto', 'magnet'] as a reasonable default.

[lelgenio]

I was trying to get mailto: links working with mutt, I ended up with this:

# ~/.local/share/applications/neomutt.desktop
[Desktop Entry]
Name=Neomutt
TryExec=neomutt
Exec=neomutt %U
Terminal=true
Type=Application
MimeType=x-scheme-handler/mailto;

This seems to work for Firefox and my desktop launcher, but not Qutebrowser, and swaymsg exec xdg-open mailto:xxx; neomutt gets launched but not in a terminal.

Running a dummy script that dumps env I figured it was ignoring the Terminal=true line, because it runs with $TERM = linux. So I just did some hacking.

# here terminal is just "exec alacritty -e $@"
Exec=terminal neomutt %U
Terminal=false

I am not necessarily asking for; This is ugly and stupid, but works. If there's a better way lemmino :)

I assume this issue is related to this, the problems also appears if I :spawn xdg-open mailto:xxx instead of clicking a url.

[The-Compiler]

@lelgenio I don't think there's much we can do about that, as the underlying QtWebEngine/Chromium takes care of opening those links at the moment. This issue isn't really related though, it's about configuring dispatchers inside qutebrowser rather than relying on xdg-open.

[The-Compiler]

Relevant QtWebEngine change: Add a new signal "launchExternalProtocol" when launching external url (I744b6ca9) · Gerrit Code Review - unfortunately didn't make it in and seems abandoned.