Need an xdg-email wrapper, similar to the xdg-open one

[Olivier Tilloy]

The chromium snap has some magic to symlink /usr/bin/xdg-email to /usr/bin/xdg-open to work around bug #1849774. This is because chromium invokes xdg-email when a mailto: hyperlink is clicked.

That magic works in most cases because xdg-open generally knows how to handle mailto: links, but apparently there are corner cases where it doesn't, which is why xdg-email should be used (see https://bugs.chromium.org/p/chromium/issues/detail?id=61942).

I suppose chromium is not an isolated case, other applications might want to call xdg-email to offer users to compose a new e-mail with their preferred e-mail client.

Can snapd expose an xdg-email wrapper (that would accept only mailto: links), similar to the existing xdg-open wrapper?

[Zygmunt Krynicki (zyga)]

Without knowing more about the problem, would using the existing xdg-open program for xdg-mail? Currently the xdg-open program inside snap mount namespace does support mailto: URL scheme. Could we simply provide a symlink from xdg-mail to xdg-open?

[Olivier Tilloy (osomon)]

This would work in the general case, but not always. xdg-open special-cases some well-known desktop environment (e.g. GNOME, KDE, XFCE), and for those it would work. But other more obscure DEs may not expose what xdg-open needs to handle mailto: links, which I guess is why xdg-email exists in the first place. There are details in the chromium bug I shared in the description.

So symlinking xdg-open to xdg-email would definitely be an improvement over the existing situation, but not a complete solution.

[Zygmunt Krynicki (zyga)]

I understand. I will raise this topic with the desktop team.

[James Henstridge (jamesh)]

From a look at the xdg-email man page, it looks like it maps fairly well to the org.freedesktop.portal.Email.ComposeEmail method call.

Given that we want to switch the sandbox xdg-open over to preferring the xdg-desktop-portal API over userd, I think an xdg-email proxy should target the portal API exclusively rather than add a new userd API.

[James Henstridge (jamesh)]

One thing that would be worth trying from the sandbox side: the flatpak-xdg-utils package contains an implementation of xdg-email that calls into xdg-desktop-portal. Any xdg-email proxy provided to snaps would look very similar to this.

Flatpak-xdg-utils is not packaged in xenial or bionic, but it looks like it would be fairly simple to build from source within e.g. the Chromium snap:

https://github.com/flatpak/flatpak-xdg-utils

[James Henstridge (jamesh)]

On further investigation, this probably isn't suitable for Chromium (yet), since it doesn't seem to support mailto: URIs yet:

https://github.com/flatpak/flatpak-xdg-utils/issues/19

[Ian Johnson (anonymouse67)]

The associated flatpak-xdg-utils issue was closed, perhaps the chromium snap can start building that now?