Add virtual keyboard to Tails Greeter

Originally created by Tails on #5563 (Redmine)

In order to protect users against encryption passphrase and sudo password compromise in the presence of a hardware keyboard logger, the Florence Virtual Keyboard should be available in Tails Greeter.

Implementation research

A proof of concept has been implemented :

• add florence.desktop to gdm greeter session
• florence needs a system tray to enable user to access its icon, so, install trayer and add a corresponding .desktop to gdm greeter session.

This works, but a solution which does not require to display another panel has to be found.

Why do we "have" to find another solution? If we really have, how hard would it be to have the existing tails-greeter panel act as a system tray?

Potentially interesting links

• Using Florence with GDM

Related issues

• Related to #7500 (closed)
• Related to #10041 (closed)
• Related to #10814 (closed)
• Related to #12385 (closed)
• Has duplicate #5783 (closed)
• Has duplicate #5587 (closed)
• Blocks #6064 (closed)