Explicit clipboard mode

[robertvazan]

The 4 clipboard modes currently implemented involve hard tradeoffs between usability and security. I propose adding fifth clipboard mode, let's call it Explicit, that would behave like QubesOS clipboard.

In Explicit clipboard mode, no clipboard contents would be shared by default. User could however press a keyboard shortcut to transfer clipboard host->guest or guest->host for the currently focused VM.

Proposed default shortcuts:

• host -> guest: Ctrl+Shift+V
• guest -> host: Ctrl+Shift+C

New workflow:

• host app -> guest app: Ctrl+C, focus VM app, Ctrl+Shift+V, Ctrl+V
• guest app -> host app: Ctrl+C, Ctrl+Shift+C, focus host app, Ctrl+V

This should be easy to implement and yet very valuable for people who routinely use VMs as a secure sandbox.

Note that this is not the only way to streamline clipboard without compromising security. For example, one other option is to tie clipboard transfers to well-known shortcuts, i.e. to perform host->guest transfer before Ctrl+V and guest->host transfer after Ctrl+C. Let's call this other mode Smart or Automatic. It's harder to implement though, because there are more shortcuts to consider and they vary between platforms.