Integrate Webcam Function with "Qubes Devices" System Tray Menu

[ElliotKillick]

Having the webcam functionality integrated into the Qubes Devices system tray menu would lead to a much better user experience for using a webcam in Qubes OS.

Note that this would still leave the screen sharing functionality of Qubes Video Companion with no GUI to use with. A special GUI application would probably have to be made for the screen sharing functionality as that has nothing to do with devices and has a much different architecture. Where sharing a webcam is a one-to-many sharing operation; sharing screens would be a many-to-many relationship because each VM has its own screen which they can share while also receiving the screen of another VM.