Remote UI

What is the benefit? Why is this valuable?

Implementation of this epic will allow remoting or also "projection" of a Qt-based UI to a remote client running on another machine somewhere on the network. This is complementary to WebAssembly as a new platform for Qt, since the application keeps running "as is" and only its UI is projected and input events are forwarded.

The below technical information lists RFB/VNC. It was selected in the most commonly used protocol, and a meanwhile an RFC standard

What are the common use cases?

• Remote maintenance, monitoring, support
• companion apps for embedded devices able to show a projected copy of the UI running on the embedded device
• All use cases cover "closed systems" where additional measures are taken to ensure network security

Technical information

Features available via the "Qt VNC Server" Qt add-on are strikethrough

1. Can connect to a running app
2. Does not require changing the application's source code
3. Can be used with a Qt-based app running on desktop platforms
4. Can be used with a Qt-based app running on embedded Linux
5. Can be used with a Qt-based app running on Android 
6. Can be used with a Qt-based app running on a Wayland desktop
7. Can be used with a non-Qt app running on a Wayland desktop
8. Works with QML-based app
9. Works with Qt C++ based app
10. Compliant with the RFB standard (https://datatracker.ietf.org/doc/html/rfc6143), which is basically VNC
11. Can be used with the most popular RFB clients
12. Separate top-level windows can be projected
13. Multiple clients (viewers) can be connected and interact with a projected app
14. Input can be disabled
15. It is possible to query if there is an active connection
16. The projected app can be controlled by the user as if it was running locally. Limitations and deviations should be well documented
17. A dedicated PIN/Password protection is supported. Strong encryption and protection are not needed here, it is rather an "idiot" protection
18. Logging and tracing for compression ratio and payload sent to the networking stack
19. Efficient processing with a minimal impact on app's performance. Better or comparable with existing VNC servers.
20. The first version is needed as TP for Qt 6.4
21. None to no effort to be backported to Qt5 by "regular" Qt developers who are not Qt-insiders
22. Client-side API or a module to embed a projected view in a Qt app
23. Server-side protocol wrappers allowing novnc-alike viewing via a browser with zero deployment