Use app information about window drawable changes for desktop sharing?

[Sławomir Lach]

I hear that VNC is ineffective and many Wayland compositors implement only 
this approach. I do not know Wayland internals well, so be polite :-( .

I do not known if wayland have already protocol for deal, which part of window 
were updated om last frame.

If does, could Wayland allow to receive this information by screenrecorder/
desktop sharing app? It could made thinks like in RDP possible for screen/
desktop sharing on Linux.

I think there is no need to implement this in each application - only toolkit 
will be involved. If app do not use toolkit, it were forced to implement this 
by itself or desktop sharing app would update whole window on client side on 
each frame (fallback).
Wayland would only look if app send information about part, which was updated, 
on last frame. If not - it inform, that whole window was updated. But if app 
send info, it bypass it. After bypassing this information, wayland will clear 
buffer of updated regions for each window.

Best regards,
Sławomir Lach.