El 31/10/2012 10:13, Michael Schnell escribió: > I understand that there are (at least) two ways to do the remote display. > > A) Read the pixels from the graphics driver. This is what VNC does. > The problem here is, that you don't know when an update is necessary > (and thus you need to do polling) and that reading the pixels needs a > lot of performances (get a GDI-handle, read the complete screen memory > via the bus and then transfer only the pixels that have changed). (In > fact some time ago I stole this code from VNC, translated it from C to > Pascal and did a thingy that could transfer a rectangle of the screen > via TCP to another PC.) > > or > > B) Hook into the interface between the application and the Windows > manager. This is what Linux "Remote X" and Windows "Remote Desktop" > do. VirtualBox (and supposedly VMWare) seems to be able to do do this, > too, and here I did already see that it is possible to virtualize a > single program rather than a complete Desktop. > > > > Seemingly NX can do both, depending on the situation.
I suppose that NX not only compress, but decides from the server (in behalf the client application) what must be send to the client (the graphic server). A lot of things needn't to be send, a lot of things can be joint and send only the final result, and a lot of commands can be queued, cached and sent in less commadds. And the other way around, the client (the graphic server) needent to sent everything. I suppose that NX does smart decisions filtering what needs to be sent in both directions, so saves a lot of traffic and round trips. X11 It is acceptable when in a local machine, but not for remote machines, let alone a WAN. I've heard that the problem is in a poor use of X11 of libraries like gtk or qt, I've also heard that the problem is in xlib, the common libarry of most widgets that doesn't optimize the protocol. I have also heard that X11 is a too low level protocol and should be replaced. There have been some tries like http://en.wikipedia.org/wiki/Fresco_%28windowing_system%29. In fact, that is what javascript and ajax tries, send widgets etc. -- Saludos Santiago s...@ciberpiula.net -- _______________________________________________ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus