Developing applications expected to run over RDP; any tips ?

Question

Supposing I was developing a fairly graphically intensive application (C++ or C#, graphics API undecided) for which most of the usage will be by remote users over RDP (either terminal server sessions or remote access to a single-user machine). It's obvious that non-essential "eye-candy" effects and animations should be avoided. My questions are:

• What should I be careful to do/avoid doing to make most efficient use of the RDP protocol ? (e.g I have an idea RDP can remote some graphics drawing primitives straight to the client... but is that only for GDI ? Does using double-buffering break such remoting and force a bitmap mode ? Does the client-side bitmap cache "just work" or does it only cache certain things like fonts and icons ?)

• Is there any sort of RDP protocol analyser available which will give some insight into what an RDP stream is actually transporting (in particular, bitmaps vs drawing primitives) ? (I can imagine adding some instrumentation to the rdesktop source to do this, but maybe something exists already).

Answer 1

My idea is that the optimization work made on RDP already cover 90% of the problem you're describing, so I would not worry about optimizing for RDP, you're already removed the eye-candy stuff, you know that the application will be used via RDP so I suppose you'll avoid operations that involves continuous redrawing of form, I believe that sould be enough.

Our application was never designed with RDP in mind, we had the same worries you have when a customer told us that all its client will be used via RDP (Citrix, in that specific case) from remote locations but also if we didn't change a single line of code the customer never called with slowlyness problems due to RDP.

Remember... Premature optimization is evil.

Answer 2

In my experience I'd be careful when it comes to animations - especially fade up/down controls that can seriously kill performance over RDP.

Double-buffering might also cause some problems, however I personally haven't had to do too much in the way of workarounds for this - the article by Raymond Chen explains the possible pitfalls quite well.

Essentially, it's a good idea to check in code whether it's running in a remote sessions (RDP, Citrix, etc). Take a look at: GetSystemMetrics( SM_REMOTESESSION ) - you can then decide at runtime whether to enable or disable certain features.