On Tuesday 25 March 2008 18:43, MacArthur, Ian (SELEX GALILEO, UK) wrote:
> > Both environment show me that 1.1.7 works better
>
> Be careful though - although 1.1.7 is quicker for your specific test
> case, there are many places where 1.1.8 is improved over 1.1.7, so you
> are *probably* better off using 1.1.8 overall.
>
Hmm, I wrote a wrong thing: 

I wanted to say:  
"Both environment  show me that fltk 1.1.8 works better without Xdbe support",
and in fact performance without Xdbe support are very similar for 1.1.7 and 
1.1.8.

Effectively I was using 1.1.8 but at some point I noticed that maximixing
a double window have had the background black for few seconds,
a thing that I don't see normally  ... 

Than, I started some investigation, ending up isolating the problem
around the Xdbe feature.

After that I looked at Fl_Double_Window.cxx source, 
(without a deep knowledge of both Fltk internals and X libraries):
among other things the only significative changes I'm able to see
(related to this issue) is a "copy" flag that is present in 1.1.7
and not in 1.1.8.

The "copy" flag is around the code ".... XdbeSwapBuffers  ; return ..."

Not sure, but it look like a 1.1.7 Xdbe bug, (where XdbeSwapBuffers mostly is 
not used, even if available, therefore hiding the bad performance of 
XdbeSwapBuffers).

I end up disabling Xdbe, and using 1.1.8,
 
but I think that if this is a common situation user and developers should be 
warned about. 
Altought my example was an artifact, nothing of practical use,
it showed me that without Xdbe speed was about 3 times
than with Xdbe on my systems.

Regards

Andrea