[Mono-dev] libgdiplus drawing performance

[Martín Vales]

Shade1974 escribió:
> First, let me say, I have been really excited about the mono project and am
> an enthusiast on the grounds that it potentially might allow us to take our
> C# programming multi-platform.  We are developing a C# application that
> needs to draw thousands of separate lines.  I have been having trouble with
> getting drawing to work quickly.  This is one of those unfortunate scenarios
> where it seems almost impossible to Google anything useful, and it took a
> long time before I discovered that you could group thousands of lines
> together into a single drawing path and draw them all at once with a single
> call to the graphics device (GDI+ API).  This is on the order of THOUSANDS
> of times faster, not merely one or two times as fast.  Now, imagine my
> distress after having implemented this blazingly quick drawing in windows
> only to discover that MONO seems to be unable to duplicate this
> optimization.  I believe that the problem originates because the managed
> mono wrapper must take the single DrawPath instruction and sub-divide it
> into the individual calls to the API.  This might be necessary when talking
> to Cairo, but I thought on windows this was simply supposed to forward the
> instructions to GDI+.  The fact that even the windows implementation is slow
> tells me that it's possible that the authors simply didn't know that there
> was a huge performance gain by calling a chunky DrawPath instead of chatty
> individual calls, or else they would at least have supported it in the case
> of windows.
>
> Anyway, like I said it took a huge amount of time before I even figured out
> the optimization in the first place and I have just started to work with
> mono.  It's quite probable that I am overlooking something straight forward,
> but I'm having trouble figuring out what it is.  If anyone knows some
> information that could help I'd be grateful.
>
> Shade1974
>
>   
I believe gdi+ in linux is not optimized to a CAD because is a emulation 
of the p/invoke gdiflat API using cairo and parts of the libgdi is not 
optimized:
http://msdn.microsoft.com/en-us/library/ms533969(VS.85).aspx 
<http://msdn.microsoft.com/en-us/library/ms533969%28VS.85%29.aspx>

For graphical interfaces is nice but perhaps you need use opengl with 
mono and .NET.
http://mono-project.com/Tao

or use agg-sharp is a full port of antigrain library to c#:
http://sourceforge.net/projects/agg-sharp

-- 
Martín R. Vales,
Intergeo Tecnología (IGT)
El Escorial (Madrid)
__
www.intergeotecnologia.com