I've found what appeared to be a local problem on my windows system
drawing a 50,000 segment polyline to a wxMemoryDC. I was using the
wxDC::Drawlines() function. On Linux the drawing was always fast and
always reproducible. On my windows system, things looked fine provided
the wxPEN had WIDTH=1. As soon as I set the pen width to 2 or more,
everything went pearshaped; the drawing slowed by >  2 orders of
magnitude for <2000 points. For more than 5000 points, the programs
crashed entirely.

I posted a test script a while back (25th Feb 2002) and other users
reported no problems on their WinNT system (I was using win98), so I
think it might be a bug in my graphics-card driver, or the card itself
(I guessing here!).

I can't test your script as I don't have weave installed. If you post a
non-weave version, I'll happily test it on linux.

Bryan

On Tue, 2002-04-30 at 05:06, Robin Dunn wrote:
>  >
>  > All this background to ask some non-wxPython questions (though
>  related...):
>  >
>  >     1.  Can anyone verify that they get the same behavior with
>  >         DrawLines?  <I wondering if something is strange about
>  >         my machine setup>
>  
>  I always get between 0.25 and 0.60, depending on how much area needs
>  refreshed.
>  
>  >     2.  Does anyone have any insight into what is going on here?
>  >
>  
>  Not really.  There is some (probably) unnecessary overhead there though.
>  wxPython's DrawLines transforms the sequence into an array of wxPoint
>  objects and then calls the C++ DrawLines.  (On MSW the wxPoint object is the
>  same structure as MSW's POINT so another transform to call Polyline is not
>  needed.)
>  
>  >          a. Why is PolyLine fast for the initial call and slow for
>  >             subsequent calls with a large number of points?
>  >
>  >          b. Why is PolyLine slow for a large number of points?
>  >             Heck, 30000 isn't even all that large of a number.
>  
>  No idea.
>  
>  >
>  >     3.  Does Linux have the same problem?
>  
>  I don't have Numeric installed there, so I don't know.
>  
>  >
>  >     4.  Am I missing an extra call somewhere that would fix all my
>  >         problems?
>  
>  We added DrawLineList to wxPython's DC in 2.3.2 or .1 that doesn't have the
>  transformation overhead described above.  It takes a sequence of
>  (x1,y1,x2,y2) sequences, and optionally a list of pens, and iterates through
>  it calling DrawLine.  You end up with a ton more win32 API calls, but no
>  transformation.
>  
>  --
>  Robin Dunn
>  Software Craftsman
>  robin@[...].com       Java give you jitters?
>  http://wxPython.org      Relax with wxPython!
>  
>  
>  
>  
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-- 
Bryan Cole
Teraview Ltd., 302-304 Cambridge Science Park, Milton Road, Cambridge
CB4 0WG, United Kingdom.
tel: +44 (1223) 435380 / 435386 (direct-dial) fax: +44 (1223) 435382


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