[Kst] Curve polygons

[Brisset, Nicolas]

Hi Peter,

nice to see you're still around, and taking care of kst under Windows :-) 

I agree that kst 2 is unfortunately pretty broken under Windows. Right now, I've had to revert to an older version as the last trunk exhibits a pretty bad bug - under Windows only - (as reported in bugzilla under http://bugs.kde.org/show_bug.cgi?id=225347). Maybe this is even the same problem? I have not yet tested Qt 4.6.2 and the problem you're reporting is new to me, however: I can plot basic curves without problems.

One possibly related thing I saw yesterday when demoing kst 2 to a colleague who had not been using it yet is that if you disable OpenGL (kst settings) the bad flicker we were seeing went away. It was only flicker, the curves were still there. But maybe with slight variations of the config/OpenGL driver it can lead to the problem you describe. Our observation was done on a PC with a bad graphics board, so probably fairly limited OpenGL performance anyway. Leaving OpenGL disabled is not too bad, but as it is on by default most people would just get pissed off at kst and stop using it. So I consider it to be pretty bad as well!

I don't either see the relationship between your patch and curve drawing. However, there is something I am wondering about. My colleague Grégoire Verlut reported a memleak whereby using many plots and moving the mouse around a lot, he manages to exhaust memory. As far as I know the problem is still there, and if the checkbox you're talking about is the one I think (the one in the upper right corner of each plot, used to toggle tied zoom), then they may be related somehow. The checkbox is being redrawn when changing focus from one plot to the next one. Maybe there is too much being redrawn?

So a couple of concrete questions arise:
1) do you still see the problem if you disable OpenGL?
2) do you also see the problem with older Qt versions (or is it a new regression with 4.6.2)?
3) is it the same bug as the one I have linked above?
4) what happens exactly when the focus changes plots?
5) would it be a good idea to ask on a Qt list or kde-windows about differences between Windows and Linux regarding QGraphics* classes and painting operations?

Nicolas 
 
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-----Ursprüngliche Nachricht-----
> Von: Peter Kümmel [mailto:syntheticpp at gmx.net]
> Gesendet: Donnerstag, 11. März 2010 01:08
> An: kst at kde.org
> Betreff: [Kst] Curve polygons
> 
> At the moment kst is really broken on Windows.
> 
> When a gyrodata curve is drawn the curve is plotted
> but then is immediately erased (Qt 4.6.2).
> Also kst crashes when the window is resized very often.
> After hours of debugging I've found that disabling
> the drawing of the checkBox helps (see patch).
> But this patch makes no sense, the bug must be
> somewhere else.
> 
> I could enable the checkbox when drawing of the polygons
> in curve.cpp, "p->drawPolyline(poly)" is disabled.
> 
> Could it be that the polygons are buggy and somehow irritate
> QPainter?  Is the polygon code bullet proved?
> Or is it a maybe Qt/Windows bug?
> Any Ideas?
> 
> Peter
> 
> 
> 
> Index: src/libkstapp/viewitem.cpp
> ===================================================================
> --- src/libkstapp/viewitem.cpp  (Revision 1101107)
> +++ src/libkstapp/viewitem.cpp  (Arbeitskopie)
> @@ -717,7 +717,8 @@
>          painter->restore();
>        }
>        painter->setBrush(Qt::transparent);
> -      painter->drawPath(checkBox());
> +      //painter->drawPath(checkBox());
>        painter->restore();
>      }
>  #if DEBUG_GEOMETRY
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