Re: Gnuplot win terminal regression

[Ethan A M. <merritt@u.washington.edu>]

On Wednesday 03 September 2008, Bastian Maerkisch wrote:
> I found out what's happening:
> 
> In case of "lt palette z" and "lc rgb variable" there's a
> polygon with the same start and endpoint. 

How does that happen?  Is this the real bug?

> Windows optimizes this away  
> and the drawing position is not updated. The next call to W_vect
> therefore uses the wrong starting point.
> 
> Possible fixes:
> a) a MoveTo() at every W_move call
> b) a MoveTo() after all Polyline calls
> c) filter out such polygons and replace by calls to MoveTo()
> 
> 
> I'd prefer option b) because it is straightforward and does not 
> introduce many additional GDI calls:
> 
> 	if ((lastop==W_vect) && (curptr->op!=W_vect)) {
> 	    if (polyi >= 2) {
> 		Polyline(hdc, ppt, polyi);
> 		MoveTo(hdc, ppt[polyi-1].x, ppt[polyi-1].y);  /* make sure we move the 
> drawing position in case of empty polygons */
> 	    } else if (polyi == 1)
> 		LineTo(hdc, ppt[0].x, ppt[0].y);
> 	    polyi = 0;
> 	}

I don't understand why that would fix it, as it still looks to me from
reading the code that every move command has the potential to trigger 
the (polyi == 1) case.   But if you have tested it, then fine.

	Ethan 


> 
> 
>    Bastian
> 
> 
> Ethan A Merritt schrieb:
> > Bastian:
> > 
> > Back in June I applied a patch from you that had the following ChangeLog
> > entry:
> > 
> > 2008-06-24  Bastian Maerkisch  <bma...@we...>
> >         * src/win/wgraph.c (drawgraph): Don't forget to draw a polyline even
> >         if it has only a single segment.
> > 
> > There is now a report on the newsgroup that for data files containing 
> > multiple polyline definitions (e.g. blank lines in the file), each supposedly
> > independent polyline is connected to the previous one.  From inspection of
> > the code, I conclude this is due to your change above.  That is, the initial
> > move command sets polyi=1, but your change causes this to be treated as a
> > length 1 polyline rather than a move.   Strangely, this happens only for
> > plots with either "... lc rgb variable" or "... lt palette z".
> > I don't fully understand why the linetype makes a difference.
> > 
> > Could you have another look at this issue please?  Perhaps the previous
> > patch should be reverted, or perhaps an additional fix is needed somewhere
> > in the W_pm3d_setcolor code block in wgraph.c.
> > 
> > I'd like to release an incremental version 4.2.4 sometime soon, and this
> > is the only regression I know of that would hold it up.
> > 
> > 	Ethan
> > 
> 
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
> Build the coolest Linux based applications with Moblin SDK & win great prizes
> Grand prize is a trip for two to an Open Source event anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> gnuplot-beta mailing list
> gnu...@li...
> https://lists.sourceforge.net/lists/listinfo/gnuplot-beta
> 



-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742