Re: [ROOT] RE: zoomed in TGraph bug

From: Rene Brun (Rene.Brun@cern.ch)
Date: Wed Feb 27 2002 - 13:00:58 MET


Hi Tony,

Did you start from the CVS source with the tag 3-03-02 or from
the CVS head? I implemented this change only last night !

This morning, I have added additional protections in TGraph::ExecuteEvent
in case you zoom with very large factors.

Rene Brun

Colley, Tony wrote:
> 
> By the way, I just did a CVS update, remade & reinstalled ROOT, and now am
> running ROOT 3.03/02...
> 
> and the problem described below still exists.
> 
> -----Original Message-----
> From: Colley, Tony
> Sent: Tuesday, February 26, 2002 15:37
> To: 'ROOT Talk'
> Subject: zoomed in TGraph bug
> 
> The following demonstrates a "minor" bug in TGraph:
> 
> {
> Int_t i;
> Float_t x[1000];
> Float_t y[1000];
> 
> for (i=0; i<1000; i++)
> {
>    x[i] = 0.001*i;
>    y[i] = 6.2831853*x[i];
>    y[i] = sin(12*y[i]) + sin(17*y[i]) + sin(56*y[i]) + sin(74*y[i]);
> }
> 
> TGraph *graph = new TGraph( 1000, x, y );
> graph->Draw("AL");
> 
> printf(
> "\n\n===============================================================\n" );
> printf( "Right click on X axis and select SetRangeUser.\n" );
> printf( "Enter the range 0.387 to 0.389 and click OK.\n" );
> printf( "Move the cursor over one of the 3 points (at .387, .388, .389).\n"
> );
> printf( "Press down the left mouse button.\n" );
> printf( "When I do it, there are 6 extra boxes drawn\n" );
> printf( " (in addition to the three that should be drawn)\n" );
> printf( "===============================================================\n"
> );
> }
> 
> (I've attached the same thing as tgdemo.C, in case that's easier to use than
> just cutting/pasting from this email)
> 
> The y function was chosen arbitrarily. The bug appears for many other
> functions I tried.
> 
> The bug is even more insidious when you significantly increase the number of
> data points graphed. When you zoom in close enough to begin seeing
> individual points, in addition to having many extra boxes, some boxes are
> apparently drawn too close to the edges because there is a wraparound effect
> (giving rectangles spanning the graph rather than little boxes around the
> points).
> 
> I also noticed in the example I provided, if you don't zoom in quite so far,
> there are extra boxes drawn extending out of the left and right sides of the
> graph. These boxes seem to correspond to data points outside the graph
> clipping area but within the canvas clipping area. I'm not sure if I would
> classify this behaviour as a bug or a feature... it could be useful and may
> be intentional (i.e. a feature).
> 
> Tony Colley
> ITT Industries A/CD
> Fort Wayne, IN  USA
> 
> Using ROOT 3.03/00, last updated from CVS on 18 Feb 2002, on RedHat Linux
> 7.2
> 
> ************************************
> If this email is not intended for you, or you are not responsible for the
> delivery of this message to the addressee, please note that this message may
> contain ITT Privileged/Proprietary Information.  In such a case, you may not
> copy or deliver this message to anyone.  You should destroy this message and
> kindly notify the sender by reply email.  Information contained in this
> message that does not relate to the business of ITT is neither endorsed by
> nor attributable to ITT.
> ************************************



This archive was generated by hypermail 2b29 : Sat Jan 04 2003 - 23:50:43 MET