Hi Rene,
> Simply derive your painter from the existing painter
> and redefine only one or a few functions.
yes, but then you change behaviour of ALL histograms.
But what to do if you want to change it only for one?
When Painter is a separate class, it is very natural
to allow to Paint different histograms by different painters.
Victor
Rene Brun wrote:
>
> Hi Victor,
> You do not need to reimplement a complete painter.
> Simply derive your painter from the existing painter
> and redefine only one or a few functions.
> In a separate mail from Fons (that did not reach roottalk), he says:
> > we clearly did not describe clearly enough how to derive from
> > TVirtualHistPainter or from THistPainter and how to make your new
> > painter the default painter.
> >
> > Assume you want to modify the existing default THistPainter:
> >
> > - class TMyHistPainter : public THistPainter { ... };
> > override only the few paint methods you want to change
> >
> > - compile into a shared lib libMyHistPainter.so
> >
> > - in rootlogon.C add the following:
> >
> > > // make sure the base class is loaded
> > > gROOT->LoadClass("THistPainter","HistPainter");
> > > gROOT->LoadClass("TMyHistPainter", MyHistPainter");
> > > TVirtualHistPainter::SetPainter("TMyHistPainter");
> > >
> > > - from now on all histograms will be painted using the new
> TMyHistPainter.
> > >
>
> Rene Brun
>
> On Thu, 21 Oct 1999, Victor Perevoztchikov wrote:
>
> > Hi Rene,
> >
> > > Once this is called (once per job), TH1::Paint will automatically
> > > invoke your painter.
> >
> > no, it is good only if user does not want standard Painter at all.
> > But usually standard painter is good enough, but for very special
> > histograms, user wants provide modified painter do NOT AFFECTING all others histograms.
> > For this case method SetPainter() is very usefull and safe.
> > And it is very easy to implement, just 3 lines of code and no more discussion
> >
> > Victor
> >
> >
> > Rene Brun wrote:
> > >
> > > Hi Victor, Damir,
> > > There is no need for TH1::SetPainter
> > > You can directly use the static function
> > > TVirtualHistPainter::SetPainter(const char* myPainterClassname)
> > > Once this is called (once per job), TH1::Paint will automatically
> > > invoke your painter.
> > > Note that each histogram has its own painter instance in such a way
> > > that the system can work in a multithreaded environment.
> > >
> > > Rene Brun
> > >
> > > On Thu, 21 Oct 1999, Victor Perevoztchikov wrote:
> > >
> > > > Hi Damir,
> > > > in new TH1 class no method SetPainter(TVirtualHistPainter *userPainter);
> > > > If Rene & Fons will add it, then you can create your painter
> > > > object derived from TVirtualHistPainter and set it to histogram.
> > > >
> > > > As a temporary solution you can use the following "barbaric" function
> > > > to add your method to histogram. When rene will add SetPainter to TH1
> > > > then you can remove it.
> > > >
> > > > void SetPainter(TH1 *h,TVirtualHistPainter *p)
> > > > {
> > > > TVirtualHistPainter **s = (TVirtualHistPainter **)((int*)h+117);
> > > > p->SetHistogram(h);
> > > > *s = p;
> > > > }
> > > >
> > > > Victor
> > > >
> > > > "Valeri Fine (Faine)" wrote:
> > > > >
> > > > > ----- Original Message -----
> > > > > From: Valeri Fine (Faine) <fine@bnl.gov>
> > > > > To: Damir Buskulic <buskulic@lapp.in2p3.fr>; ROOT mailing list <roottalk@hpsalo.cern.ch>
> > > > > Subject: Re: painting an object derived from TH1
> > > > >
> > > > > ----- Original Message -----
> > > > > From: Damir Buskulic <buskulic@lapp.in2p3.fr>
> > > > > To: ROOT mailing list <roottalk@hpsalo.cern.ch>
> > > > > Subject: painting an object derived from TH1
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > with the new library scheme of ROOT, the Painter and Hist are separated.
> > > > > > I have a class that derives from TH1F, but I would like to paint some
> > > > > > parts differently, namely the stat box. Before, I was just overloading
> > > > > > the TH1::PaintStats method.
> > > > > > How can I do it now ? Do I have to specify a completely different
> > > > > > painter that I have to rewrite ? I looked a little bit at the code and
> > > > > > found that the static member fgPainter was holding the class description
> > > > > > of the current Painter. Since it is static, I cannot change it without
> > > > > > changing also the painter for regular TH1.
> > > > > > I suppose I'll just put regular stats off and overlay my own stat box.
> > > > > >
> > > > > > Any other ideas ?
> > > > >
> > > > > I missed one essential point, one has to add
> > > > > fPainter->StHistogram(this) ;
> > > > > statement to get:
> > > > >
> > > > >
> > > > > class TMyHist : public TH1 {
> > > > > public:
> > > > > TVirtualHistPainter * Painter(TVirtualHistPainter *myPainter) {
> > > > > TVirtualHistPainter * old = fPainter;
> > > > > fPainter = myPainter;
> > > > > if (fPainter) fPainter->SetHistogram(this) ;
> > > > > return old;
> > > > > }
> > > > > }
> > > > >
> > > > > Afterwards you can define your own painter and attach it to your particular
> > > > > histogram. This way you may use either standard or your own Painter with each
> > > > > other Update step or for different TPads.
> > > > >
> > > > > Another solution:
> > > > >
> > > > > class TMyHist : public TH1 {
> > > > > public:
> > > > > TVirtualHistPainter * Painter(TVirtualHistPainter *myPainter) {
> > > > > delete fPainter; fPainter = 0;
> > > > > if (myPainter) {
> > > > > fPainter = myPainter;
> > > > > fPainter->SetHistogram(this) ;
> > > > > }
> > > > > return fPainter ;
> > > > > }
> > > > > }
> > > > >
> > > > > Valery
> > > >
> > > > --
> > > > Victor M. Perevoztchikov perev@bnl.gov perev@vxcern.cern.ch
> > > > Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000
> > > > tel office : 516-344-7894; fax 516-344-4206; home 516-345-2690
> > > >
> >
> > --
> > Victor M. Perevoztchikov perev@bnl.gov perev@vxcern.cern.ch
> > Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000
> > tel office : 516-344-7894; fax 516-344-4206; home 516-345-2690
> >
--
Victor M. Perevoztchikov perev@bnl.gov perev@vxcern.cern.ch
Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000
tel office : 516-344-7894; fax 516-344-4206; home 516-345-2690
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