Decreasing scale with TGaxis

[pamputt]

Hello,
in ROOT 6.12.06, this code

#include "TCanvas.h"
#include "TGaxis.h"
#include "TPad.h"

#include <iostream>
#include <vector>

void testTGaxis()
{
  TCanvas *c = new TCanvas("c","c");
  TGaxis *newaxis1 = new TGaxis(0.1+gPad->GetUxmin(),
			       1.5*gPad->GetUymax(),
			       1.9*gPad->GetUxmax(),
			       0.5*gPad->GetUymax(),
			       100.,
			       0.,
			       510,"-");
  newaxis1->SetLabelOffset(0.);
  newaxis1->Draw();
  TGaxis *newaxis2 = new TGaxis(0.1+gPad->GetUxmin(),
			       0.2*gPad->GetUymax(),
			       0.9*gPad->GetUxmax(),
			       0.2*gPad->GetUymax(),
			       0.,
			       100.,
			       510,"-");
  newaxis2->SetLabelOffset(0.);
  newaxis2->Draw();
}

gives this figure

As we can see, the first TGaxis is not so good. What I would ike to get is a TGaxis with a decreasing scale (starting from 100 on the left side to 0 on the right side). How to do this? Is it a bug?

[couet]

{
   TCanvas *c = new TCanvas("c","c");
   c->Draw(); c->Update();
   TGaxis *newaxis1 = new TGaxis(0.9*gPad->GetUxmax(),
                                 0.5*gPad->GetUymax(),
                                 0.1+gPad->GetUxmin(),
                                 0.5*gPad->GetUymax(),
                                 0.,
                                 100.,
                                 510,"");
   newaxis1->SetLabelOffset(0.05);
   newaxis1->Draw();
   TGaxis *newaxis2 = new TGaxis(0.1+gPad->GetUxmin(),
                                 0.2*gPad->GetUymax(),
                                 0.9*gPad->GetUxmax(),
                                 0.2*gPad->GetUymax(),
                                 0.,
                                 100.,
                                 510,"-");
   newaxis2->SetLabelOffset(0.);
   newaxis2->Draw();
}