There are several ways of deleting objects from a pad in batch mode.
Assume a pad created with the following objects:
 TCanvas c1("c1")
 TLine *line1=new TLine(.1,.1,.9,.7)
 line1.Draw()
 TLine *line2=new TLine(.1,.8,.8,.2)
 line2.Draw()
 TBox *box1=new TBox(.2,.2,.5,.4)
 box1.SetFillColor(42)
 box1.Draw()
You can:
  a, Delete all objects from a pad
     c1->Clear();
  b, Delete some objects 
     delete line1;
     delete line2;
     c1->Modified();
     c1->Update();
  c, keep the objects alive, but remove them from the pad
     TList *glist = c1->GetListOfPrimitives();
     glist->Remove(line1);
     glist->Remove(box1);
     c1->Modified();
     c1->Update();
 
> Another problem occured when I tried to convert a TCanvas into a postscript
> file. Everthing worked as it should, only when using a shaded contour plot the
> whole output is getting messed (so now I don't use it...).
> 
Could you tell me which fill color and fill style was used?
Some pattern styles are emulated under Postscript and may be
quite slow to print.
> And just a remark or the THtml class. I really love it =8->. But I really tried
> hard to get the automatic documentation running in a program which is linked.
> After a quite while I found out that you have to init first a TApplication,
> before you can define your THtml. This was not clear to me in advance! Perhaps I
> did not read the documentation carfully enough, but I did not find any
> references to that....
To generate the html documentation for a class, you must
generate the dictionary. See the root/test/Event example
how to generate a dictionary.
To generate the documentation, do:
   THtml html;
   html.MakeClass(classname);
Rene Brun