Hi,
I just received an e-mail as an answer to the question below, which made me
'investigate' some more.
>Furthermore, I was wondering about the something associated for drawn
>objects. I've been rereading the ROOT-documentation ("Overview") and I
>found the follwing, on page 35 How to Draw Objects:
>
>An instruction Object->Draw() in fact does not draw directly. It simply
>adds a reference (...) This means that if the content of object changes,
>your picture will change.
>
>This is not true, at least not for "stack" based TH1F and TF1. (I didn't
>check how it exactly works with heap based ones.)
It turned out that one has to call Modified(1) of the canvas in which the
Histogram appears. In command-line mode, this result in an automatical
update of the canvas, since the Update() methods of the canvases are called
after execution of each line. I can image the want for the Modified flag
for object which are IN the canvas, but for the canvas itself this seems a
bit strange, since the call MyCanvas->Modified(1) apparently (ALWAYS) needs
to proceed a call to MyCanvas->Update(), to force the update of the canvas.
I don't know about the technicalities, but I would propose to either set
the Modified flag of a canvas to kTRUE every time something in the canvas
is modified or to arrange that a call to Update always checks the Modified
flags of the drawn objects (regardless of the Modified-flag of the canvas).
Does anyone disagree???
Ciao,
Marco van Leeuwen
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