Dear Valeri, Brett & the Rooters, sorry about the mess around gPad, I guess it was not very clear to me what would be the best approach. I vote for 2) to be solved first... I agree also with Valeri about where to emit the signal. I think this would solve my problem, since each time something is added to a Pad there is a method called to repaint the pad/canvas. In my case, gPad is the most important pointer since it tells me what the user is looking at... and then from which pad I should retrieve automatically the data. Fred > There could be several different "points of view" > > 1. One wants to get a signal when some object data-member is changed. > It is interesting (and very useful) but it has nothing to do with the GUI, > TPad, gPad, TCanvas etc. > By this reason I think we should decouple such sort of "modification" of the > TPad modification issue. I think TPad itself can not do this. > It is difficult to find a generic solution. > > 2. Some TPad (why gPad ?) modified when its appearance on the "screen" has been changed. > My guess many GUI applications would be happy to know very this moment. > Now this has nothing to do with the objects those has been appended to > the TPad. This moment is well defined by ROOT and can be caught. > To change the image of the TPad on the TCanvas screen the method > TPad::CopyPixmap is to be called . That in turn calls gVirtualX->CopyPixmap. > So TVirtualX::CopyPixmap can signal when the image on the screen is about to > be changed. > > Now we have to split our discussion, create two different brainstorming teams and vote :-). > What do most of us are speaking about. Is it case 1) or 2) > > Myself scare to join the first team and think it would be not too difficult to resolve > the second issue. > > Best regards, Valeri > > ----- > Dr.Valeri Fine > STAR/US Atlas E-mail: fine@bnl.gov > Brookhaven National Lab Phone: +1 631 344 7806 > Upton, NY 11973-5000 FAX: +1 631 344 4206 > USA
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