Mark C. Szigety wrote: > > Rooters: > quick question. i have a pad in which i have drawn a figure (in this > case, the 2-D layout of a detector). i would like to draw other figures on > top of this detector (specifically, trajectories). however, i would like > to draw them one at a time and, thus, every time i hit a button to draw the > next event, i want the old event erased, but the original picture of the > layout to remain where it was. is there a quick way to do this? i just > don't want to redraw the layout every time a user wants to display a new > event. i can think of some solutions, but they are all memory intensive. > any suggestions? > > thanks a bunch, > mark szigety Mark, The Root pad drawing/updating mechanism is fully described at URL: http://root.cern.ch/root/HowtoDraw.html In your case, with the current version of Root, you have the choice between: - clear the pad, draw detector and tracks for each event - draw the detector once. at each new event, remove tracks from the pad list of primitives. The two options are equivalent in performance. In both cases, the detector Paint function and the tracks Paint function will be invoked. The ideal solution (as indicated by Valery) would be to support transparent pads. It is our intention to support this option in the future versions and also (same problem) support for images (gif,etc) as background for a pad. Meanwhile, I suggest you use option 1 above. Rene Brun
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