In TCanvas "option" menu, if "Event Status" is selected, coordinate
 information can be shown at the bottom of the Canvas. It's something like 
the following exmple:
   Pad example      TFrame   122,333,   x=1.97,y=3.06
In above example, "x" and "y" give the position  of your mouse in 
a TFrame that contains the histogram. Could you tell me how to 
get the value of "x" and "y" in my code. 
I did not manage to find answer in the source code of TCanvas.
Sincerely yours
Xie