canvas .c1
bind .c1 <Double-1> { onDblClick %x %y }
proc onDblClick {x y} {
        set x [.c1 canvasx $x] ; set y [.c1 canvasy $y]
        set i [.c1 find closest $x $y]
        set t [.c1 gettags $i]
        puts "$i $t"
}