if 0 {[Richard Suchenwirth] 2003-11-19 - Here is how to move nodes on a [BWidget] [Tree] widget. When you click on a node's text, a movable copy of the text is added and follows the mouse motion. When you release the mouse button on another node, the "moving" node is indeed moved to be the first child of that node (if possible - one can't reparent into a descendant).
}
 package require BWidget

 proc tree'mark {w x y label} {
    set text [[winfo parent $w] itemcget $label -text]
    $w create text $x $y -text $text -tag marked
    set ::g(x) $x
    set ::g(y) $y
 }

 proc tree'motion {w x y label} {
    $w move marked [expr $x-$::g(x)] [expr $y-$::g(y)]
    set ::g(x) $x
    set ::g(y) $y
 }
 proc tree'release {w x y label} {
    $w delete marked
    if [regexp n:(.+) [$w gettags [$w find closest $x $y]] -> target] {
	if {$label ne $target} {
	    set tree [winfo parent $w]
	    catch {
		$tree move $target $label 0
		$tree opentree $target
	    }
	}
    }
 }
#----- testing demo:
 pack [Tree .t]

 .t insert 0 root node1 -text hello
 .t insert 0 root node2 -text world
 .t insert 0 root node3  -text again
 .t insert 0 node2 node4 -text fourth

 .t bindText <1>               {+ tree'mark %W %x %y}
 .t bindText <B1-Motion>       {tree'motion %W %x %y}
 .t bindText <ButtonRelease-1> {tree'release %W %x %y}

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[Arts and crafts of Tcl-Tk programming]