Well, I think we can start with a botanical metaphor ...If we think at a bw-tree as a live tree, we could start thinking at a dried-tree as a synthetized clone of a bw-tree, i.e. a new kind of a copy of (a part of) a bw-tree.This dried-tree is not a bw-tree; it is a derived from a bw-tree, but it cannot be handled with the usual bw-tree methods.But there are many things we can do with a dried-tree :We can graft a dried-tree in a live tree. Once grafted, the dried-tree becomes a 'live' part of the tree.Moreover, we can also store the dried-tree in a box (a file) so that the bw-tree can be revitalized when the application re-starts ( or in a new application )
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- I believe we could review the whole terminology, converting the botanical terms in an proper graph-theory terminology ... this is not important here; purpose of this article is to discuss an extensions, determine its completeness and coherence, and discover its limitations.
- Lars H
- You wouldn't want the trees to be graph-theoretical trees, trust me. There are huge differences between what a computer scientist considers to be a tree and what a graph theorist considers to be a tree -- the computer scientists wants all sorts of bells and whistles in their constructs. and the bw-trees are clearly on the CS side. The botanical terminology seems entirely appropriate. On a completely different issue, you may want to think about whether it could be useful for a no-Tk interpreter to manipulate dried-trees.
That's the leading metaphor, now let's develope the idea ...
- We need a way to create copies of a (part of a ) bw-tree.
- These copies should be persistent, that is, they should survive after the application quits.
- A dried-tree is a compact linear notation for storing the structure and contents of a BWidget's tree (bw-tree).
- dried-tree can be used for restoring the original bw-tree,
- create a dried-tree from a (sub-)bw-tree
- graft the dried-tree under a node of a bw-tree (the original bw-tree or a different bw-tree)
- store the dried-tree in a file
- get a dried-tree from a file ( and then graft in a bw-tree)
Before looking at the core tcl-code for these new operations, I think it is important to look at some use cases:
- Let's start creating a (classic) bw-tree ...
# # this is our basic sample tree # package require BWidget pack [Tree .tree] .tree insert end root a -text Aaa .tree insert end root b -text Bbb .tree insert end root c -text Ccc .tree insert end a a1 -text Aa1 .tree insert end a a2 -text Aa2 .tree insert end c c1 -text Cc1 .tree insert end c c2 -text Cc2 # some decorations ... set font1 {Courier 10 bold} set font2 {Times 10 italic} set font3 {Helvetica 10 bold} .tree itemconfigure a -font $font1 -fill blue .tree itemconfigure a1 -font $font1 -fill blue .tree itemconfigure a2 -font $font1 -fill blue .tree itemconfigure b -font $font2 -fill gray .tree itemconfigure c -font $font3 -fill red .tree itemconfigure c1 -font $font3 -fill red .tree itemconfigure c2 -font $font3 -fill red.
- Get a clone
# clone the 'c' subtree set myDriedTree [BWidget::Tree::clone .tree c]
- Graft it under the "a" node (at position 1)
BWidget::Tree::graft $myDriedTree .tree "a" 1.
- Graft it in a new tree (under the root node)
toplevel .new ; pack [Tree .new.tree] BWidget::Tree::graft $myDriedTree .new.tree root end.
- Save it in a persistent store (a file)
BWidget::Tree::store $myDriedTree driedA.dat
- Retrieve a dried-tree from a file
set myDriedTree [BWidget::Tree::load driedA.dat] # .. then you can start grafting in a bw-tree ....
- The core tcl-code
## bwtree.tcl ## ## Copyright (c) 2005 <Irrational Numbers> : <[email protected]> ## ## This program is free software; you can redistibute it and/or modify ## it under the terms of the GNU General Public License as published by ## the Free Software Foundation. ## package require BWidget namespace eval BWidget::Tree { ### unnecessary code ### namespace export every cancel # constant. # This is a special nodeID representing the 'root' of the dried-tree. # Since "root" is a reserved ID for a bw-tree, and it is never copied, # we can use it in a dried-tree without fear of overlapping. variable pseudoRoot root proc _GetNodeOptions { tree node } { set res {} foreach c [$tree itemconfigure $node] { set option [lindex $c 0] set value [lindex $c 4] lappend res $option $value } return $res } # return value: a 'dried-tree' # i.e. a string containing a tcl-command # for rebuilding $node and all its descendants proc clone {tree nodeID} { variable pseudoRoot if { $nodeID == "root" } { set L "" foreach n [$tree nodes root] { append L [_clone $tree $n \$tgtIdx $pseudoRoot] append L {if { $tgtIdx != "end" } {incr tgtIdx}} \n } } else { set L [_clone $tree $nodeID \$tgtIdx $pseudoRoot] } return $L } proc _clone { tree nodeID idxString parent } { set options [_GetNodeOptions $tree $nodeID] set cmd [ format {set map(%s) [$tgtTree insert %s $map(%s) #auto %s ]} \ $nodeID $idxString $parent $options] append cmd \n foreach child [$tree nodes $nodeID] { append cmd [_clone $tree $child end $nodeID] } return $cmd } proc graft { driedTree tgtTree parent tgtIdx } { variable pseudoRoot set map($pseudoRoot) $parent # NOTE: $tgtTree, $tgtIdx are used by driedTree eval $driedTree } proc store { driedTree fileName } { set f [open $fileName w] puts $f "$driedTree" close $f } proc load { fileName } { set f [open $fileName r] set driedTree [read $f] close $f return $driedTree } } package provide BWidget::Tree 0.0
LIMITATIONSThis package (BWidget::Tree rev. 0.0) does not work if the cloned nodes contain some kind of reference to external objects.In particular, nodes having the "-image" and "-window" options set will introduce some usage limitations...
- -window
- since two nodes with the -window option cannot share the same object, it is not possible to 'duplicate' such nodes. You should take care of duplicating the referred widgets ... difficult ...
- -image
- the limitation is minor since an image can be shared by many nodes, but, before 'recreating' a tree in a new application, you should ensure that the referenced images have been already loaded.
ABU 21 Jun 2005 - Removed (commented) unnecessary code from the attached package.
Schnexel Wrrr, the BWidget tree is so stupid! Already the graphics says it all: Look at the Screenshots above: The children nodes´ lines branch before the parent node, so parent node and child node graphically have the same parent node (the +/- box). Is there any Tcl/Tk tree that one can take serious?
ABU I like BWidget Tree.
- The first reason is because it's pure-tcl code; it runs on ANY platform.
- The second reason is that it is quite complete, and it has a well founded drag&drop support.
- Third, altough its basic graphical look is notexciting, it is deeply customizable via 'configure'
[chin] - 2009-09-10 05:59:32The Id of the node is not maintained, if the tree is saved and loaded.ABU The Id of the new nodes is automatic; think it as a serial number. This is necessary to avoid duplicated IDs.