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<TITLE> Creating Collapsible Tree Structures with TixTree<A NAME=42> </A></TITLE>
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<A NAME=Contents> </A><H2><A NAME=SECTION00062000000000000000> Creating Collapsible Tree Structures with TixTree<A NAME=42> </A></A></H2>
<P>
The TixTree widget is based on the TixScrolledHList widget; you can
use it to create a collapsible hierarchical structure so that the
user can conveniently navigate through a large number of list
entries. As shown in figure 4-7, the TixTree puts
the little ``<tt>+</tt>'' and ``<tt>-</tt>'' icons next to the branches of
an HList entry that has descendants. These two icons are knows as
the open and close icons, respectively. When the user presses the
open icon next to an entry, its immediate children of an entry will
be displayed. Conversely, when the user presses the close icon, the
entry's children will become hidden.
<P>
Program 4-6 shows how to create a collapsible tree. We
first create a TixTree widget. Then we add the entries in your
hierarchical structure into its <tt>hlist</tt> subwidget using the add
method of this subwidget. When we are finished with adding the entries,
we just call the <tt>autosetmode</tt> method of the TixTree widget, which
will automatically adds the open and close icons next to the entries who
have children.
<P>
<P><blockquote> <P><tt> set folder [tix getimage folder]<BR>
tixTree .tree -command Command -options {<BR>
hlist.separator /<BR>
hlist.itemType imagetext<BR>
hlist.drawBranch true<BR>
hlist.indent 18<BR>
}<BR>
pack .tree -expand yes -fill both<BR>
set hlist [.tree subwidget hlist]<BR>
<BR>
foreach directory {/ /usr /usr/bin /usr/local /etc /etc/rc.d} {<BR>
$hlist add $directory -image $folder -text $directory<BR>
}<BR>
.tree autosetmode<BR>
<BR>
proc Command {entry} {<BR>
puts "you have selected $entry"<BR>
}</tt>
<P></blockquote>
<P><CENTER>(Figure 4-6) Creating a Collapsible Hierarchy<A NAME=46> </A>
</CENTER>
<P>
<blockquote> <P>
<P><CENTER><IMG SRC="../gif/tix/hlist/hlist_ex3.gif">
</CENTER>
</blockquote>
<P>
Note that in program 4-6 we use the <tt>-command</tt> option of the TixTree
widget, not the <tt>-command</tt> option of its <tt>hlist</tt> subwidget. This
is because the TixTree actually used the <tt>-command</tt> option of its
<tt>hlist</tt> subwidget to process some low-level events. In general, if
both a mega-widget and its subwidget have the options of the same name,
you would always use the option that belongs to the mega-widget.
<P>
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