peterbe has asked for the wisdom of the Perl Monks concerning the following question:

I have a simple Tk::Tree object which displays a hierarchical listing of scripts and the modules 'use'd. By default Tk::Tree displays with the tree fully expanded; I want it to display with every node collapsed - so that the user can choose which nodes to traverse. Any ideas? Thanks, Peter (my first Perl Monks question!)

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Re: Tk::Tree - changing default behavior
by {NULE} (Hermit) on Nov 28, 2001 at 20:32 UTC
    Hi peterbe,

    Your best source of information on this is going to be the perldoc pages for Tk::Tree. Here is an example of how I create the browse trees collapsed.

    First start by creating your Tree (in this case I want it in a "Scrolled" widget): 

    $list = $browser->Scrolled(
    'Tree',
    '-relief' => 'sunken',
    '-border' => '2',
    '-width' => '80',
    '-height' => '30',
    '-scrollbars' => 'osoe',
    '-command' => \&edit
)->pack(
    '-side' => 'left',
    '-fill' => 'both',
    '-expand' => '1'
);

    [download]
    With your Tree widget created there are now three basic types of leaves on it - Primary ones that are parents only, Secondary that are parents and are also childern, and Tertiary that are children but are not parents. You can have multiple levels of the secondary ones.

    To create your primary leaves so that they are visible, but have all their children collapsed below them do this: 

    $list->add("rec$i", '-text' => "($i) $displayLine");
$list->setmode("rec$i", 'open');
$list->close("rec$i");

    [download]
    This creates the leaf, sets it to be "open-able" and then collapses the child leaves underneath. The secondary are created like this: 
    $list->add("rec$i.$j", '-text' => "$segments[$j]");
$list->setmode("rec$i.$j", 'open');
$list->close("rec$i.$j");
$list->hide('entry', "rec$i.$j");

    [download]
    This is close to what we do for the primary - except because its parent is closed we then hide the leaf. The tertiary are as follows: 
    $list->add("rec$i.$j.$k", '-text' => "$fields[$k]");
$list->hide('entry', "rec$i.$j.$k");

    [download]
    This just creates the leaf and hides it - it has no children of its own, so we are done.

    To see a working example of this you can take a look at my HL7 Browser which uses Tree for a living. This example was taken out of that code and cleaned up a bit for clarity. Figuring this out was a big pain for me, so I hope this helps you. :)

    Good luck,
    {NULE}
    --
    http://www.nule.org

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      {NULE} - Thanks for your detailed explanation. It works and I doubt if I could easily have figured this out from the perl/tk docs. My mistake was in thinking that Tk could simply collapse all nodes automatically. Instead, I needed to do some pre-processing in order to figure out the type of node I was dealing with. Many thanks again, Peter
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