Hello Monks,

    The Geometry Manager docs (say, for example that of: pack) state the following
   -in => *$master*
             insert the slave(s) at the end of the packing 
             order for the master window.

[download]
This means,
  1. packs $widget inside of $master rather than the parent of $widget, which is the default. (Chapter 2: Mastering Perl/Tk -- Oreilly Press).

  2. Technically, any widget can be a parent of another widget, but life is easier when widgets are children of a Frame, or else we have to use the -in option with pack. (Chapter 11: Frames, MainWindow...)
    I'm interested to understand the usefulness of this option with respect to Tk::NoteBook. In Tk::NoteBook at a time there is only one active page. i.e. only one page is in a raised state. Therefore, if each page is to have same set of widgets displayed inside it, then instead of creating the widgets for each page in the Tk::NoteBook it is simply enough to create the widgets only once and then re-use the same widgets for all the other pages, after all only one page gets displayed at a time.

Here's a small program that attempts at this BUT FAILS. 
use strict;
use Tk;
use Tk::NoteBook;

my $mw = MainWindow->new;
$mw->geometry('100x200');
my $nb = $mw->NoteBook()->pack(-fill => 'both', 
                               -expand => 1);
                                
my $page_tab_01=$nb->add ("TAB-1", 
                          -label=>'TAB-1', 
                          -raisecmd=>\&callback_01);

my $page_tab_02=$nb->add ("TAB-2", 
                          -label=>'TAB-2', 
                          -raisecmd=>\&callback_02);

my $t_button = $page_tab_01->Button(-text=>'OK', 
                                   -command=>sub{exit});

MainLoop;

sub callback_01 {
    $t_button->packForget;
    $t_button->pack(-in=>$page_tab_01);
}

sub callback_02 {
    $t_button->packForget;
    $t_button->pack(-in=>$page_tab_02);  #<---ERROR HERE
}

[download]

    I get the following error
error:can't pack .notebook.tAB_1.button inside .notebook.tAB_2

[download]

    Please let me know as to what mistake I'm doing in the above prgram and is there any other method besides this to accomplish the re-use of widgets in different page-tabs.

Thank you very much

In reply to Usefulness of -in option in Geometry Management (Perl/Tk) by Anonymous Monk

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