Usefulness of -in option in Geometry Management (Perl/Tk)

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

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,

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

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

Comment on Usefulness of -in option in Geometry Management (Perl/Tk) Select or Download Code

Replies are listed 'Best First'.
Re: Usefulness of -in option in Geometry Management (Perl/Tk) by Loops (Curate) on Nov 24, 2014 at 09:06 UTC
Tk apparently has two separate hierarchies, parent/child and master/slave. And in my vague and limited understanding, the first controls stacking order and the second controls geometry (screen space). So taking a wild guess here, trying to repack a button with first tab parent into a second tab, changes the geometry but not the parent/child relationship -- meaning the stacking wouldn't work. Take that with a grain of salt, but if you change your button to be a child of the main window, your code works: `my $t_button = $mw->Button(-text=>'OK', -command=>sub{exit});` [download]	[reply] [d/l]
Re^2: Usefulness of -in option in Geometry Management (Perl/Tk) by Anonymous Monk on Nov 24, 2014 at 18:56 UTC
Hello Loops, Thanks a lot for your swift response and insight. I also read through another response from AM. Just to make sure I understand this correctly, A parent/child hierarchy is established at the creation phase of objects. For ex: `my $t_button = $mw->Button(-text=>'OK', -command=>sub{exit});` [download] This makes the object pointed to by `$t_button` a child of the object pointed to by `$mw`. A master/slave hierarchy is established by the geometry manager used(such as `grid, pack, form, place`). When displaying a widget, if the `-in` option is not at all used then the master/slave hierarchy is exactly the same as parent/child hierarchy. If this understanding of mine is correct, then I proceed to a portion of your next statement: ....trying to repack a button with first tab parent into a second tab, changes the geometry... This, I believe, you meant that the `pack` geometry manager attempts to pack first tab inside the second tab of the same `NoteBook.` This of-course is not permitted, after all every tab of any given `NoteBook` must NOT ONLY be a direct child BUT ALSO a direct slave under that `NoteBook` ...but not the parent/child relationship -- meaning the stacking wouldn't work. This I didn't understand, honestly. So please let me know. Moving on...Yes, after you said that making button a child of main window, I tried it and it works. But if I change the button to be a child of `NoteBook` i.e. `my $t_button = $nb->Button(-text=>'OK', -command=>sub{exit});` [download] Then not only does the button not show up, I don't get any error from the execution of `pack` statement inside the callbacks either when the callbacks are executed. What's going on ? Can you please tell me what's the problem here? Hey, Thank you for your patience in reading my query.	[reply] [d/l] [select]
Re^2: Usefulness of -in option in Geometry Management (Perl/Tk) by Anonymous Monk on Nov 27, 2014 at 03:48 UTC
Hello Loops, I just chanced to see some details on this. http://stackoverflow.com/questions/18106377/cant-pack-a-widget-inside-a-sibling-toplevel the first para of response from Donal Fellows and the last response dated Aug 7 '13 at 17:37 from Elchonon Edelson. http://stackoverflow.com/questions/21467113/is-there-a-limit-on-the-length-or-nesting-of-tcl-tk-widget-pathnames/21468948#21468948 the response dated Jan 30 at 22:39 from Donal Fellows. Those being the responses about pure Tcl/Tk I didn't quite understand what they said. Do you have any explanation/thoughts from your side ? Thank you	[reply]
Re: Usefulness of -in option in Geometry Management (Perl/Tk) by Anonymous Monk on Nov 24, 2014 at 10:26 UTC
I get the following error error:can't pack .notebook.tAB_1.button inside .notebook.tAB_2 Please let me know as to what mistake I'm doing Look at it this way :) its a path `error:can't pack .notebook.tAB_1.button inside .notebook.tAB_2` [download] its a path `.notebook.tAB_1.button .notebook.tAB_2` [download] its a parent child relationship `.grandpa.daddy.baby .grandpa.uncle` [download]	[reply] [d/l] [select]