MainWindow

Section: User Contributed Perl Documentation (3)
Updated: 2021-01-27
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NAME

Tk::MainWindow - Root widget of a widget tree

SYNOPSIS

    use Tk;

    my $mw = MainWindow->new( ... options ... );

    my $this = $mw->ThisWidget -> pack ;
    my $that = $mw->ThatWidget;
    ...

    MainLoop;

DESCRIPTION

Perl/Tk applications (which have windows associated with them) create one or more MainWindows which act as the containers and parents of the other widgets.

Tk::MainWindow is a special kind of Toplevel widget. It is the root of a widget tree. Therefore "$mw->Parent" returns "undef".

The default title of a MainWindow is the basename of the script (actually the Class name used for options lookup, i.e. with basename with inital caps) or 'Ptk' as the fallback value. If more than one MainWindow is created or several instances of the script are running at the same time the string " #n" is appended where the number "n" is set to get a unique value.

Unlike the standard Tcl/Tk's wish, perl/Tk allows you to create several MainWindows. When the last MainWindow is destroyed the Tk eventloop exits (the eventloop is entered with the call of "MainLoop"). Various resources (bindings, fonts, images, colors) are maintained or cached for each MainWindow, so each MainWindow consumes more resources than a Toplevel. However multiple MainWindows can make sense when the user can destroy them independently.

METHODS

You can apply all methods that a Toplevel widget accepts.

The method $w->MainWindow applied to any widget will return the MainWindow to which the widget belongs (the MainWindow belongs to itself).

MISSING

Documentation is incomplete. Here are some missing items that should be explained in more detail:

•: The new mechanism for MainWindows is slightly different to other widgets.
•: There no explanation about what resources are bound to a MainWindow (e.g., ClassInit done per MainWindow)
•: Passing of command line options to override or augment arguments of the "new" method (see Tk::CmdLine).