Learning Perl/Tk

Chapter 2. Geometry Management

To display widgets on the screen, they must be passed to a geometry manager. The geometry manager controls the position and size of the widgets in the display window. There are several geometry managers available with Perl/Tk: pack, place, and grid.

All three geometry managers are invoked as methods on the widget, but they all have their own methodologies and arguments to change where and how the widgets are put on the screen:

$widget1->pack(); $widget2->place(); $widget3->grid();

When you organize the widgets in your window, it is often necessary to separate groups of widgets to get a certain look and feel. For instance, when you use pack(), it is difficult to have widgets stacked both horizontally and vertically without grouping them in some fashion. We group widgets by using a frame widget inside a window or by using another window (a toplevel widget).

We create our first window by calling MainWindow. The MainWindow is a special form of a toplevel widget. For more detailed information on how to create/configure frames and toplevel widgets, see Chapter 12, and Chapter 13.

Because of the differences between the three geometry managers, it is difficult (not entirely impossible, but definitely not recommended) to use more than one geometry manager within the same area. In our $mw, I can display many types of widgets, but if I start using pack(), I should continue to use pack() on all of the widgets contained directly in $mw. I wouldn't want to switch ...