Learning Perl/Tk

14.6. The bindtags Method

To find out the tags associated with a widget, use the bindtags method; for example:

print join(' ', $button->bindtags());
# prints this: Tk::Button .button . all
print join(' ', $mw->bindtags());
# prints this: MainWindow . all

This tells us the order in which the widget will respond to binding callbacks. The first response is always to the class that the widget belongs to; Tk::Button in the first example and MainWindow in the second.

The information returned from bindtags isn't nearly as interesting as what you can do with arguments sent to it. To remove all specific bindings from a widget except those that apply to 'all':

$button->bindtags(['all']);

Now the button will not respond to being pressed, mouse movements, or the default bindings associated with the widget. As demonstrated in the Perl/Tk web page for bindtags, you can reverse the order in which the widget responds to events like this:

$b->bindtags(['all',$b->toplevel,ref($b),$b]);

We already know that 'all' means any bindings associated with the special 'all' bindtag. Using $b->toplevel returns the window $b lives in: MainWindow=HASH(0x9798d8). Using ref($b) gives the package $b belongs to: Tk::Button. Finally, $bmeans the specific instance of $b: Tk::Button=HASH(0x99c0cc).

HASH(0x99c0cc) is a what we see when we print the value out. The hex number in parentheses is just the physical memory location of that widget. HASH means that it is stored in a hash structure.