What is a toplevel widget?

killocan · **Posted:** Thu Apr 03, 2008 9:23 pm

Hi! I'm seeking information on widgets destruction process. And I'm wondering what,
exactly, is a TOP-LEVEL widget, :) i have searched through a lot of sites and
documentations and they are a bit confuse about whats a top-level widget truly means.
For example, i found this statement:

1) If the widget "owns" any widgets other than its child
widgets, (for instance popup windows) it should
call gtk_widget_destroy () for them.

In another site (developers section at gnome site):

* In practice, this means that you only have to destroy toplevel widgets;
any widgets that are inside a container will be destroyed along with the container.

Ok at this point i figure out to myself that ANY gtk component child of GtkContainer
is itself a TOP-LEVEL widget, but in GtkWidget section (gtk_widget_destroy) i get:

...
* In most cases, only TOPLEVEL widgets (WINDOWS) require explicit destruction,
because when you destroy a toplevel its children will be destroyed as well.

So, i guess, I get it right. A TOP-LEVEL widget is, ANY, widget child of GtkContainer, and
this note (WINDOWS) in gtk_widget_destroy docs is just an example :)

NOTE: I looked at an pygtk site that states:
...
* If the widget is a toplevel (derived from gtk.Window ), it will be removed
from the list of toplevels...

This is very weird! :)

So, am i wrong about (TOPLEVEL == any GtkContainer) or not? :) Thanks!

openldev · **Posted:** Sun Apr 06, 2008 2:51 pm

Let's assume you have a window that contains a GtkHBox that contains other widgets. The window is the top-level widget since it has no parent widget. Top-level widgets have no parent widget. When you call gtk_widget_destroy() on a top-level, all of its children will also be destroyed, which means that you only need to call that function once for each top-level widget.

killocan · **Posted:** Sun Apr 06, 2008 6:49 pm

So, if i destroy only the HBox all components inside it will remain?

openldev · **Posted:** Sun Apr 06, 2008 8:32 pm

The other way around. If you destroy the HBox, it will also destroy all of its children. The ancestors (parent, etc) will be left.

killocan · **Posted:** Sun Apr 06, 2008 9:05 pm

So the HBox can be called "toplevel" widget if we forget about the window. I mean, when we delete a HBox it will (remove/destroy) itself from the parent, and then clean (remove/destroy) all it's child... unless some child has a reference count higher that 1. right? :)

openldev · **Posted:** Sun Apr 06, 2008 10:32 pm

Correct in terms of the destroying. However, while you could technically call the HBox a top-level, in GTK+ that term should only be used to refer to widgets that can be displayed on the screen without a parent.

killocan · **Posted:** Mon Apr 07, 2008 1:18 pm

Ok! I get it! Thank you so much!!!

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What is a toplevel widget?

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