Re: Accessing the window inside the widget

On Fri, Jan 27, 2012 at 10:33 PM, Manuel Ferrero <[email protected]> wrote:
> A simple program:
>
> ---SNIP---
> GtkWidget *my_window;
> GtkBuilder *builder_handler;
>
>
> builder_handler = gtk_builder_new();
> gtk_builder_add_from_file(builder_handler, GUI_XML_FILENAME, NULL);
>
> my_window = GTK_WIDGET(gtk_builder_get_object(builder_handler, "window"));
> ---PINS---
>
>
> Now my_window is a GtkWidget and its class hierarchy tree is the following:
>
> +GtkWidget
> |+GtkContainer
>  |+GtkBin
>  |+GtkWindow
>
> Almost every function to manipulate windows requires a GtkWindow pointer,
> i.e.:
> void gtk_window_set_resizable(GtkWindow *window, gboolean resizable);
>
> How do I get the GtkWindow pointer from the GtkWidget I get after the
> builder?

With the standard type casting macros:

GtkWidget *widget;
GtkWindow *window;

widget = gtk_builder_get_object (builder, "window");
window = GTK_WINDOW (widget);

gtk_window_do_something_from_the_window_api (window, argument);

Likewise, you can simply cast the pointer in the function argument like so:

gtk_window_do_something_from_the_window_api (GTK_WINDOW (widget), argument);

Usually we hold all widgets in a GtkWidget pointer regardless of the type, just
because chances are you will be accessing GtkWidget apis more regularly
than other apis.

If you are concerned with performance, and you will call multiple apis from
the GtkWindow api, then it's (slightly) worthwhile to create a GtkWindow pointer
and use that pointer instead.

This is because the standard type casting macros fire runtime assertions for
type mismatches (i.e. the macros include run-time type checking).

Cheers,
            -Tristan

>
> Thanks in advance.
> --
> Regards,
> Manuel Ferrero
> R&D department
>
> Reer SpA
> Tel.  +39 011 2482215
> Fax. +39 011 859867
>
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