[Glade-users] get/set GTK widget properties.

[Tristan Van Berkom]

On Thu, May 16, 2013 at 5:53 PM, dE <de.techno at gmail.com> wrote:
> Hello everyone!
>
> I'm using Glade to make the GUI (actually it's made), as a result I don't
> have much idea about the coding part (in C) neither there are any tutorials
> which focus on the coding part with Glade, most of them being Python based.
>
> How do you change/set the property of a widget? For e.g. a button label, or
> read buffer text in an input box?
>
> I've realized that every widget type has a dedicated structure assigned to
> it, for e.g. Gtkbutton, or GtkEntry, and each widget has properties, e.g. --
>
> https://developer.gnome.org/gtk3/3.2/GtkButton.html#GtkButton.properties
>
> But how do you get or change these properties? The structure of the widget
> does not have have these elements, as a result you can't GtkEntry.buffer.
>
> So how do you access these properties?
>
> I've noticed these functions --
>
> gtk_button_get_label
> gtk_button_set_use_stock
> gtk_button_set_image
> ...

That's right, you should use the API provided by a widget class to
set it's properties.

>
> Which may be used to modify the widget properties, but I get --
>
> "(a.out:23415): Gtk-CRITICAL **: gtk_entry_get_text: assertion `GTK_IS_ENTRY
> (entry)' failed"
>
> on
>
> gtk_entry_get_text(test);
>
> In function --
>
> void test_func(GtkEntry *test)

Then the pointer you gave to gtk_entry_get_text() does not actually
point to a GtkEntry object.

Perhaps it's NULL, or a wild pointer that's only casted as a GtkEntry *.

> Where glade is set to run this function and pass "entry2" (in "user data" of
> the signals tab) on event GtkButton > released.

Ah, then you have a bad callback signature see this documentation
for the signature of a callback for the GtkButton::released signal:

https://developer.gnome.org/gtk3/unstable/GtkButton.html#GtkButton-released

Notice that you are actually passing the button which emitted the "released"
signal as an entry to gtk_entry_set_text().

Every signal has a different signature, you need to pass the correct type
of callback when connecting to any signal.

If Glade is installed on a system with DevHelp also installed, you should
be able to get the signal documentation directly by clicking the devhelp
icon for a given signal in the signal editor.

Cheers,
    -Tristan

>
> If this's how you get/set properties, then of what use are the properties as
> listed in --
>
> https://developer.gnome.org/gtk3/3.2/GtkButton.html#GtkButton.properties
>

Those are GObject properties, they can be set for any object with
g_object_set()/g_object_get() or passed to g_object_new(), but
it's recommend to use the actual API to modify objects rather
than g_object_set/get (the g_object_set()/get() apis are rather
for more generic access, i.e. GtkBuilder uses them when
building an interface defined with Glade).

> Thankyou for the help, I need this to be fixed quick.
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