GTK+ Forums

xaos5 · Familiar Face Joined: 05 Nov 2006 Posts: 19

I'm new to gtk and currently learning. I've come across a problem I can't seem to understand. my program has two labels, two text entries, and one button. When the button is pushed I want it to grab the values in the two text boxes and store them in a structure. I have one function for creating my gui and another for doing what I will with the two text entries.

Code: (Plaintext)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41

/* create our main window */
void create_main_window(void);

/* callback to display a window with label displaying results calculated */
void calc_and_show_window(GtkWidget *widget, gpointer data);

struct car_data {
gfloat horsepower;
gfloat time;
gfloat weight;
};

...
...
...

void create_main_window(void)
{
...
...
...
/* calculate button */
button = gtk_button_new_with_mnemonic("_Calculate");
g_signal_connect(G_OBJECT(button), "clicked",
G_CALLBACK(calc_and_show_window), (gpointer)entry_weight); /* two arguments here maybe? */
g_signal_connect(G_OBJECT(button), "clicked",
G_CALLBACK(calc_and_show_window), (gpointer)entry_horsepower);
...
...
...
}

/* this is the function I haven't completed yet because I don't understand how to do it */
void calc_and_show_window(GtkWidget *widget, gpointer callback_data)
{
const gchar * horsepower =
gtk_entry_get_text(GTK_ENTRY(callback_data));
g_print("%s INCOMPLETE, FINISH ME!\n", horsepower);
}

I can post all my code if this isn't clear enough. Thanks in advance.

openldev · Posted: Sun Nov 05, 2006 5:17 pm Post subject:

You can't send multiple objects with g_signal_connect(). Instead, you want to do the following:

Code: (Plaintext)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28

typedef struct
{
GtkWidget *entry_weight, *entry_horsepower;
} Entries;

void create_main_window ();
void calc_and_show_window (GtkWidget*, Entries*);

struct car_data {
gfloat horsepower;
gfloat time;
gfloat weight;
};

void create_main_window(void)
{
Entries *w = g_slice_new (Entries);

button = gtk_button_new_with_mnemonic("_Calculate");
g_signal_connect(G_OBJECT(button), "clicked",
G_CALLBACK(calc_and_show_window), (gpointer) w);
}

void calc_and_show_window(GtkWidget *widget, Entries *w)
{
/* now you can use both entries here! */
}

You can cast the object type in your callback function automatically ...

xaos5 · Familiar Face Joined: 05 Nov 2006 Posts: 19

Thank you! Could you do me a favor and explain or direct me to site on g_slice_new()? Google has failed me. Now to go look up typedef in more detail (first language is c++ and been coding for about 6 months now).

openldev · Posted: Mon Nov 06, 2006 12:18 am Post subject:

Ok, well, if you go to the GLib API documentation, there's a section called Memory Slices that you should go over. Also, I have a book on GTK+ development coming in March 2007 that is available for preorder (http://book.andrewkrause.net), which covers memory allocation in detail. Here's an excerpt about g_slice_new():

xaos5 · Familiar Face Joined: 05 Nov 2006 Posts: 19

cool, how much does your book go in terms of introducing GTK+? I would like a book that shows the basics and at the same time explains itself, I usually end up finding one or the other.

openldev · Posted: Mon Nov 06, 2006 3:16 am Post subject:

It starts with the basics and then gets pretty heavy into things. You'll get a thorough coverage of GTK+, GLib, GObject and some Pango, GdkPixbuf and GDK. You'll learn how to make your own objects and there are examples for using almost every existing widget in GTK+.