Change a label in GTK+ 2 - Programmers Heaven

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Change a label in GTK+ 2

Hello, I am learning C and decided to have a look into programming GUI's with GTK+, so i have been going through the GKT+ 2 tutorial at I have created an appliction from the two button demo to tally up votes. I want the string at the bottom of the box to change to the percent of positive votes. I cannot get the label's text to change. Does anybody know how this is done? or if I am using the wrong widget? Thanks -Robert

Here is my code so far.
float y = 0;
float n = 0;
float t = 0;
float p = 0;
GtkWidget *label2;
char coolness[20];
/* Our new improved callback. The data passed to this function
* is printed to stdout. */
static void callback( GtkWidget *widget,
gpointer data )
if(y==1) g_print ("1 person thinks C is cool,");
else g_print ("%.0f people think C is cool,", y);
if(n==1) g_print (" and 1 person thinks C is uncool.
else g_print (" and %.0f people think C is uncool.
", n);
g_print ("%s

/* another callback */
static gboolean delete_event( GtkWidget *widget,
GdkEvent *event,
gpointer data )
gtk_main_quit ();
return FALSE;
static void updown( GtkWidget *widget,
gint data)
if(data) y++;
else n++;
t = y + n;
p = 100 * y / t ;
/*void gtk_label_set_text( GtkLabel *label,
const char *str );*/
static void updatelabel2(void)
void gtk_label_set_text( GtkLabel *label2,
const char *coolness );

int main( int argc,
char *argv[] )

/* GtkWidget is the storage type for widgets */
GtkWidget *window;
GtkWidget *button;
GtkWidget *box1;
GtkWidget *box0;
GtkWidget *label;

/* This is called in all GTK applications. Arguments are parsed
* from the command line and are returned to the application. */
gtk_init (&argc, &argv);

/* Create a new window */
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

/* This is a new call, which just sets the title of our
* new window to "Please Vote" */
gtk_window_set_title (GTK_WINDOW (window), "Please Vote");

/* Here we just set a handler for delete_event that immediately
* exits GTK. */
g_signal_connect (G_OBJECT (window), "delete_event",
G_CALLBACK (delete_event), NULL);

/* Sets the border width of the window. */
gtk_container_set_border_width (GTK_CONTAINER (window), 10);

/* We create a box to pack widgets into. This is described in detail
* in the "packing" section. The box is not really visible, it
* is just used as a tool to arrange widgets. */
box0 = gtk_vbox_new (FALSE, 0);
box1 = gtk_hbox_new (FALSE, 0);

/* Put the box into the main window. */
gtk_container_add (GTK_CONTAINER (window), box0);

/* Creates a new button with the label "Yes". */
button = gtk_button_new_with_label ("Yes!");

/* Now when the button is clicked, we call the "callback" function
* with a pointer to "button 1" as its argument */
g_signal_connect (G_OBJECT (button), "clicked",
G_CALLBACK (updown), (gpointer) 1) ;

g_signal_connect (G_OBJECT (button), "clicked",
G_CALLBACK (callback), (gpointer) "is");

g_signal_connect (G_OBJECT (button), "clicked",
G_CALLBACK (updatelabel2), NULL);

/* Instead of gtk_container_add, we pack this button into the invisible
* box, which has been packed into the window. */
gtk_box_pack_start (GTK_BOX(box1), button, TRUE, TRUE, 0);

/* Always remember this step, this tells GTK that our preparation for
* this button is complete, and it can now be displayed. */
gtk_widget_show (button);

/* Do these same steps again to create a second button */
button = gtk_button_new_with_label ("No!");

/* Call the same callback function with a different argument,
* passing a pointer to "button 2" instead. */
g_signal_connect (G_OBJECT (button), "clicked",
G_CALLBACK (updown), (gpointer) 0);

g_signal_connect (G_OBJECT (button), "clicked",
G_CALLBACK (callback), (gpointer) "isn't!");

g_signal_connect (G_OBJECT (button), "clicked",
G_CALLBACK (updatelabel2), NULL);

gtk_box_pack_start(GTK_BOX (box1), button, TRUE, TRUE, 0);

label = gtk_label_new ("Do you think C is cool?");

gtk_misc_set_alignment (GTK_MISC (label), 0.5, 0);

gtk_widget_show (label);

gtk_box_pack_start (GTK_BOX (box0), label, FALSE, FALSE, 0);

gtk_box_pack_start(GTK_BOX (box0), box1, TRUE, TRUE, 0);

label2 = gtk_label_new ("C is cool!");

gtk_misc_set_alignment (GTK_MISC (label2), 0.5, 0);

gtk_box_pack_start(GTK_BOX (box0), label2, TRUE, TRUE, 0);

/* The order in which we show the buttons is not really important, but I
* recommend showing the window last, so it all pops up at once. */
gtk_widget_show (label2);

gtk_widget_show (button);

gtk_widget_show (box1);

gtk_widget_show (box0);

gtk_widget_show (window);

/* Rest in gtk_main and wait for the fun to begin! */
gtk_main ();

return 0;

Thanks :)
PS - I am new to C as well.


  • phorgan1phorgan1 Posts: 1Member
    : static void updatelabel2(void)
    : {
    : void gtk_label_set_text( GtkLabel *label2,
    : const char *coolness );
    : }
    Here's the problem. You declared gtk_label_set_text instead of calling it. Change it to:
    static void updatedlabel2(void)

    There--problem fixed.

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