call external functions in GTK+ gui - c

Question

Am having a main.c which is linked with some headers and other c files.After completing the program its a terminal based program which works with user input using switch.Its associated with a hardware board when i gives "o" it opens and "c" it closes.
I got a sample GTK+ gui code written in c with open cloase and quit buttons.How would i link my open and close functions with the open and cloase buttons in gui.
This is the GTK Code am Having
#include <gtk/gtk.h>
static void
print_hello (GtkWidget *widget,
gpointer data)
{
g_print ("Hello World\n");
}
int
main (int argc,
char *argv[])
{
GtkWidget *window;
GtkWidget *grid;
GtkWidget *button;
/* 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, and set its title */
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_window_set_title (GTK_WINDOW (window), "CANMate");
g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
gtk_container_set_border_width (GTK_CONTAINER (window), 50);
/* Here we construct the container that is going pack our buttons */
grid = gtk_grid_new ();
/* Pack the container in the window */
gtk_container_add (GTK_CONTAINER (window), grid);
button = gtk_button_new_with_label ("Open");
g_signal_connect (button, "clicked", G_CALLBACK (print_hello), NULL);
/* Place the first button in the grid cell (0, 0), and make it fill
* just 1 cell horizontally and vertically (ie no spanning)
*/
gtk_grid_attach (GTK_GRID (grid), button, 0, 0, 1, 1);
button = gtk_button_new_with_label ("Close");
g_signal_connect (button, "clicked", G_CALLBACK (print_hello), NULL);
/* Place the second button in the grid cell (1, 0), and make it fill
* just 1 cell horizontally and vertically (ie no spanning)
*/
gtk_grid_attach (GTK_GRID (grid), button, 1, 0, 1, 1);
button = gtk_button_new_with_label ("Quit");
g_signal_connect (button, "clicked", G_CALLBACK (gtk_main_quit), NULL);
/* Place the Quit button in the grid cell (0, 1), and make it
* span 2 columns.
*/
gtk_grid_attach (GTK_GRID (grid), button, 0, 1, 2, 1);
/* Now that we are done packing our widgets, we show them all
* in one go, by calling gtk_widget_show_all() on the window.
* This call recursively calls gtk_widget_show() on all widgets
* that are contained in the window, directly or indirectly.
*/
gtk_widget_show_all (window);
/* All GTK applications must have a gtk_main(). Control ends here
* and waits for an event to occur (like a key press or a mouse event),
* until gtk_main_quit() is called.
*/
gtk_main ();
return 0;
}

Answer 1

In the line
g_signal_connect (button, "clicked", G_CALLBACK (print_hello), NULL);
you are "connecting" a "signal handler": specifying that when button is clicked (that is, it emits the "clicked" signal), the function print_hello() should be called.
Just replace print_hello() with your open or close function, in the appropriate call for the open or close button.
EDIT: Passing parameters to the function
The signal handler is expected to have a prototype of the form:
void signal_handler (GtkButton *button, void *user_data)
The button parameter gets the button that was clicked, and user_data gets whatever you specified as the last parameter of g_signal_connect() -- in this case, NULL.
If you want to pass parameters to your open or close function, you will have to write an adapter function, such as the following:
void
on_open_click (GtkButton *open_button, void *user_data)
{
if (my_open_function (my_parameter_1, my_parameter_2) == UH_OH_ERROR) {
fprintf(stderr, "Something went wrong.\n");
}
And then connect it with g_signal_connect() instead of print_hello:
g_signal_connect (button, "clicked", G_CALLBACK (on_open_click), NULL);
In this case, my_parameter_1 and my_parameter_2 can be literal values, or global variables. You can also connect the signal in such a way that you can get values for these parameters through the user_data parameter in your signal handler. It's hard to say whether you need to do that, without knowing more about your open and close functions.