How to get the end of continuous value update for Gtk Spinbox? - event-handling

Question

I'm using Gtk2 to make a small tool, it works like this:
Several Scales and Spinboxes control parameters of an algorithm.
When parameter changes, the algorithm will execute, and the updated result is rendered as a picture, shown in UI.
As the algorithm's workload is heavy, I don't want it run frequently during frequent parameter change. Specifically, during Scales are dragged or Spinbox's arrows buttons are pressed. Instead, I want the algorithm to be run "after" users have determined the parameters.
Currently, I listened the button-release event of the Scales, so the algorithm will run only on Scale dragging is done. However, this not fit for the Spinboxes, as they have separate entry and button sub-area. If I listen to Spinbox's button-release, it would behave weirdly.
So what event (or events) should I listen to obtain the occation that a continuous value update is finished for a Spinbox?

Answer 1

Could I see the code you have? The button-release works great for me. However, depending on your algorithm, you may be getting 'feedback'. Are you sure the rest of the code is not updating your spinbutton in some way?

Answer 2

I'd use a deferred computation, independent from the device you use to modify the data. In this way you can also input the numbers with the keyboard or copy and paste their content and the program will still work as expected.
A way to do this in GTK+ is by leveraging the main loop and using a timeout GSource, e.g.:
#include <gtk/gtk.h>
typedef struct {
guint event;
GSourceFunc callback;
GtkWidget *spin_button;
} Algorithm;
static gboolean your_callback(Algorithm *algorithm)
{
g_print("Your heavy computations go here...\n");
/* ... */
algorithm->event = 0;
return FALSE;
}
static void postpone(Algorithm *algorithm)
{
if (algorithm->event > 0) {
g_source_remove(algorithm->event);
}
/* Default delay is 1 second (1000 milliseconds) */
algorithm->event = g_timeout_add(1000, algorithm->callback, algorithm);
}
int main(int argc, char **argv)
{
GtkWidget *window, *spin_button;
Algorithm algorithm;
gtk_init(&argc, &argv);
spin_button = gtk_spin_button_new_with_range(0, 100, 0.1);
g_signal_connect_swapped(spin_button, "value-changed",
G_CALLBACK(postpone), &algorithm);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_container_add(GTK_CONTAINER(window), spin_button);
algorithm.event = 0;
algorithm.callback = (GSourceFunc) your_callback;
algorithm.spin_button = spin_button;
gtk_widget_show_all(window);
gtk_main();
return 0;
}