Simple GTK 3 example of how to use GtkScale (which inherits from GtkRange) in C.

scale.c

/** scale.c
 *
 * GTK3 example of how to use GtkScale (which inherits from GtkRange).
 *
 * COMPILE
 * gcc -Wall -o scale scale.c `pkg-config --libs --cflags gtk+-3.0`
 *
 * EXAMPLE
 * ./scale
 *
 */

#include <gtk/gtk.h>

void value_changed(GtkRange*, gpointer);

int main(int argc, char** argv) {
    // Initialize GTK
    gtk_init(&argc, &argv);

    // Create the window
    GtkWidget* window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 250, 50);
    gtk_window_set_resizable (GTK_WINDOW(window), FALSE);
    gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);

    // Create the root widget, which contains all the other widgets
    GtkWidget* root = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 20);

    // Create the scale widget, a type of range widget.
    GtkWidget* scale =
            gtk_scale_new_with_range(GTK_ORIENTATION_HORIZONTAL, 0, 100, 1);
    gtk_scale_set_draw_value(GTK_SCALE(scale), FALSE);
    gtk_widget_set_size_request(scale, 150, -1);

    // Create label to show current value 
    GtkWidget* label = gtk_label_new("0");

    // Pack the scale widget and label into the root widget
    gtk_box_pack_start(GTK_BOX(root), scale, FALSE, FALSE, 0);
    gtk_box_pack_start(GTK_BOX(root), label, FALSE, FALSE, 20);

    // Add the root widget to the window
    gtk_container_add(GTK_CONTAINER(window), root);

    // Connect signal handlers
    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
    g_signal_connect(scale, "value-changed", G_CALLBACK(value_changed), label);            

    // Show the window
    gtk_widget_show_all(window);

    // Start the GTK main loop
    gtk_main();

    return EXIT_SUCCESS;
}

static gchar label_text[4] = {0};

void value_changed(GtkRange* range, gpointer window) {
    guint8 value = gtk_range_get_value(range);
    value = value < 0 ? 0 : value > 100 ? 100 : value;
    snprintf(label_text, 4, "%d", value);
    gtk_label_set_text(GTK_LABEL(window), label_text);
}