Display response time seems too slow on simple functions - c

Question

I have written an application in C using GTK 2.0 for a touchscreen panel with an ARM processor running debian linux. It is a very basic application that presents a few buttons (event boxes) on screen that can be clicked. On one page, I have 4 fields to present a "list" that can be scrolled through by clicking an up arrow and a down arrow (also event boxes). My function (code below) for the scrolling is very basic...it just updates each field with the next item from the array. Everything works fine, but the problem I am seeing is that if you repeatedly click the scroll button a little too quickly, it jumps ahead a few list items too far. My guess as to what is happening is that, when clicking too fast, the counter advances faster than the screen can update, so that by the time you click again it is actually updating with the then too-high counter. I wouldn't be concerned if it only happened when clicking REALLY fast, but I think the slow response seems way out of line for such a simple function repeating at a reasonably quick rate.
I'm hoping maybe someone has some input on something I might be missing in regards to screen refreshes with GTK?
Thank you in advance for any thoughts or advice!
Here is my code for my "volume-up" function and "scroll-up" function, both having the same problem. There are corresponding "scroll-down" and "volume-down" functions with the same issue:
static void sr_vol_up_clicked (GtkWidget *fakewidget, GdkEvent *fakeevent, gpointer number)
{
g_timer_start(lock_timer);
gtk_image_set_from_file (GTK_IMAGE(sr_vol_up_button),"./images/Admin/navigation_up_arrow_DOWN.png");
if (sr_current_level < 100)
{
sr_current_level = sr_current_level + 1;
gtk_label_set_text (GTK_LABEL(sr_current_level_label), (g_strdup_printf("%i", sr_current_level)));
set_sr_volume(sr_current_level);
}
gtk_image_set_from_file (GTK_IMAGE(sr_vol_up_button),"./images/Admin/navigation_up_arrow_UP.png");
}
And the other:
static void scroll_show_up ()
{
g_timer_start(lock_timer);
if (show_scroll_count > 0)
{
if (show_one_displayed - 1 < 0)
{
show_one_displayed = (show_loop_list->len -1);
}
else
{
show_one_displayed = show_one_displayed - 1;
}
gtk_label_set_text (GTK_LABEL(upcoming_show_1_label), get_show_name((char *)g_ptr_array_index(show_loop_list, show_one_displayed)));
if (show_two_displayed - 1 < 0)
{
show_two_displayed = (show_loop_list->len -1);
}
else
{
show_two_displayed = show_two_displayed - 1;
}
gtk_label_set_text (GTK_LABEL(upcoming_show_2_label), get_show_name((char *)g_ptr_array_index(show_loop_list, show_two_displayed)));
if (show_three_displayed - 1 < 0)
{
show_three_displayed = (show_loop_list->len -1);
}
else
{
show_three_displayed = show_three_displayed - 1;
}
gtk_label_set_text (GTK_LABEL(upcoming_show_3_label), get_show_name((char *)g_ptr_array_index(show_loop_list, show_three_displayed)));
if (show_four_displayed - 1 < 0)
{
show_four_displayed = (show_loop_list->len -1);
}
else
{
show_four_displayed = show_four_displayed - 1;
}
gtk_label_set_text (GTK_LABEL(upcoming_show_4_label), get_show_name((char *)g_ptr_array_index(show_loop_list, show_four_displayed)));
show_scroll_count = show_scroll_count - 1;
}
}