如何将符号GtkIconSize转换为以像素为单位的整数？

gint gtk_icon_size_lookup(GtkIconSize size);

#include <gtk/gtk.h>

int main(int argc, char *argv[]) {
    gtk_init(&argc, &argv);

    GtkIconSize size = GTK_ICON_SIZE_LARGE;
    gint pixel_size = gtk_icon_size_lookup(size);

    if (pixel_size != -1) {
        g_print("GtkIconSize %d is equivalent to %d pixels.\n", size, pixel_size);
    } else {
        g_print("Invalid GtkIconSize value.\n");
    }

    return 0;
}