這段code哪有問題嗎!!?

shien

#include <stdio.h>
#include <string.h>
#include <gdk/gdkx.h>
#include <gtk/gtk.h>
#include <sys/time.h>
#include <gdk/gdkkeysyms.h>
#include <utime.h>
#include <time.h>
#include <glib.h>
#include <unistd.h>

#define FONT        -*-helvetica-medium-*-*--36-*-*-*-*-*-iso8859-1"

int main(int argc,char *argv[])
{
        GdkWindowAttr attr;
        GdkGCValues value;
        GdkWindow *win;       
        GdkGC *gc;
        GdkFont *font;
        Display *dpy;
        int position_x =300;
        int x = 300;
        int total_width = 0;
       
        gdk_init(&argc,&argv);

    attr.wclass=GDK_INPUT_OUTPUT;
    attr.width  = 400;
    attr.height = 300;
    win = gdk_window_new(NULL, &attr, GDK_WA_X|GDK_WA_Y);
       
        value.line_width = 0;
        gc         = gdk_gc_new_with_values(win,&value,GDK_GC_FOREGROUND );

    gdk_window_show(win);
       
        font=gdk_font_ref(gdk_fontset_load(FONT));
        total_width = gdk_string_width( font,"tttttttttttttttttttt");

        while(1){
                gdk_window_clear(win);
                gdk_draw_string(win, font, gc, position_x, 150, "tttttttttttttttttttt");
                position_x = position_x -1;
                usleep(15000);

                if((position_x < -total_width) ){
                                total_width=gdk_string_width( font,"tttttttttttttttttttt");
                                position_x = x;
                }               
                gdk_flush();       
        }

        return 1;

}


不知道哪有問題 文字會閃動 >"<
試了好久 我想做跑馬燈~
請各位大大幫忙看看 Thanks