// gcc -Wall -g tray.c -o tray `pkg-config gtk+-2.0 --cflags --libs`
#include <stdio.h>
#include <stdlib.h>
#include <gtk/gtk.h>
#include <gdk/gdkx.h>

typedef struct tray_struct * trayicon;

void create_tray_and_dock (trayicon tray);

#define SYSTEM_TRAY_REQUEST_DOCK 0

struct tray_struct {
    Window manager_window;
    GdkWindow *manager_window_gdk;
    gint screen_height;
    GdkWindow *root_gdk;
    GdkWindow *plug_gdk;
    Window plug_xlib;
    GdkPixbuf *icon_pixbuf;
    Atom system_tray_opcode_atom;
    Atom manager_atom;
};

Window get_manager_window (void)
{
    static gboolean first_call=TRUE;
    static Atom selection_atom;
    Window manager_window=None;
    if (first_call) {
        gchar *tmp=g_strdup_printf ("_NET_SYSTEM_TRAY_S%i",
            XScreenNumberOfScreen(XDefaultScreenOfDisplay(GDK_DISPLAY())));
        selection_atom = XInternAtom(GDK_DISPLAY(), tmp, False);
        g_free (tmp);
        first_call=FALSE;
    }
    gdk_error_trap_push();
    XGrabServer (GDK_DISPLAY());
    manager_window = XGetSelectionOwner (GDK_DISPLAY(), selection_atom);
    XUngrabServer (GDK_DISPLAY());
    XFlush (GDK_DISPLAY());
    if (gdk_error_trap_pop())
        return None;
    printf ("get manager window: %d\n", manager_window);
    return manager_window;
}

void dock_window(trayicon tray)
{
    XClientMessageEvent ev;
    ev.type = ClientMessage;
    ev.window =tray->manager_window;
    ev.message_type =tray->system_tray_opcode_atom;
    ev.format = 32;
    ev.data.l[0] = CurrentTime;
    ev.data.l[1] = SYSTEM_TRAY_REQUEST_DOCK;
    ev.data.l[2] = tray->plug_xlib;
    ev.data.l[3] =0;
    ev.data.l[4] = 0;
    gdk_error_trap_push ();
    XSendEvent (GDK_DISPLAY(), tray->manager_window, False, 
        NoEventMask, 
        (XEvent *)&ev);
    XSync (GDK_DISPLAY(), False);
    gdk_error_trap_pop ();
}

void reparent_notify  (trayicon tray)
{
    XSetWindowBackgroundPixmap(GDK_DISPLAY(), tray->plug_xlib, 
        ParentRelative);
    XClearWindow (GDK_DISPLAY(), tray->plug_xlib);
    XFlush (GDK_DISPLAY());
}

void expose (trayicon tray)
{
    GdkGC *gc =gdk_gc_new (tray->plug_gdk);
    XClearWindow (GDK_DISPLAY(), tray->plug_xlib);
    XFlush (GDK_DISPLAY());
    gdk_draw_pixbuf (tray->plug_gdk, gc, tray->icon_pixbuf,
        0, 0, 0, 0, 24, 24, GDK_RGB_DITHER_NONE, 0, 0);
}

static GdkFilterReturn filter (GdkXEvent *xevent,
    GdkEvent *event, gpointer user_data)
{
    XEvent *xev = (XEvent *)xevent;
    trayicon tray = (trayicon) user_data;
    if (xev->xany.type == ReparentNotify) {
        printf ("reparen notify\n");
        reparent_notify(tray);
    }
    if (xev->xany.type == Expose) {
        printf ("expose notify\n");
        expose(tray);
    }

    return GDK_FILTER_CONTINUE;
}

void create_tray_and_dock (trayicon tray)
{
    if (tray->manager_window==None)
        tray->manager_window=get_manager_window();
    if (tray->manager_window==None)
        return;
    tray->manager_window_gdk=NULL;
    tray->manager_window_gdk=gdk_window_foreign_new(tray->manager_window);
    tray->plug_xlib= XCreateSimpleWindow(GDK_DISPLAY(), 
        GDK_ROOT_WINDOW(), 0,
        0, 24, 24, 0, 0, 0);
    XSelectInput(GDK_DISPLAY(), tray->plug_xlib, StructureNotifyMask | 
        ExposureMask);
    tray->plug_gdk=gdk_window_foreign_new (tray->plug_xlib);
    gdk_window_add_filter (tray->plug_gdk, filter, (gpointer) tray);
    dock_window (tray);
}

void trayicon_show (trayicon tray)
{
    g_assert (tray != NULL);
    tray->screen_height=gdk_screen_get_height (gdk_screen_get_default());
    tray->root_gdk =gdk_screen_get_root_window 
        (gdk_screen_get_default());
    tray->manager_window = get_manager_window ();
    tray->manager_window_gdk =NULL;
    create_tray_and_dock(tray);
}

trayicon trayicon_new(GdkPixbuf *default_icon)
{
    g_assert (default_icon != NULL);
    trayicon tray;
    printf ("trayicon_new\n");
    tray =(trayicon)g_malloc(sizeof(struct tray_struct));
    tray->manager_atom = XInternAtom (GDK_DISPLAY(), "MANAGER", False);
    tray->system_tray_opcode_atom = XInternAtom (GDK_DISPLAY(),
        "_NET_SYSTEM_TRAY_OPCODE", False);
    tray->icon_pixbuf=g_object_ref (default_icon);
    return tray;
}


int main (int argc, char *argv[])
{
    gtk_init (&argc, &argv);
    trayicon tray;
    GdkPixbuf *pixbuf=gdk_pixbuf_new_from_file ("/home/bob/Download/gaim.png", 
        NULL);
    tray=trayicon_new(pixbuf);
    g_object_unref (pixbuf);
    create_tray_and_dock(tray);
    //dock_window(tray);
    trayicon_show (tray);
    expose(tray);
    gtk_main ();
    return 0;
}