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var guckets_icon: pGdkPixbuf;
var mainWindow: pGtkWIdget;
....
mainWindow := gtk_window_new(GTK_WINDOW_TOPLEVEL);
...
guckets_icon := gdk_pixbuf_new_from_file(pgChar(config.datadir + 'images/guckets.png'), nil);
...
gtk_window_set_icon(GTK_WINDOW(mainWindow), guckets_icon);