gdk_draw_layout on windows very slow

[Hubert Sokołowski <h sokolowski wsisiz edu pl>]

Hi!

I ported my application to windows using Dev-Cpp and gtk-2.0. I
figured out that it runs much slower on windows than on linux. I didn't
know why, the app only draws DrawingArea to white, than draws few
points, draw lines connecting this points and finally it draws numbers
over this lines using PangoLayout and gdk_draw_layout 
I use this function:

void draw_text (GdkPixmap *pixmap, GdkGC *gc, const gchar *str, gint x,
                gint y, PangoLayout *layout)
{
  pango_layout_set_markup (layout, str, -1);
  gdk_draw_layout (pixmap, gc, x, y, layout);
}

it draws on the pixmap then the pixmap is copied to the window.

I figured out that when I disable drawing the text it draws as fast as
on linux. why gdk_draw_layout takes so much CPU time on windows?

thanks in advance
hs