efficient drawing of rectangles

["Cornelius Weig" <bitte keine werbung einwerfen googlemail com>]

I am writing a program, that involves drawing of an 2dim array of up to
300x300 squares. I use a pixmap to do offscreen drawing, afterwards the
pixmap is flushed to a GtkDrawingArea. For drawing to the pixmap I use
gdk_draw_rectangle, but the performance of this approach is somewhat
disappointing. It takes up to half a second for a whole drawing step which
is far less than what I would expect.
Is there a better way to do this in gtk? Does cairo perform better under
these circumstances?

Thanks