is there a way for instantly drawing

[Jiang XU <jiang xu echostar com>]

I use gdk_draw_line() and other drawing function to draw a
GtkDrawingArea.
Since I use multi threads( using gdk_thread_lock....), I wonder whether
there is a way to instantly drawing.
Which means, after calling gdk_draw_line() (and other drawing
functions), the screen immediately shows what you have drawed.
I tried to emit the signal "expose_event" for that GtkDrawingArea, but
it doesn't work.
I also tied to use "gtk_widget_draw", which is some sort of the same
ways, but also failed.

Is there such a way to do that?

If anybody knows, teach me please

Thanks