How to get XTest to work with xvfb

[ying lcs]

Hi,

I have a program which uses XTest to simulate a mouse click to my program.

It works if my program is running in a visible display.  But when I
setup xvfb and set my program to display there, the mouse click
simulation does not work.

Can you please tell me how to get XTest to work with xvfb?

Thank you.

    XTestFakeMotionEvent( xdisplay, gdk_x11_get_default_screen(),
			  x,
			  y,
			  0 );

    XTestFakeButtonEvent( xdisplay, 1, TRUE, 0 );
    XTestFakeButtonEvent( xdisplay, 1, FALSE, 0 );