Fullscreen can't control menu

Hi all,

I’m writing a OpenGL program in C. I have created a fullscreen mode using the following code:

if (fullscreen)
Xpos = glutGet((GLenum)GLUT_WINDOW_X); /* Save parameters /
Ypos = glutGet((GLenum)GLUT_WINDOW_Y);
Xsize = glutGet((GLenum)GLUT_WINDOW_WIDTH);
Ysize = glutGet((GLenum)GLUT_WINDOW_HEIGHT);
glutFullScreen(); /
Go to full screen */

It works well when I press the F1 key. I also created a right-click mouse menu. But when I switched to the fullscreen mode, the first time it works. But then when I right-click the menu again, it doesn’t have any response, only remain in fullscreen. Is there any problem with my code?