newbie GLOrtho2d question

Hi, i wanna use a 2D screen with
::gluOrtho2D(-10.0f, 10.0f, -10.0f, 10.0f);
Now, when I draw a line like this :

glVertex2f(-10, 0);
glVertex2f(10, 0);

initially the line is ok, but by rezising the screen, the line doesnt reach the right side of the client area … How does this system work ?

If you resize the window, you must also resize OpenGL’s viewport. You do that with glViewport. glViewport tells OpenGL to what parts of the window you want to draw to.