title: how to get new coordinate for drawing point?
body: <p>I have an if clause in function <code>myMouse()</code>. in it's condition, if the coordinate of <code>x</code> and <code>y</code> was in the certain place, I want to draw a point in the <strong>new coordinate</strong> that <code>myMouse()</code> <strong>takes from user</strong>!
  I'm beginner in openGl. please help me how can I define a drawdot function that draws a point in new coordinates after checking condition. and this is part of my code:</p>
  
  <pre><code>void myMouse(int button, int state, int x, int y)
  {
      if(button==GLUT_LEFT_BUTTON &amp;&amp; state==GLUT_DOWN &amp;&amp; ((x&gt;=30 &amp;&amp; x&lt;=70) &amp;&amp; ((wh-y)&gt;=400 &amp;&amp; (wh-y)&lt;=440)))
          {status=1;
      drawdot(x,y);}
  </code></pre>