title: Triangle is taking up whole window?
body: <p>I am trying to draw a triangle using GL_POLYGON but for some reason it is taking the whole window..</p>
  
  <pre><code>...
  typedef struct myTriangle {
     float tx;
     float ty;
  } myTriangle;
  
  std::vector&lt;myTriangle&gt; container;
  
  void display() {
     glClear(GL_COLOR_BUFFER_BIT);
  
     for(int i = 0; i &lt; (int)container.size(); ++i) {
        glBegin(GL_POLYGON);
        glColor3f(0.35, 0.0, 1.0);
        glVertex2f(container.at(i).tx, container.at(i).ty + 20);
        glVertex2f(container.at(i).tx - 20, container.at(i).ty - 20);
        glVertex2f(container.at(i).tx + 20, container.at(i).ty - 20);
        glEnd();
     }
  
     glutSwapBuffers();
  }
  
  ...
  
  int main(int argc, char** argv) {
     myTriangle t1;
     container.push_back(t1);
     container.back().tx = (float)0.;
     container.back().ty = (float)0.;
  
     glutInit(&amp;argc, argv);
     glutInitDisplayMode(GLUT_DOUBLE);
  
     // initializations
     glutInitWindowSize(400, 400);
     glutInitWindowPosition(100, 100);
     glutCreateWindow( "Transformer" );
     glClearColor(1.0, 1.0, 1.0, 1.0);
  
     // global variable initialization
     GW = GH = 200;
  
     // callback functions
     glutDisplayFunc(display);
     glutMouseFunc(mouse);
     glutMotionFunc(mouseMove);
     glutKeyboardFunc(keyboard);
  
     glutMainLoop();
  }
  </code></pre>
  
  <p>It should be drawing an equilateral 40x40 triangle at the origin (0,0) in a 400x400 window. Is there something I did wrong?</p>