mesa/progs/trivial/dlist-degenerate.c

/**
 * Test display list corner cases.
 */


#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>


static int Win;
static GLfloat Xrot = 0, Yrot = 0, Zrot = 0;
static GLboolean Anim = GL_FALSE;
static GLuint List1 = 0, List2 = 0;


static void
Idle(void)
{
   Xrot += 3.0;
   Yrot += 4.0;
   Zrot += 2.0;
   glutPostRedisplay();
}


static void
Draw(void)
{
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

   glPushMatrix();
   glRotatef(Xrot, 1, 0, 0);
   glRotatef(Yrot, 0, 1, 0);
   glRotatef(Zrot, 0, 0, 1);

   glCallList(List1);
   glCallList(List2);

   glPopMatrix();

   glutSwapBuffers();
}


static void
Reshape(int width, int height)
{
   glViewport(0, 0, width, height);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 25.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   glTranslatef(0.0, 0.0, -15.0);
}


static void
Key(unsigned char key, int x, int y)
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case 'a':
         Anim = !Anim;
         if (Anim)
            glutIdleFunc(Idle);
         else
            glutIdleFunc(NULL);
         break;
      case 'z':
         Zrot -= step;
         break;
      case 'Z':
         Zrot += step;
         break;
      case 27:
         glutDestroyWindow(Win);
         exit(0);
         break;
   }
   glutPostRedisplay();
}


static void
SpecialKey(int key, int x, int y)
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case GLUT_KEY_UP:
         Xrot -= step;
         break;
      case GLUT_KEY_DOWN:
         Xrot += step;
         break;
      case GLUT_KEY_LEFT:
         Yrot -= step;
         break;
      case GLUT_KEY_RIGHT:
         Yrot += step;
         break;
   }
   glutPostRedisplay();
}


static void
Init(void)
{
   /* List1: start of primitive */
   List1 = glGenLists(1);
   glNewList(List1, GL_COMPILE);
     glBegin(GL_POLYGON);
     glVertex2f(-1, -1);
     glVertex2f( 1, -1);
   glEndList();

   /* List2: end of primitive */
   List2 = glGenLists(1);
   glNewList(List2, GL_COMPILE);
     glVertex2f( 1, 1);
     glVertex2f(-1, 1);
     glEnd();
   glEndList();

   glEnable(GL_DEPTH_TEST);
}


int
main(int argc, char *argv[])
{
   glutInit(&argc, argv);
   glutInitWindowPosition(0, 0);
   glutInitWindowSize(400, 400);
   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
   Win = glutCreateWindow(argv[0]);
   glutReshapeFunc(Reshape);
   glutKeyboardFunc(Key);
   glutSpecialFunc(SpecialKey);
   glutDisplayFunc(Draw);
   if (Anim)
      glutIdleFunc(Idle);
   Init();
   glutMainLoop();
   return 0;
}