progs/trivial/tri-mask-tri.c

/*
 * Copyright (c) 1991, 1992, 1993 Silicon Graphics, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software and
 * its documentation for any purpose is hereby granted without fee, provided
 * that (i) the above copyright notices and this permission notice appear in
 * all copies of the software and related documentation, and (ii) the name of
 * Silicon Graphics may not be used in any advertising or
 * publicity relating to the software without the specific, prior written
 * permission of Silicon Graphics.
 *
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF
 * ANY KIND,
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 *
 * IN NO EVENT SHALL SILICON GRAPHICS BE LIABLE FOR
 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

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


GLint Width = 250, Height = 250;
GLenum doubleBuffer;
GLint Win;
GLboolean Rmask = GL_TRUE, Gmask = GL_FALSE, Bmask = GL_TRUE;


static void Init(void)
{
   fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
   fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
   fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
   glClearColor(0.0, 0.0, 1.0, 0.0);
}

static void Reshape(int width, int height)
{
   glViewport(0, 0, (GLint)width, (GLint)height);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
   glMatrixMode(GL_MODELVIEW);
}

static void Key(unsigned char key, int x, int y)
{
   switch (key) {
   case 'r':
      Rmask = !Rmask;
      break;
   case 'g':
      Gmask = !Gmask;
      break;
   case 'b':
      Bmask = !Bmask;
      break;
   case 27:
      glutDestroyWindow(Win);
      exit(1);
   default:
      return;
   }
   glutPostRedisplay();
}

static void Draw(void)
{
   printf("ColorMask = %d, %d, %d\n", Rmask, Gmask, Bmask);
   glColorMask(1,1,1,1);

   glClear(GL_COLOR_BUFFER_BIT); 

   /* right triangle: green */
   glBegin(GL_TRIANGLES);
   glColor3f(0,1,0); 
   glVertex3f( 0.9, -0.9, -30.0);
   glVertex3f( 0.9,  0.9, -30.0);
   glVertex3f(-0.9,  0.0, -30.0);
   glEnd();

   glColorMask(Rmask, Gmask, Bmask, 0);

   /* left triangle: white&mask: purple   middle region: white */
   glBegin(GL_TRIANGLES);
   glColor3f(1,1,1); 
   glVertex3f(-0.9, -0.9, -30.0);
   glVertex3f(-0.9,  0.9, -30.0);
   glVertex3f( 0.9,  0.0, -30.0);
   glEnd();

   glDisable(GL_SCISSOR_TEST);

   glFlush();

   if (doubleBuffer) {
      glutSwapBuffers();
   }
}

static GLenum Args(int argc, char **argv)
{
   GLint i;

   doubleBuffer = GL_FALSE;

   for (i = 1; i < argc; i++) {
      if (strcmp(argv[i], "-sb") == 0) {
         doubleBuffer = GL_FALSE;
      }
      else if (strcmp(argv[i], "-db") == 0) {
         doubleBuffer = GL_TRUE;
      }
      else {
         fprintf(stderr, "%s (Bad option).\n", argv[i]);
         return GL_FALSE;
      }
   }
   return GL_TRUE;
}


int main(int argc, char **argv)
{
   GLenum type;

   glutInit(&argc, argv);

   if (Args(argc, argv) == GL_FALSE) {
      exit(1);
   }

   type = GLUT_RGB;
   type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;

   glutInitWindowPosition(100, 0); glutInitWindowSize(Width, Height);
   glutInitDisplayMode(type);
   Win = glutCreateWindow(*argv);
   Init();
   glutReshapeFunc(Reshape);
   glutKeyboardFunc(Key);
   glutDisplayFunc(Draw);
   glutMainLoop();
   return 0;
}