mesa/progs/trivial/quad-tex-alpha.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>


#define CI_OFFSET_1 16
#define CI_OFFSET_2 32


GLenum doubleBuffer;

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));
   fflush(stderr);

    glClearColor(0.0, 0.0, 1.0, 0.0);

#define SIZE 16
   {
      GLubyte tex2d[SIZE][SIZE][4];
      GLint s, t;

      for (s = 0; s < SIZE; s++) {
	 for (t = 0; t < SIZE; t++) {
	    tex2d[t][s][0] = (s < SIZE/2) ? 0 : 255;
	    tex2d[t][s][1] = (t < SIZE/2) ? 0 : 255;
	    tex2d[t][s][2] = 0;
	    tex2d[t][s][3] = ((t^s) & 3) * 63;
	 }
      }

      glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
      glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_REPEAT);
      glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
      glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

      glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
      glTexImage2D(GL_TEXTURE_2D, 0, 4, SIZE, SIZE, 0,
		   GL_RGBA, GL_UNSIGNED_BYTE, tex2d);
      glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
      glEnable(GL_TEXTURE_2D);
   }
}

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 27:
	exit(1);
      default:
	break;
    }

    glutPostRedisplay();
}

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

   glDisable(GL_DEPTH_TEST);
   glDisable(GL_STENCIL_TEST);
   glEnable(GL_ALPHA_TEST);
   glAlphaFunc(GL_GEQUAL, 0.5);

   glBegin(GL_QUADS);
   glTexCoord2f(1,0); 
   glVertex3f( 0.9, -0.9, -30.0);
   glTexCoord2f(1,1); 
   glVertex3f( 0.9,  0.9, -30.0);
   glTexCoord2f(0,1); 
   glVertex3f(-0.9,  0.9, -30.0);
   glTexCoord2f(0,0); 
   glVertex3f(-0.9,  -0.9, -30.0);
   glEnd();


   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);
    }

    glutInitWindowPosition(100, 0); glutInitWindowSize( 250, 250);

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

    if (glutCreateWindow(*argv) == GL_FALSE) {
	exit(1);
    }

    Init();

    glutReshapeFunc(Reshape);
    glutKeyboardFunc(Key);
    glutDisplayFunc(Draw);
    glutMainLoop();
	return 0;
}