path: root/progs/demos/texenv.c

/* Copyright (c) Mark J. Kilgard, 1994. */

/**
 * (c) Copyright 1993, Silicon Graphics, Inc.
 * ALL RIGHTS RESERVED
 * Permission to use, copy, modify, and distribute this software for
 * any purpose and without fee is hereby granted, provided that the above
 * copyright notice appear in all copies and that both the copyright notice
 * and this permission notice appear in supporting documentation, and that
 * the name of Silicon Graphics, Inc. not be used in advertising
 * or publicity pertaining to distribution of the software without specific,
 * written prior permission.
 *
 * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "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, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
 * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
 * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
 * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
 * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
 * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
 * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * US Government Users Restricted Rights
 * Use, duplication, or disclosure by the Government is subject to
 * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
 * (c)(1)(ii) of the Rights in Technical Data and Computer Software
 * clause at DFARS 252.227-7013 and/or in similar or successor
 * clauses in the FAR or the DOD or NASA FAR Supplement.
 * Unpublished-- rights reserved under the copyright laws of the
 * United States.  Contractor/manufacturer is Silicon Graphics,
 * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
 *
 * OpenGL(TM) is a trademark of Silicon Graphics, Inc.
 */

/*
 * Demonstrates texture environment modes and internal image formats.
 */

/*
 * Hacked on, updated by Gareth Hughes <gareth@valinux.com>
 */

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

#undef max
#undef min
#define max( a, b )	((a) >= (b) ? (a) : (b))
#define min( a, b )	((a) <= (b) ? (a) : (b))

GLfloat lightCheck[4] = { 0.7, 0.7, 0.7, 1.0 };
GLfloat darkCheck[4] = { 0.3, 0.3, 0.3, 1.0 };

GLfloat labelColor0[4] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat labelColor1[4] = { 1.0, 1.0, 0.4, 1.0 };
GLfloat *labelInfoColor = labelColor0;
GLfloat labelLevelColor0[4] = { 0.8, 0.8, 0.1, 1.0 };
GLfloat labelLevelColor1[4] = { 0.0, 0.0, 0.0, 1.0 };

GLboolean doubleBuffered = GL_FALSE;
GLboolean drawBackground = GL_FALSE;
GLboolean drawBlended = GL_TRUE;
GLboolean drawSmooth = GL_FALSE;
GLboolean drawTextured = GL_TRUE;
GLboolean displayLevelInfo = GL_FALSE;

int textureWidth = 64;
int textureHeight = 64;

int winWidth = 580, winHeight = 720;

struct formatInfo {
   GLenum	baseFormat;
   GLenum	internalFormat;
   char		*name;
};

#define NUM_LUMINANCE_FORMATS	(sizeof(luminanceFormats) / sizeof(luminanceFormats[0]))
struct formatInfo luminanceFormats[] =
{
   { GL_LUMINANCE, GL_LUMINANCE, "LUMINANCE" },
   { GL_LUMINANCE, GL_LUMINANCE4, "LUMINANCE4" },
   { GL_LUMINANCE, GL_LUMINANCE8, "LUMINANCE8" },
   { GL_LUMINANCE, GL_LUMINANCE12, "LUMINANCE12" },
   { GL_LUMINANCE, GL_LUMINANCE16, "LUMINANCE16" },
};

#define NUM_ALPHA_FORMATS	(sizeof(alphaFormats) / sizeof(alphaFormats[0]))
struct formatInfo alphaFormats[] =
{
   { GL_ALPHA, GL_ALPHA, "ALPHA" },
   { GL_ALPHA, GL_ALPHA4, "ALPHA4" },
   { GL_ALPHA, GL_ALPHA8, "ALPHA8" },
   { GL_ALPHA, GL_ALPHA12, "ALPHA12" },
   { GL_ALPHA, GL_ALPHA16, "ALPHA16" },
};

#define NUM_INTENSITY_FORMATS	(sizeof(intensityFormats) / sizeof(intensityFormats[0]))
struct formatInfo intensityFormats[] =
{
   { GL_INTENSITY, GL_INTENSITY, "INTENSITY" },
   { GL_INTENSITY, GL_INTENSITY4, "INTENSITY4" },
   { GL_INTENSITY, GL_INTENSITY8, "INTENSITY8" },
   { GL_INTENSITY, GL_INTENSITY12, "INTENSITY12" },
   { GL_INTENSITY, GL_INTENSITY16, "INTENSITY16" },
};

#define NUM_LUMINANCE_ALPHA_FORMATS	(sizeof(luminanceAlphaFormats) / sizeof(luminanceAlphaFormats[0]))
struct formatInfo luminanceAlphaFormats[] =
{
   { GL_LUMINANCE_ALPHA, GL_LUMINANCE_ALPHA, "LUMINANCE_ALPHA" },
   { GL_LUMINANCE_ALPHA, GL_LUMINANCE4_ALPHA4, "LUMINANCE4_ALPHA4" },
   { GL_LUMINANCE_ALPHA, GL_LUMINANCE6_ALPHA2, "LUMINANCE6_ALPHA2" },
   { GL_LUMINANCE_ALPHA, GL_LUMINANCE8_ALPHA8, "LUMINANCE8_ALPHA8" },
   { GL_LUMINANCE_ALPHA, GL_LUMINANCE12_ALPHA4, "LUMINANCE12_ALPHA4" },
   { GL_LUMINANCE_ALPHA, GL_LUMINANCE12_ALPHA12, "LUMINANCE12_ALPHA12" },
   { GL_LUMINANCE_ALPHA, GL_LUMINANCE16_ALPHA16, "LUMINANCE16_ALPHA16" },
};

#define NUM_RGB_FORMATS		(sizeof(rgbFormats) / sizeof(rgbFormats[0]))
struct formatInfo rgbFormats[] =
{
   { GL_RGB, GL_RGB, "RGB" },
   { GL_RGB, GL_R3_G3_B2, "R3_G3_B2" },
   { GL_RGB, GL_RGB4, "RGB4" },
   { GL_RGB, GL_RGB5, "RGB5" },
   { GL_RGB, GL_RGB8, "RGB8" },
   { GL_RGB, GL_RGB10, "RGB10" },
   { GL_RGB, GL_RGB12, "RGB12" },
   { GL_RGB, GL_RGB16, "RGB16" },
};

#define NUM_RGBA_FORMATS	(sizeof(rgbaFormats) / sizeof(rgbaFormats[0]))
struct formatInfo rgbaFormats[] =
{
   { GL_RGBA, 4, "RGBA" },
   { GL_RGBA, GL_RGBA2, "RGBA2" },
   { GL_RGBA, GL_RGBA4, "RGBA4" },
   { GL_RGBA, GL_RGB5_A1, "RGB5_A1" },
   { GL_RGBA, GL_RGBA8, "RGBA8" },
   { GL_RGBA, GL_RGB10_A2, "RGB10_A2" },
   { GL_RGBA, GL_RGBA12, "RGBA12" },
   { GL_RGBA, GL_RGBA16, "RGBA16" },
};

struct baseFormatInfo {
   struct	formatInfo *format;
   int		current, number;
};

#define NUM_BASE_FORMATS	(sizeof(baseFormats) / sizeof(baseFormats[0]))
int baseFormat;
struct baseFormatInfo baseFormats[] =
{
   { luminanceFormats, 0, NUM_LUMINANCE_FORMATS },
   { alphaFormats, 0, NUM_ALPHA_FORMATS },
   { intensityFormats, 0, NUM_INTENSITY_FORMATS },
   { luminanceAlphaFormats, 0, NUM_LUMINANCE_ALPHA_FORMATS },
   { rgbFormats, 0, NUM_RGB_FORMATS },
   { rgbaFormats, 0, NUM_RGBA_FORMATS },
};

#define NUM_ENV_COLORS		(sizeof(envColors) / sizeof(envColors[0]))
int envColor;
GLfloat envColors[][4] =
{
   { 0.0, 0.0, 0.0, 1.0 },
   { 1.0, 0.0, 0.0, 1.0 },
   { 0.0, 1.0, 0.0, 1.0 },
   { 0.0, 0.0, 1.0, 1.0 },
   { 1.0, 1.0, 1.0, 1.0 },
};

struct envModeInfo {
   GLenum	mode;
   char		*name;
};

/* allow for run-time check for GL_EXT_texture_env_add */
int NUM_ENV_MODES = 5;
struct envModeInfo envModes[] =
{
   { GL_REPLACE, "REPLACE" },
   { GL_MODULATE, "MODULATE" },
   { GL_BLEND, "BLEND" },
   { GL_DECAL, "DECAL" },
#if GL_EXT_texture_env_add
   { GL_ADD, "ADD" },
#endif
};

static void checkErrors( void )
{
   GLenum error;

   return;

   while ( (error = glGetError()) != GL_NO_ERROR ) {
      fprintf( stderr, "Error: %s\n", (char *) gluErrorString( error ) );
   }
}

static void drawString( char *string, GLfloat x, GLfloat y, GLfloat color[4] )
{
   glColor4fv( color );
   glRasterPos2f( x, y );

   while ( *string ) {
      glutBitmapCharacter( GLUT_BITMAP_TIMES_ROMAN_10, *string );
      string++;
   }
}

static void drawStringOutline( char *string, GLfloat x, GLfloat y,
			       GLfloat color[4], GLfloat outline[4] )
{
   drawString( string, x - 1, y, outline );
   drawString( string, x + 1, y, outline );
   drawString( string, x, y - 1, outline );
   drawString( string, x, y + 1, outline );
   drawString( string, x, y, color );
}

static void begin2D( int width, int height )
{
   glMatrixMode( GL_PROJECTION );

   glPushMatrix();
   glLoadIdentity();

   glOrtho( 0, width, 0, height, -1, 1 );
   glMatrixMode( GL_MODELVIEW );

   glPushMatrix();
   glLoadIdentity();
}

static void end2D( void )
{
   glMatrixMode( GL_PROJECTION );
   glPopMatrix();
   glMatrixMode( GL_MODELVIEW );
   glPopMatrix();
}

static void initialize( void )
{
   glMatrixMode( GL_PROJECTION );
   glLoadIdentity();

   glOrtho( -1.5, 1.5, -1.5, 1.5, -1.5, 1.5 );

   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();

   glShadeModel( GL_FLAT );
}

/* ARGSUSED1 */
static void keyboard( unsigned char c, int x, int y )
{
   switch ( c ) {
   case 'c':
      envColor = ++envColor % (int) NUM_ENV_COLORS;
      break;
   case 'g':
      drawBackground = !drawBackground;
      break;
   case 'b':
      drawBlended = !drawBlended;
      break;
   case 's':
      drawSmooth = !drawSmooth;
      break;
   case 't':
      drawTextured = !drawTextured;
      break;
   case 'i':
      displayLevelInfo = !displayLevelInfo;
      break;
   case 27:             /* Escape key should force exit. */
      exit(0);
      break;
   default:
      break;
   }
   glutPostRedisplay();
}

/* ARGSUSED1 */
static void special( int key, int x, int y )
{
   switch ( key ) {
   case GLUT_KEY_DOWN:
      if ( ++baseFormat > NUM_BASE_FORMATS - 1 ) {
	 baseFormat = 0;
      }
      break;
   case GLUT_KEY_UP:
      if ( --baseFormat < 0 ) {
	 baseFormat = NUM_BASE_FORMATS - 1;
      }
      break;
   case GLUT_KEY_LEFT:
      --baseFormats[baseFormat].current;
      if ( baseFormats[baseFormat].current < 0 ) {
	 baseFormats[baseFormat].current = baseFormats[baseFormat].number - 1;
      }
      break;
   case GLUT_KEY_RIGHT:
      ++baseFormats[baseFormat].current;
      if ( baseFormats[baseFormat].current > baseFormats[baseFormat].number - 1 ) {
	 baseFormats[baseFormat].current = 0;
      }
      break;
   default:
      break;
   }
   glutPostRedisplay();
}

static void
reshape( int w, int h )
{
   winWidth = w;
   winHeight = h;
   /* No need to call glViewPort here since "draw" calls it! */
}

static void loadTexture( int width, int height, struct formatInfo *format )
{
   int		luminanceSize = 0;
   int		alphaSize = 0;
   int		rgbSize = 0;
   GLenum	textureFormat;
   GLubyte	*texImage, *p;
   int		elementsPerGroup, elementSize, groupSize, rowSize;
   int		i, j;

   switch ( format->baseFormat ) {
   case GL_LUMINANCE:
      luminanceSize = 1;
      textureFormat = GL_LUMINANCE;
      break;
   case GL_INTENSITY:
      luminanceSize = 1;
      textureFormat = GL_INTENSITY;
      break;
   case GL_ALPHA:
      alphaSize = 1;
      textureFormat = GL_ALPHA;
      break;
   case GL_LUMINANCE_ALPHA:
      luminanceSize = 1;
      alphaSize = 1;
      textureFormat = GL_LUMINANCE_ALPHA;
      break;
   case GL_RGB:
      rgbSize = 3;
      textureFormat = GL_RGB;
      break;
   case GL_RGBA:
      rgbSize = 3;
      alphaSize = 1;
      textureFormat = GL_RGBA;
      break;
   default:
      fprintf(stderr, "bad internal format info\n");
      return;
   }

   elementsPerGroup = luminanceSize + alphaSize + rgbSize;
   elementSize = sizeof(GLubyte);
   groupSize = elementsPerGroup * elementSize;
   rowSize = width * groupSize;

   if ( (texImage = (GLubyte *) malloc( height * rowSize ) ) == NULL ) {
      fprintf( stderr, "texture malloc failed\n" );
      return;
   }

   for ( i = 0 ; i < height ; i++ )
   {
      p = texImage + i * rowSize;

      for ( j = 0 ; j < width ; j++ )
      {
	 if ( luminanceSize > 0 )
	 {
	    /**
	     ** +-----+-----+
	     ** |     |     |
	     ** |  W  | LG  |
	     ** |     |     |
	     ** +-----+-----+
	     ** |     |     |
	     ** | DG  |  B  |
	     ** |     |     |
	     ** +-----+-----+
	     **/
	    if ( i > height / 2 ) {
	       if ( j < width / 2 ) {
		  p[0] = 0xff;
	       } else {
		  p[0] = 0xaa;
	       }
	    } else {
	       if ( j < width / 2 ) {
		  p[0] = 0x55;
	       } else {
		  p[0] = 0x00;
	       }
	    }
	    p += elementSize;
	 }

	 if ( rgbSize > 0 )
	 {
	    /**
	     ** +-----+-----+
	     ** |     |     |
	     ** |  R  |  G  |
	     ** |     |     |
	     ** +-----+-----+
	     ** |     |     |
	     ** |  Y  |  B  |
	     ** |     |     |
	     ** +-----+-----+
	     **/
	    if ( i > height / 2 ) {
	       if ( j < width / 2 ) {
		  p[0] = 0xff;
		  p[1] = 0x00;
		  p[2] = 0x00;
	       } else {
		  p[0] = 0x00;
		  p[1] = 0xff;
		  p[2] = 0x00;
	       }
	    } else {
	       if ( j < width / 2 ) {
		  p[0] = 0xff;
		  p[1] = 0xff;
		  p[2] = 0x00;
	       } else {
		  p[0] = 0x00;
		  p[1] = 0x00;
		  p[2] = 0xff;
	       }
	    }
	    p += 3 * elementSize;
	 }

	 if ( alphaSize > 0 )
	 {
	    /**
	     ** +-----------+
	     ** |     W     |
	     ** |  +-----+  |
	     ** |  |     |  |
	     ** |  |  B  |  |
	     ** |  |     |  |
	     ** |  +-----+  |
	     ** |           |
	     ** +-----------+
	     **/
	    int i2 = i - height / 2;
	    int j2 = j - width / 2;
	    int h8 = height / 8;
	    int w8 = width / 8;
	    if ( -h8 <= i2 && i2 <= h8 && -w8 <= j2 && j2 <= w8 ) {
	       p[0] = 0x00;
	    } else if ( -2 * h8 <= i2 && i2 <= 2 * h8 && -2 * w8 <= j2 && j2 <= 2 * w8 ) {
	       p[0] = 0x55;
	    } else if ( -3 * h8 <= i2 && i2 <= 3 * h8 && -3 * w8 <= j2 && j2 <= 3 * w8 ) {
	       p[0] = 0xaa;
	    } else {
	       p[0] = 0xff;
	    }
	    p += elementSize;
	 }
      }
   }

   glTexImage2D( GL_TEXTURE_2D, 0,
		 format->internalFormat, width, height, 0,
		 textureFormat, GL_UNSIGNED_BYTE, texImage );

   free( texImage );
}

static void drawCheck( int w, int h, GLfloat lightCheck[4], GLfloat darkCheck[4] )
{
   float	dw = 2.0 / w;
   float	dh = 2.0 / h;
   int		i, j;

   for ( i = 0 ; i < w ; i++ ) {
      GLfloat x0 = -1.0 + i * dw;
      GLfloat x1 = x0 + dw;

      glBegin( GL_QUAD_STRIP );

      for ( j = 0 ; j <= h ; j++ ) {
	 GLfloat y = -1.0 + j * dh;

	 if ( (i ^ j) & 1 ) {
	    glColor4fv( lightCheck );
	 } else {
	    glColor4fv( darkCheck );
	 }

	 glVertex2f( x0, y );
	 glVertex2f( x1, y );
      }

      glEnd();
   }
}

static void drawSample( int x, int y, int w, int h,
			struct formatInfo *format, struct envModeInfo *envMode )
{
   glViewport( x, y, w, h );
   glScissor( x, y, w, h );

   glClearColor( 0.1, 0.1, 0.1, 1.0 );
   glClear( GL_COLOR_BUFFER_BIT );

   begin2D( w, h );
   drawString( format->name, 10, h - 15, labelInfoColor );
   drawString( envMode->name, 10, 5, labelInfoColor );
   end2D();

   glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, envMode->mode );
   glTexEnvfv( GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, envColors[envColor] );

   glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
   glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

   glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP );
   glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP );

   loadTexture( textureWidth, textureHeight, format );

   if ( drawBackground ) {
      drawCheck( 15, 15, lightCheck, darkCheck );
   }
   if ( drawBlended ) {
      glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
      glEnable( GL_BLEND );
   }
   if ( drawSmooth ) {
      glShadeModel( GL_SMOOTH );
   }
   if ( drawTextured ) {
      glEnable( GL_TEXTURE_2D );
   }

   glBegin( GL_QUADS );
      glColor4f( 1.0, 0.0, 0.0, 1.0 );
      glTexCoord2f( 0.0, 0.0 );
      glVertex2f( -0.8, -0.8 );

      glColor4f( 0.0, 1.0, 0.0, 1.0 );
      glTexCoord2f( 1.0, 0.0 );
      glVertex2f( 0.8, -0.8 );

      glColor4f( 0.0, 0.0, 1.0, 1.0 );
      glTexCoord2f( 1.0, 1.0 );
      glVertex2f( 0.8, 0.8 );

      glColor4f( 1.0, 1.0, 1.0, 1.0 );
      glTexCoord2f( 0.0, 1.0 );
      glVertex2f( -0.8, 0.8 );
   glEnd();

   glDisable( GL_BLEND );
   glShadeModel( GL_FLAT );
   glDisable( GL_TEXTURE_2D );

   if ( envMode->mode == GL_DECAL &&
        (format->baseFormat == GL_ALPHA ||
         format->baseFormat == GL_LUMINANCE ||
         format->baseFormat == GL_LUMINANCE_ALPHA ||
         format->baseFormat == GL_INTENSITY)) {
      /* undefined format/mode combination */
      begin2D( w, h );
      drawStringOutline( "UNDEFINED MODE", 15, h / 2,
                         labelLevelColor0, labelLevelColor1 );
      end2D();
   }
   else if ( displayLevelInfo ) {
      GLint width, height, border, components;
      GLint redSize, greenSize, blueSize, alphaSize;
      GLint luminanceSize, intensitySize;
      char buf[255];

      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &width );
      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &height );
      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_BORDER, &border );
      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_COMPONENTS, &components );
      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_RED_SIZE, &redSize );
      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_GREEN_SIZE, &greenSize );
      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_BLUE_SIZE, &blueSize );
      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_ALPHA_SIZE, &alphaSize );
      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_LUMINANCE_SIZE, &luminanceSize );
      glGetTexLevelParameteriv( GL_TEXTURE_2D, 0, GL_TEXTURE_INTENSITY_SIZE, &intensitySize );

      begin2D( w, h );
      sprintf( buf, "dimensions: %d x %d", width, height );
      drawStringOutline( buf, 15, h / 2 + 20, labelLevelColor0, labelLevelColor1 );

      sprintf( buf, "border: %d", border );
      drawStringOutline( buf, 15, h / 2 + 10, labelLevelColor0, labelLevelColor1 );

      sprintf( buf, "components: 0x%04X", components );
      drawStringOutline( buf, 15, h / 2, labelLevelColor0, labelLevelColor1 );

      sprintf( buf, "sizes:" );
      drawStringOutline( buf, 15, h / 2 - 10, labelLevelColor0, labelLevelColor1 );

      sprintf( buf, "  %d / %d / %d / %d / %d / %d",
	       redSize, greenSize, blueSize, alphaSize,
	       luminanceSize, intensitySize );
      drawStringOutline( buf, 15, h / 2 - 20, labelLevelColor0, labelLevelColor1 );

      end2D();
   }
}

static void display( void )
{
   int		numX = NUM_ENV_MODES, numY = NUM_BASE_FORMATS;
   float	xBase = (float) winWidth * 0.01;
   float	xOffset = (winWidth - xBase) / numX;
   float	xSize = max( xOffset - xBase, 1 );
   float	yBase = (float) winHeight * 0.01;
   float	yOffset = (winHeight - yBase) / numY;
   float	ySize = max( yOffset - yBase, 1 );
   float	x, y;
   int		i, j;

   glViewport( 0, 0, winWidth, winHeight );
   glDisable( GL_SCISSOR_TEST );
   glClearColor( 0.0, 0.0, 0.0, 0.0 );
   glClear( GL_COLOR_BUFFER_BIT );
   glEnable( GL_SCISSOR_TEST );

   x = xBase;
   y = (winHeight - 1) - yOffset;

   for ( i = 0 ; i < NUM_BASE_FORMATS ; i++ )
   {
      struct formatInfo *format;

      if ( i == baseFormat ) {
	 labelInfoColor = labelColor1;
      } else {
	 labelInfoColor = labelColor0;
      }

      format = &baseFormats[i].format[baseFormats[i].current];

      for ( j = 0 ; j < NUM_ENV_MODES ; j++ ) {
	 struct envModeInfo *envMode;

	 envMode = &envModes[j];
	 drawSample( x, y, xSize, ySize, format, envMode );
	 x += xOffset;
      }

      x = xBase;
      y -= yOffset;
   }

   if ( doubleBuffered ) {
      glutSwapBuffers();
   } else {
      glFlush();
   }

   checkErrors();
}

static void usage( char *name )
{
   fprintf( stderr, "usage: %s [ options ]\n", name );
   fprintf( stderr, "\n" );
   fprintf( stderr, "options:\n" );
   fprintf( stderr, "    -sb    single buffered\n" );
   fprintf( stderr, "    -db    double buffered\n" );
   fprintf( stderr, "    -info  print OpenGL driver info\n" );
}

static void instructions( void )
{
   fprintf( stderr, "texenv - texture environment and internal format test\n" );
   fprintf( stderr, "\n" );
   fprintf( stderr, "  [c] - cycle through background colors\n" );
   fprintf( stderr, "  [g] - toggle background\n" );
   fprintf( stderr, "  [b] - toggle blend\n" );
   fprintf( stderr, "  [s] - toggle smooth shading\n" );
   fprintf( stderr, "  [t] - toggle texturing\n" );
   fprintf( stderr, "  [i] - toggle information display\n" );
}

int main( int argc, char *argv[] )
{
   GLboolean info = GL_FALSE;
   int i;

   glutInit( &argc, argv );

   for ( i = 1 ; i < argc ; i++ ) {
      if ( !strcmp( "-sb", argv[i] ) ) {
	 doubleBuffered = GL_FALSE;
      } else if ( !strcmp( "-db", argv[i] ) ) {
	 doubleBuffered = GL_TRUE;
      } else if ( !strcmp( "-info", argv[i] ) ) {
	 info = GL_TRUE;
      } else {
	 usage( argv[0] );
	 exit( 1 );
      }
   }

   if ( doubleBuffered ) {
      glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
   } else {
      glutInitDisplayMode( GLUT_RGB | GLUT_SINGLE );
   }

   glutInitWindowSize( winWidth, winHeight );
   glutCreateWindow( "Texture Environment Test" );

   initialize();
   instructions();

   if ( info ) {
      printf( "\n" );
      printf( "GL_RENDERER   = %s\n", (char *) glGetString( GL_RENDERER ) );
      printf( "GL_VERSION    = %s\n", (char *) glGetString( GL_VERSION ) );
      printf( "GL_VENDOR     = %s\n", (char *) glGetString( GL_VENDOR ) ) ;
      printf( "GL_EXTENSIONS = %s\n", (char *) glGetString( GL_EXTENSIONS ) );
   }

#if GL_EXT_texture_env_add
   if ( !glutExtensionSupported( "GL_EXT_texture_env_add" ) ) {
      fprintf( stderr, "missing extension: GL_EXT_texture_env_add\n" );
      NUM_ENV_MODES--;
   }
#endif

   glutDisplayFunc( display );
   glutReshapeFunc( reshape );
   glutKeyboardFunc( keyboard );
   glutSpecialFunc( special );
   glutMainLoop();

   return 0;
}