/*
 * ** blendeq.c - Demonstrates the use of the blend_minmax, blend_subtract,
 * **    and blend_logic_op extensions using glBlendEquationEXT.
 * **
 * **    Over a two-color backround, draw rectangles using twelve blend
 * **    options.  The values are read back as UNSIGNED_BYTE and printed
 * **    in hex over each value.  These values are useful for logic
 * **    op comparisons when channels are 8 bits deep.
 */

#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include "gltk.h"

GLenum doubleBuffer, directRender;
static int dithering = 0;
static int doPrint = 1;
static int deltaY;
GLint windW, windH;
GLuint bitmapBase;

static void Init(void)
{
  bitmapBase = glGenLists(256);
  if (tkCreateBitmapFont(bitmapBase) == GL_FALSE) {
    tkQuit();
  }

  glDisable(GL_DITHER);
  glShadeModel(GL_FLAT);
}

static void Reshape(int width, int height)
{

  windW = (GLint) width;
  windH = (GLint) height;

  glViewport(0, 0, (GLint) width, (GLint) height);
  deltaY = windH / 16;

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(0, windW, 0, windH);
  glMatrixMode(GL_MODELVIEW);
}

static GLenum Key(int key, GLenum mask)
{

  switch (key) {
    case TK_ESCAPE:
      tkQuit();
    case TK_d:
      dithering = !dithering;
      break;
    default:
      return GL_FALSE;
  }
  return GL_TRUE;
}

static void PrintColorStrings(void)
{
  GLubyte ubbuf[3];
  int i, xleft, xright;
  char colorString[18];

  xleft = 5 + windW / 4;
  xright = 5 + windW / 2;

  for (i = windH - deltaY + 4; i > 0; i -= deltaY) {
    glReadPixels(xleft, i + 10, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, ubbuf);
    sprintf(colorString, "(0x%x, 0x%x, 0x%x)",
	    ubbuf[0], ubbuf[1], ubbuf[2]);
    glRasterPos2f(xleft, i);
    tkDrawStr(bitmapBase, colorString);
    glReadPixels(xright, i + 10, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, ubbuf);
    sprintf(colorString, "(0x%x, 0x%x, 0x%x)",
	    ubbuf[0], ubbuf[1], ubbuf[2]);
    glRasterPos2f(xright, i);
    tkDrawStr(bitmapBase, colorString);
  }
}

static void Draw(void)
{
  int stringOffset = 5, stringx = 8;
  int x1, x2, xleft, xright;
  int i;

  (dithering) ? glEnable(GL_DITHER) : glDisable(GL_DITHER);
  glDisable(GL_BLEND);

  glClearColor(0.5, 0.6, 0.1, 1.0);
  glClear(GL_COLOR_BUFFER_BIT);

  /*
   * Draw background 
   */
  glColor3f(0.1, 0.1, 1.0);
  glRectf(0.0, 0.0, windW / 2, windH);

  /*
   * Draw labels 
   */
  glColor3f(0.8, 0.8, 0.0);
  i = windH - deltaY + stringOffset;
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "SOURCE");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "DEST");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "min");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "max");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "subtract");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "reverse_subtract");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "clear");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "set");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "copy");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "noop");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "and");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "invert");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "or");
  glRasterPos2f(stringx, i);
  i -= deltaY;
  tkDrawStr(bitmapBase, "xor");

  i = windH - deltaY;
  x1 = windW / 4;
  x2 = 3 * windW / 4;
  xleft = 5 + windW / 4;
  xright = 5 + windW / 2;

  /*
   * Draw foreground color for comparison 
   */
  glColor3f(0.9, 0.2, 0.8);
  glRectf(x1, i, x2, i + deltaY);

  /*
   * Leave one rectangle of background color 
   */

  /*
   * Begin test cases 
   */
  glEnable(GL_BLEND);
  glBlendFunc(GL_ONE, GL_ONE);

  i -= 2 * deltaY;
  glBlendEquationEXT(GL_MIN_EXT);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_MAX_EXT);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_FUNC_SUBTRACT_EXT);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_FUNC_REVERSE_SUBTRACT_EXT);
  glRectf(x1, i, x2, i + deltaY);

  glBlendFunc(GL_ONE, GL_ZERO);
  i -= deltaY;
  glBlendEquationEXT(GL_LOGIC_OP);
  glLogicOp(GL_CLEAR);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_LOGIC_OP);
  glLogicOp(GL_SET);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_LOGIC_OP);
  glLogicOp(GL_COPY);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_LOGIC_OP);
  glLogicOp(GL_NOOP);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_LOGIC_OP);
  glLogicOp(GL_AND);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_LOGIC_OP);
  glLogicOp(GL_INVERT);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_LOGIC_OP);
  glLogicOp(GL_OR);
  glRectf(x1, i, x2, i + deltaY);

  i -= deltaY;
  glBlendEquationEXT(GL_LOGIC_OP);
  glLogicOp(GL_XOR);
  glRectf(x1, i, x2, i + deltaY);
  glRectf(x1, i + 10, x2, i + 5);

  if (doPrint) {
    glDisable(GL_BLEND);
    glColor3f(1.0, 1.0, 1.0);
    PrintColorStrings();
  }
  glFlush();

  if (doubleBuffer) {
    tkSwapBuffers();
  }

}

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

  doubleBuffer = GL_FALSE;
  directRender = GL_TRUE;

  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 if (strcmp(argv[i], "-dr") == 0) {
      directRender = GL_TRUE;
    }
    else if (strcmp(argv[i], "-ir") == 0) {
      directRender = GL_FALSE;
    }
    else {
      printf("%s (Bad option).\n", argv[i]);
      return GL_FALSE;
    }
  }
  return GL_TRUE;
}

void main(int argc, char **argv)
{
  GLenum type;
  char *s;
  char *extName1 = "GL_EXT_blend_logic_op";
  char *extName2 = "GL_EXT_blend_minmax";
  char *extName3 = "GL_EXT_blend_subtract";

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

  tkInitPosition(0, 0, 800, 400);

  type = TK_RGB;
  type |= (doubleBuffer) ? TK_DOUBLE : TK_SINGLE;
  type |= (directRender) ? TK_DIRECT : TK_INDIRECT;
  tkInitDisplayMode(type);

  if (tkInitWindow("Blend Equation") == GL_FALSE) {
    tkQuit();
  }

  /*
   * Make sure blend_logic_op extension is there. 
   */
  s = (char *)glGetString(GL_EXTENSIONS);
  if (!s)
    tkQuit();
  if (strstr(s, extName1) == 0) {
    printf("Blend_logic_op extension is not present.\n");
    tkQuit();
  }
  if (strstr(s, extName2) == 0) {
    printf("Blend_minmax extension is not present.\n");
    tkQuit();
  }
  if (strstr(s, extName3) == 0) {
    printf("Blend_subtract extension is not present.\n");
    tkQuit();
  }

  Init();

  tkExposeFunc(Reshape);
  tkReshapeFunc(Reshape);
  tkKeyDownFunc(Key);
  tkDisplayFunc(Draw);
  tkExec();
}