/**
 * Test XOR emulation with blending.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glew.h>
#include <GL/glut.h>
#include "readtex.c"

#define IMAGE_FILE "../images/arch.rgb"

static int ImgWidth, ImgHeight;
static GLenum ImgFormat;
static GLubyte *Image = NULL;

static int Win;
static int Width = 600, Height = 600;

struct rect
{
   int x0, y0, x1, y1;
};

static struct rect OldRect, NewRect;

static GLboolean ButtonDown = GL_FALSE;
static GLboolean LogicOp = 0*GL_TRUE;


static const GLfloat red[4] = {1.0, 0.2, 0.2, 1.0};
static const GLfloat green[4] = {0.2, 1.0, 0.2, 1.0};
static const GLfloat blue[4] = {0.2, 0.2, 1.0, 1.0};


static void
PrintString(const char *s)
{
   while (*s) {
      glutBitmapCharacter(GLUT_BITMAP_8_BY_13, (int) *s);
      s++;
   }
}


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

   glWindowPos2i((Width - ImgWidth) / 2, (Height - ImgHeight) / 2);
   glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, Image);

   /*
    * Draw 2D XOR rects
    */
   glColor3f(1, 1, 1);

   glWindowPos2i(100, Height - 20);
   PrintString("XOR LogicOp:");
   glLogicOp(GL_XOR);
   glEnable(GL_COLOR_LOGIC_OP);
   glRecti(100, 30, 250, Height - 30);
   glDisable(GL_COLOR_LOGIC_OP);

   glWindowPos2i(Width/2 + 10, Height - 20);
   PrintString("Invert Blending:");
   glBlendFunc(GL_ONE, GL_ONE);
   glBlendEquation(GL_FUNC_SUBTRACT);
   glEnable(GL_BLEND);
   glRecti(Width / 2, 30, Width / 2 + 150, Height - 30);
   glDisable(GL_BLEND);

   glutSwapBuffers();
}


static void
Reshape(int width, int height)
{
   Width = width;
   Height = height;
   glViewport(0, 0, width, height);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(0, Width, 0, Height, -1, 1);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}


static void
Key(unsigned char key, int x, int y)
{
   (void) x;
   (void) y;
   switch (key) {
   case 'b':
   case 'B':
      LogicOp = GL_FALSE;
      break;
   case 'l':
   case 'L':
      LogicOp = GL_TRUE;
      break;
   case 27:
      glutDestroyWindow(Win);
      exit(0);
      break;
   }
   glutPostRedisplay();
}


static void
SpecialKey(int key, int x, int y)
{
   (void) x;
   (void) y;
   switch (key) {
   case GLUT_KEY_UP:
      break;
   case GLUT_KEY_DOWN:
      break;
   case GLUT_KEY_LEFT:
      break;
   case GLUT_KEY_RIGHT:
      break;
   }
   glutPostRedisplay();
}


static void
MouseMotion(int x, int y)
{
   if (ButtonDown) {
      NewRect.x1 = x;
      NewRect.y1 = y;
      glutPostRedisplay();
   }
}


static void
MouseButton(int button, int state, int x, int y)
{
  if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
     ButtonDown = GL_TRUE;
     NewRect.x0 = NewRect.x1 = x;
     NewRect.y0 = NewRect.y1 = y;
     OldRect = NewRect;
  }
  else if (button == GLUT_LEFT_BUTTON && state == GLUT_UP) {
     ButtonDown = GL_FALSE;
  }
}


static void
Init(void)
{
   /*
    * Load image and scale if needed.
    */
   Image = LoadRGBImage(IMAGE_FILE, &ImgWidth, &ImgHeight, &ImgFormat);
   if (!Image) {
      printf("Couldn't read %s\n", IMAGE_FILE);
      exit(0);
   }

   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
   glPixelStorei(GL_PACK_ALIGNMENT, 1);
}


int
main(int argc, char *argv[])
{
   glutInit(&argc, argv);
   glutInitWindowSize(Width, Height);
   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
   Win = glutCreateWindow(argv[0]);
   glewInit();
   glutReshapeFunc(Reshape);
   glutKeyboardFunc(Key);
   glutSpecialFunc(SpecialKey);
   glutMotionFunc(MouseMotion);
   glutMouseFunc(MouseButton);
   glutDisplayFunc(Draw);
   Init();
   glutPostRedisplay();
   glutMainLoop();
   return 0;
}