/*
   Sample Program Using Color Index "Overlay"

   VIZA 652            F. Parke		12/01/97
*/

#include <stdio.h>	/* define standard I/O routines */
#include <GL/gl.h>	/* define OpenGL graphics routines */
#include <GL/glu.h>	/* define OpenGL utility routines */
#include <glut.h>	/* define GLUT window and device routines */
#include <math.h>	/* define math library routines */

#define TRUE		1
#define FALSE		0

#define WIDTH		1000	/* window dimensions */
#define HEIGHT		750

#define NCOLORS		15	/* Number of Colors Used	*/

	/* Define the RGB color values to be used */

#define RGBRED		1, 0, 0
#define RGBORANGE	1, 0.5, 0
#define RGBYELLOW	1, 1, 0
#define RGBYELLOWGREEN	0.5, 1, 0
#define RGBGREEN	0, 1, 0
#define RGBGREENCYAN	0, 1, 0.5
#define RGBCYAN		0, 1, 1
#define RGBCYANBLUE	0, 0.5, 1
#define RGBBLUE		0, 0, 1
#define RGBPURPLE	0.5, 0, 1
#define RGBMAGENTA	1, 0, 1
#define RGBVIOLET	1, 0, 0.5
#define RGBBLACK	0, 0, 0
#define RGBGREY		.5,.5,.5
#define RGBWHITE	1, 1, 1

#define RGBDKGREY	0.20, 0.20, 0.20   /* for screen background */

	/* Define Indices for the RGB color values */

#define IDXRED		0
#define IDXORANGE	1
#define IDXYELLOW	2
#define IDXYELLOWGREEN	3
#define IDXGREEN	4
#define IDXGREENCYAN	5
#define IDXCYAN		6
#define IDXCYANBLUE	7
#define IDXBLUE		8
#define IDXPURPLE	9
#define IDXMAGENTA	10
#define IDXVIOLET	11
#define IDXBLACK	12
#define IDXGREY		13
#define IDXWHITE	14
#define IDXDKGREY	15   /* for screen background */

	/* Other Defines	*/

#define NRMLMASK	15   /* index mask for normal drawing */
#define OVLMASK		16   /* index mask for overlay drawing */
#define OVLWHITE	16   /* index of white color for overlay */
#define OVLCLEAR	0    /* index to clear overlay */
#define MAXCOLORS	(OVLMASK * 2)

#define R		0
#define G		1
#define B		2

/******************* Global Variables for Functions *********************/

int firstx, firsty;	/* mouse coordinates on button press */
int lastx, lasty;	/* last mouse drawing coordinates */
int drawing = FALSE;	/* TRUE if button pressed in drawing area */
int colorindex = IDXWHITE; /* initial drawing color is white */

float colorarray[][3] = {{RGBRED}, {RGBORANGE}, {RGBYELLOW}, 
			 {RGBYELLOWGREEN},{RGBGREEN}, {RGBGREENCYAN},
			 {RGBCYAN}, {RGBCYANBLUE}, {RGBBLUE},
			 {RGBPURPLE}, {RGBMAGENTA}, {RGBVIOLET},
			 {RGBBLACK}, {RGBGREY},{RGBWHITE}, {RGBDKGREY}};

/******************* Procedures and Functions *********************/

/*
  Returns true if point (x, y) in the sketch pad area
*/
int insketchpad(int x, int y){

  return(x > 0 && x < WIDTH &&
	 y > 0 && y < HEIGHT);
}

/*
  Draw an outline rectangle with diagonal (x0, y0) to (x1, y1)
*/
void outlinebox(x0, y0, x1, y1){

  glBegin(GL_LINE_LOOP);
    glVertex2i(x0, y0);
    glVertex2i(x0, y1);
    glVertex2i(x1, y1);
    glVertex2i(x1, y0);
  glEnd();
}

/*
  Draw a filled rectangle with diagonal (x0, y0) to (x1, y1)
*/
void fillbox(x0, y0, x1, y1){

  glBegin(GL_POLYGON);
    glVertex2i(x0, y0);
    glVertex2i(x0, y1);
    glVertex2i(x1, y1);
    glVertex2i(x1, y0);
  glEnd();
}

/*
  Draw Overlay Rectangle
*/
void orectangle(int x, int y){

  glIndexi(OVLCLEAR);	/* Erase last Overlay */
  outlinebox(firstx, firsty, lastx, lasty);

  glIndexi(OVLWHITE);	/* Draw new Overlay   */
  outlinebox(firstx, firsty, x, y);

  lastx = x;	/*  save mouse coordinates    */
  lasty = y;
}

/*
  Take drawing action based on new mouse position
*/
void drawMotion(int x, int y){

  y = HEIGHT - y;

  if(drawing && insketchpad(x, y))
    
      orectangle(x, y);	  /*  Update overlay rectangle */
}

/*
  Watch mouse button presses and handle them
*/
void handleButton(int button, int state, int x, int y){

  y = HEIGHT - y;

  if(button != GLUT_LEFT_BUTTON)	/* ignore if not left button	*/
    return;

  if(state == GLUT_DOWN){
    if(insketchpad(x, y)){
      drawing = TRUE;
      firstx = lastx = x;	/* initialize mouse coordinates */
      firsty = lasty = y;

	glIndexMask(OVLMASK);	/* set index mask to overlay	*/
	glClearIndex(OVLCLEAR);	/* set clear color		*/
	glClear(GL_COLOR_BUFFER_BIT);	/* clear overlay 	*/
      }
    }
  else{
    glIndexMask(OVLMASK);	/* set index mask to overlay 	*/	
    glClearIndex(OVLCLEAR);	/* set clear color  		*/
    glClear(GL_COLOR_BUFFER_BIT);  	/* clear overlay 	*/

    glIndexMask(NRMLMASK);	/* restore index mask to normal 	*/
    glIndexi((colorindex++)%15);		/* get new color 	*/
    fillbox(firstx, firsty, lastx, lasty);	/* draw filled box 	*/
    drawing = FALSE;
    }
}

/*
  Draw the sketchpad
*/
void drawSketchpad(){

  glClearIndex(IDXDKGREY);		/* window cleared to dark grey */
  glClear(GL_COLOR_BUFFER_BIT);		/* clear the window */

  glIndexMask(NRMLMASK);	/* set index mask to normal  */	

  glIndexi(colorindex);  	/* set the drawing color index */
}

/*
   Main program to open the main window and register the callbacks
   that draw the sketchpad, service the mouse buttons,
   and service mouse movements.
*/
void main(int argc, char* argv[]){
  
  int i;  

  glutInit(&argc, argv);

  glutInitDisplayMode(GLUT_SINGLE | GLUT_INDEX);
  glutInitWindowSize(WIDTH, HEIGHT);
  glutCreateWindow("Index Overlay Example");

  gluOrtho2D(0, WIDTH, 0, HEIGHT);

  glutDisplayFunc(drawSketchpad);	/* drawing event callback */
  glutMouseFunc(handleButton);		/* mouse button event callback */
  glutMotionFunc(drawMotion);		/* mouse movement callback */

  /* load the color index table with desired colors */
  for(i = 0; i < NCOLORS + 1; i++)
    glutSetColor(i, colorarray[i][R], colorarray[i][G], colorarray[i][B]);

  /* load the rest of the index table with "off-white" */
  for(i = NCOLORS + 1; i < MAXCOLORS; i++)
    glutSetColor(i, .75, .75, .75);

  glutMainLoop();
}