#include "zoom.h"
#include "../callbacks/reshape.h"
#include "../../util/check_error.h"
#include "../../view/exp004state0.h"
#include <GL/glut.h>
#include <math.h>

/*
 * A simple alias to make the code more readable.
 */
#define S exp004state0

void
zoom (int x1, int y1, int x2, int y2)
{
  /*
   * Convert the selection boundary from window coordinates to
   * world coordinates.
   */
  glMatrixMode (GL_MODELVIEW);
  glLoadIdentity ();
  GLdouble model[16];
  glGetDoublev (GL_MODELVIEW_MATRIX, model);
  GLdouble projection[16];
  glGetDoublev (GL_PROJECTION_MATRIX, projection);
  GLint viewport[4];
  glGetIntegerv (GL_VIEWPORT, viewport);

  check_error (__FILE__, __LINE__);
  
  GLdouble start_position[3];
  gluUnProject (x1,
		y1,
		0,
		model,
		projection,
		viewport,
		&start_position[0],
		&start_position[1], &start_position[2]);
  
  check_error (__FILE__, __LINE__);
  
  GLdouble end_position[3];
  gluUnProject (x2,
		y2,
		0,
		model,
		projection,
		viewport,
		&end_position[0], &end_position[1], &end_position[2]);
  
  check_error (__FILE__, __LINE__);
  
  S.zoom.active = true;
  S.zoom.coords[0] = fmin (start_position[0], end_position[0]);
  S.zoom.coords[1] = fmax (start_position[0], end_position[0]);
  S.zoom.coords[2] = fmin (start_position[1], end_position[1]);
  S.zoom.coords[3] = fmax (start_position[1], end_position[1]);
  
  reshape (S.viewport.w, S.viewport.h);
  
  glutPostRedisplay ();
  
  return;
}