#include "pan.h"
#include "../../util/check_error.h"
#include "../../view/state0.h"
#include <GL/glut.h>

#define S state0

void
pan (int x1, int y1, int x2, int y2)
{
  int dx = x1 - x2;
  int dy = y1 - x2;
  
  if (dx == 0 && dy == 0)
    return;
  
  /*
   * 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.pan.trans[0] += end_position[0] - start_position[0];
  S.pan.trans[1] -= end_position[1] - start_position[1];
  
  glutPostRedisplay ();
  
  return;
}