/*
 * GBX driver for fig2dev
 *
 * Output Gerber files using the lowest common denominator.
 *
 * Gerber is a file format for the CAD of PCBs.  This code produces
 * output which (should) conform to the specification for RS-247-X
 * described in the following document.
 *
 * http://members.optusnet.com.au/~eseychell/rs274xrevd_e.pdf
 *
 * I have taken care to make sure that join styles and end caps are
 * honoured in the export to Gerber.  Many FIG primitives cannot be
 * faithfully reproduced in Gerber. For example.
 *
 *   -) Colour - Only black or "default" coloured items are exported.
 *   -) Ellipses - Ignored.
 *   -) Curved splies - Cannot be faithfully reproduced.
 *   -) Hatched or non uniform fills - Not supported.
 *   -) Dashed lines - Not suported.
 *   -) Fancy end caps (arrows etc.) - Not supported
 *   -) Multiple layers - These are flattened to one layer.  Gerber does 
 *      support multiple layers, however there is currently no option 
 *      to preserve these.
 *
 * It should be realised that Gerber is _not_ a well supported
 * standard and various output devices do not honour certain aspects
 * of it.  Good luck!
 * 
 * Author: Edward Grace <edward.grace@gmail.com>
 *
 */

#include "fig2dev.h"
#include "object.h"
#include "../../patchlevel.h"
#include "alloc.h"

#define GBX_DRIVER_VERSION "0.1.1"
#define MAX_APERTURES 989
#define GBX_BUF_SIZE 1024

/* Enumeration for units to use in output.  Inches are natural to FIG. */
enum gbx_units { units_mm, units_inches };

/* Number of leading and trailing digits around the decimal point.*/
int gbx_before = 3;
int gbx_after  = 5;
/* Dimensions to assume for output */
int gbx_dimensions = units_mm;
/* Scale factor to ascribe to the output image. */
float gbx_scale_factor_a = 1;
float gbx_scale_factor_b = 1;
/* Image polarity. 0->positive 1->negative. */
int gbx_image_polarity = 1;
/* Offset in a and b axis */
float gbx_offset_a=0, gbx_offset_b=0;
/* Should we include debug comments in GBX? */
int gbx_debug_comments=1;

/* Warning stack. */
enum warnings { warn=0, warn_square_join, 
		warn_filled_poly_with_line, 
		warn_open_filled_polygon,
		warn_open_filled_arc,
		warn_text_unsupported,
		warn_ellipse_unsupported,
		warn_spline_not_implemented,
		warn_arrow_not_implemented,
		warn_line_colour,
		warn_line_zero_width,
		warn_max };
int warning_counts[warn_max];

/* TODO - These should be defined from FIG, as they may change */
enum pen_colours { p_colour_default = -1, 
		   p_colour_black = 0,
		   p_colour_max };

/* TODO - These should be defined from FIG, as they may change */
enum fill_colours { f_colour_red = 0 };

/* Output a warning regarding a certain type of primative once,
   keeping track of the number of times the warning has been given. */
void warn_once(long int warning_type, char *message) {
  if (warning_counts[warning_type])
    return;

  fprintf(stderr, "Warning:%s\n",message);
  ++warning_counts[warning_type];
}

/* Boolean to state if the plotter exposure is on or not. */
unsigned long int is_exposure=1;

/* Function prototypes, just to keep the compiler quiet. */
void  print_comments(char *string, F_comment *comment, char *string2);

/* Return the length of a vector. */
double length (long int x1, long int y1, long int x2, long int y2) {
  double deltax=(double)(x2-x1), deltay=(double)(y2-y1);
  double l=0;
  if (abs(deltax) > abs(deltay)) {
    l =  abs(deltax) * sqrt(1.0 + (deltay/deltax)*(deltay/deltax));
  } else {
    l =  abs(deltay) * sqrt(1.0 + (deltax/deltay)*(deltax/deltay));
  }
  return l;
}

/* enums describing FIG styles etc. */
enum cap_styles { cap_style_butt=0, cap_style_round, cap_style_square };

/* enums describing FIG fill styles. */
enum fill_styles { fill_style_none=-1 };

long unsigned long int gbx_scale_factor;

/* Fundemental scaling parameters. */
#define INCH2MM  25.4
#define WIDTH_FIG2IN  (1.0/1200.0)
#define WIDTH_FIG2MM  (25.4/1200.0)

#define XY_FIG2IN (1.0/1200.0)
#define XY_FIG2MM (XY_FIG2IN * INCH2MM)

char outbuf[GBX_BUF_SIZE];

void write_end_block(void);
void gengbx_line (F_line *l);

/* Parameter counts.  Used for internal validataion. */
unsigned long int count_begin_param=0;
unsigned long int count_end_param=0;
unsigned long int count_data_block=0;

/* Last code type - keeps track of the type of code last written. */
enum code_types { g_code=0, m_code=1, d_code=2 };
unsigned long int last_code_type=-1;
unsigned long int last_code_value=-1;

/*
 * Begin a parameter. 
 */
void begin_param() { fprintf( tfp, "%%" ); ++count_begin_param; }

/*
 * End a parameter.
 */
void end_param() { fprintf( tfp, "%%\n" ); ++count_end_param; }


/* 
 * Enumerate M codes (misc codes)
 */
unsigned long int total_m_code_count=0;
enum m_codes { program_stop = 0, optional_stop = 1, end_of_program = 2 };
void write_m_code(enum m_codes m) {
  fprintf(tfp, "M%02u",m);
  last_code_type=m_code;
  last_code_value=m;
  write_end_block();
}

/*
 * Check to see if the supplied colour is ok to output.  This is
 * useful for ignoring construction lines. By default only output
 * black lines or lines with colour "default".
 *
 * Need to add a command line option to disable this.
 */
int is_pen_colour_ok(long int colour) {
  switch (colour) {
  case p_colour_black:
  case p_colour_default:
    return 1;
  }
 
  warn_once(warn_line_colour,"By default only objects with line colour of \"default\" or  \"black\" are output.");
  return 0;
}

/* 
 * Enumerate D codes (draft codes) selects apertures and determine if
 * the feature to be drawn should be a line or "flashed".
 */
unsigned long int total_d_code_count=0;
enum d_codes { d_exposure_on = 1, d_exposure_off = 2, 
	       d_flash = 3, d_select_aperture = 10 };

/** Define the maximum aperture index. */
#define MAX_D_CODE 999
#define MAX_APERTURE_INDEX (MAX_D_CODE - d_select_aperture)



/** Keeps count of the number of defined apertures. */
unsigned long int count_apertures = 0;

/** Keeps count of the number of defined simple circular apertures. */
unsigned long int count_circ_aperture = 0;
unsigned long int count_square_aperture = 0;
unsigned long int count_ellipse_aperture = 0;

/** Simple structure to represent simple circular apertures. */
struct ap_circ {
  double dia;
};

/** Simple structure to represent elliptical apertures. */
struct ap_ellipse {
  double w,h;
};

/** Square apertures. */
struct ap_square {
  double width;
};

/** Define a buffer containing all the apertures to be defined. */
struct ap_circ aperture_circ_list[MAX_APERTURE_INDEX];
struct ap_square aperture_square_list[MAX_APERTURE_INDEX];
struct ap_ellipse aperture_ellipse_list[MAX_APERTURE_INDEX];


/** 
  Test two numbers for equality by comparing their string representation.
*/
int is_double_equal(double a, double b) {
  char s_a[80], s_b[80];
  sprintf(s_a,"%f",a);
  sprintf(s_b,"%f",b);
  return strcmp(s_a,s_b) == 0 ? 1 : 0;
}

/** 
    Returns the index of any simple circle if it already exists. 

    -1 if it does not exists.
*/
int test_ap_circ(double outer_dia) {
  long int n=0;
  for (n=0; n<count_circ_aperture; ++n) {
    //    fprintf(stderr, "%f, %f\n", aperture_circ_list[n].dia, outer_dia);
    if ( is_double_equal(aperture_circ_list[n].dia,outer_dia) ) {
      return n;
    }
  }
  return -1;
}


/** 
    Returns the index of an elliptical aperture if it already exists. 

    -1 if it does not exists.
*/
int test_ap_ellipse(double w, double h) {
  long int n=0;
  for (n=0; n<count_ellipse_aperture; ++n) {
    if ( is_double_equal(aperture_ellipse_list[n].w,w) && 
	 is_double_equal(aperture_ellipse_list[n].h,h) ) {
      return n;
    }
  }
  return -1;
}

int test_ap_square(double width) {
  long int n=0;
  for (n=0; n<count_square_aperture; ++n) {
    // fprintf(stderr,"%f, %f\n",aperture_square_list[n].width, width);
     if ( is_double_equal(aperture_square_list[n].width,width) ) {
      return n;
    }
  }
  return -1;
}


/** Returns 1 if the aperture is defined, zero if not defined. */
int is_aperture_defined(unsigned long int index) { 
  return index < count_apertures ? 1 : 0;
}

unsigned long int total_g_code_count = 0 ;
/* Enumerate G (general function) codes. */
enum g_codes { move = 00, line_interp_1x = 01, 
	       circ_interp_clock = 02, circ_interp_anti = 03,
	       ignore_data_block = 04,
	       lin_interp_10x = 10,
	       lin_interp_01x = 11,
	       lin_interp_001x = 12,
	       poly_area_fill_on = 36, poly_area_fill_off = 37,
	       tool_prepare = 54, 
	       dim_inches = 70, dim_mm = 71,
	       circ_interp_disable = 74, circ_interp_enable = 75,
	       abs_meas = 90, rel_meas = 91 };


/*
 * Mark end of data block.  Do this inteligently. 
 *
 * e.g. If the most recent data block is a comment add a new line.
 */
void write_end_block() { 
  fprintf( tfp, "*\n" ); 
  ++count_data_block; 
}


/** Print the G code padded with zeros to produce two characters. 
    
    e.g. G03 */
void write_g_code(enum g_codes g) { 
  fprintf(tfp, "G%02u",g); 
  total_g_code_count++; 
  last_code_type=g_code;
  last_code_value=g;
}


extern long int  pagewidth, pageheight; 

int     vw, vh; 


/** Convert the units from fig to gbx */
double width_fig2gbx(long int f) {
  double conversion_factor = gbx_dimensions == units_mm ? XY_FIG2MM : XY_FIG2IN;
  return (double)(f * mag * conversion_factor );
}


/** Convert position units from fig to gbx */
int x_fig2gbx(long int f) {
  double conversion_factor = gbx_dimensions == units_mm ? XY_FIG2MM : XY_FIG2IN;
  /* FIXIT Scaling by -ve number alters clockwise -> anticlockwise and can screw up arcs. */
  return (int) f * mag * conversion_factor * gbx_scale_factor;
}

/** Convert position units from fig to gbx */
int y_fig2gbx(long int f) {
  double conversion_factor = gbx_dimensions == units_mm ? XY_FIG2MM : XY_FIG2IN;
 long int newheight;
  /* FIXIT - Scaling for y [b] axis, should be reversed. */
  newheight =  (int)f*mag*conversion_factor * gbx_scale_factor;
  return newheight;
}

/** Print a D code padded with zeros to produce two characters.

    e.g. D03 - Flash aperture.

    For D codes of 10 or greater this checks to see if an appropriate
    aperture has been defined and if it is in range.  If not it will
    produce an error and quit.
*/
void write_d_code(enum d_codes d) { 
  if (d < 10) {
    fprintf(tfp, "D%02u", d);
  } else {
    fprintf(tfp, "D%u", d);
  } 
  last_code_type=d_code;
  last_code_value=d;
}

/** Switch off exposure of pen. */
void exposure_off() {
  write_d_code(d_exposure_off);
  is_exposure=0;
}

void exposure_on() {
  write_d_code(d_exposure_on);
  is_exposure=1;
}
  
/** Select an aperture to use for drawing. */
void use_aperture(long int aperture_index) {
  write_g_code(tool_prepare);
  write_d_code(d_select_aperture + aperture_index);
  write_end_block();
}


/** Higher level functions for writing entities like comments,
    aperture declarations etc.
*/
void write_comment(char *c) {
  fprintf(tfp, "G%02i %s*\n",ignore_data_block,c);
}

/* Writes traceing output for the types of object */
void write_trace(char *c) {
  if ( gbx_debug_comments ) 
    write_comment(c);
}

/** Output coordinate information to the file. */
void xy(long int x, long int y) {
  fprintf(tfp, "X%iY%i", x_fig2gbx(x), y_fig2gbx(y));
}

/** Draw from the current point to the final point specified by x, y.
    Switches on the exposure if it is currently off. */
void draw_xy(long int x, long int y) {
  xy(x,y);
  if (!is_exposure)
    exposure_on();
  write_end_block();
}

/** Go from current point to specified point with exposure off. */
void move_xy(long int x, long int y) {
  xy(x,y);
  exposure_off();
  write_end_block();
}

/** Move to a point specified by x,y and flash the given aperture at
    this point. */
void flash_xy(long int x, long int y, int aperture_index ) {
  if (is_exposure)
    exposure_off();
  write_end_block();
  write_g_code(tool_prepare);
  write_d_code(d_select_aperture + aperture_index);
  write_end_block();
  xy(x,y);
  write_d_code(d_flash);
  write_end_block();
}
  

/** Define a filled circular aperture given the diameter.
    
    Returns the corresponding aperture index. 
*/ 
unsigned long int ad_aperture_define_circ(double outer_dia) {
  /* Check to see if the aperture count is zero, if so initialise the array*/
  long int index;
  if (!count_circ_aperture)
    for (index=0; index<MAX_APERTURE_INDEX; ++index)
      aperture_circ_list[index].dia=-1.0;
  
  /* Sanity check on aperture size */
  if (! (outer_dia > 0.0) ) {
    fprintf(stderr,"Error: Something tried to define a circular aperture of zero size.\n");
    exit(1);
  }

  /* First check to see if the aperture is defined. */
  long int ap_index = test_ap_circ(outer_dia);

  /* If the aperture has not been defined, add it. */
  if (ap_index == -1) {
    ap_index = count_apertures;
    fprintf(tfp, "%%ADD%liC,%f%%*\n",d_select_aperture + ap_index, outer_dia );
    aperture_circ_list[ap_index].dia=outer_dia;

    count_circ_aperture++;
    count_apertures++;
  }

  /* Return the index to this aperture. */ 
  return ap_index;
}

/** Define a filled elliptical aperture given the width and height.
    
    Returns the corresponding aperture index. 
*/ 
unsigned long int ad_aperture_define_ellipse(double w, double h) {
  /* Check to see if the aperture count is zero, if so initialise the array*/
  long int index;
  if (!count_ellipse_aperture)
    for (index=0; index<MAX_APERTURE_INDEX; ++index) {
      aperture_ellipse_list[index].w=-1.0;
      aperture_ellipse_list[index].h=-1.0;
    }

  /* Sanity check on aperture size */
  if (! ( w > 0.0 && h > 0.0 ) ) {
    fprintf(stderr,"Error: Something tried to define an elliptical aperture of zero size.\n");
    exit(1);
  }

  /* First check to see if the aperture is defined. */
  long int ap_index = test_ap_ellipse(w,h);

  /* If the aperture has not been defined, add it. */
  if (ap_index == -1) {
    ap_index = count_apertures;
    fprintf(tfp, "%%ADD%liO,%fX%f*%%\n",d_select_aperture + ap_index, w, h);
    aperture_ellipse_list[ap_index].w=w;
    aperture_ellipse_list[ap_index].h=h;

    count_ellipse_aperture++;
    count_apertures++;
  }

  /* Return the index to this aperture. */ 
  return ap_index;
}

/** Define a filled square aperture given the width.
   
    Returns the corresponding aperture index.
*/
unsigned long int ad_aperture_define_square(double width) {
  /* Check to see if the aperture count is zero, if so initialise the array*/
  long int index;
  if (!count_square_aperture)
    for (index=0; index<MAX_APERTURE_INDEX; ++index) {
      aperture_square_list[index].width=-1.0;
    }

  /* Sanity check on aperture size */
  if (! ( width > 0.0 ) ) {
    fprintf(stderr,"Error: Something tried to define a square aperture of zero size.\n");
    exit(1);
  }

   /* First check to see if the aperture is defined. */
  long int ap_index = test_ap_square(width);
  
  /* If the aperture has not been defined, add it. */
  if (ap_index == -1) {
    ap_index = count_apertures; 
    fprintf(tfp, "%%ADD%liR,%fX%f*%%\n",d_select_aperture + ap_index, width, width);
    aperture_square_list[ap_index].width=width;
  
    count_square_aperture++;
    count_apertures++;
  }
  return ap_index;
}


/** Given a pointer to a line this determines from the line what
    aperture to use, circular or rectangular.  If necessary it then
    defines it and returns the aperture index. */
int define_aperture_for_line(F_line *l) {
  long int index;
  double width;
  width = width_fig2gbx(l->thickness);

  /* 
     The prevailing aperture style is set from the join style.
  */
  if (l->join_style == 1) 
    index=ad_aperture_define_circ(width);
  else  {
    index=ad_aperture_define_square(width);
    /* If there are more than two points in a line issue a warning. */
    if (l->points && l->points->next && l->points->next->next && l->points->next->next->next) 
      warn_once(warn_square_join, "Join style of square does not translate well to intermediate points in Gerber format.");
  }
  return index;
}

/** Given a pointer to a line this determines from the line what
    aperture to use, circular or rectangular for the end caps..  If
    necessary it then defines it and returns the aperture index. */
int define_aperture_for_line_end(F_line *l) {
  long int index;
  double width;
  width = width_fig2gbx(l->thickness);

  /* 
     The prevailing aperture style is set from the cap style.
  */
  if (l->cap_style == 1) 
    index=ad_aperture_define_circ(width);
  else  {
    index=ad_aperture_define_square(width); 
  }
  return index;
}

int define_aperture_for_arc(F_arc *a) {
  long int index;
  double width;
  width = width_fig2gbx(a->thickness);
  if (a->cap_style  == 1)
    index=ad_aperture_define_circ(width);
  else 
    index=ad_aperture_define_square(width);
  return index;
}


char   *cctype[] = { "none", "black", "white" };

/* arrowhead arrays */
Point   points[50];
int     npoints;
int     arrowx1, arrowy1;	/* first point of object */
int     arrowx2, arrowy2;	/* second point of object */

static F_point *p;

/** Used to generate sequence numbers. */
unsigned long int sequence_number=0;

/** Total count of data blocks that have been written. */
unsigned long int block_total_count=0;

/** Current count of the number of blocks written on a line.  Used for
    formatting purposes. */
unsigned long int block_horizontal_count=0;

/** Maximum number of data blocks to write horizontally. */
unsigned long int max_block_horizontal_count=10;

/*
  Process options for producing the Gerber file.
*/
void gengbx_option(opt, optarg)
     char opt;
     char *optarg;
{
  
  switch (opt) {
    /* Ignore Language, font, fontsize options.*/
  case 'h':
  case 'V': 
  case 'F':
  case 'G':	
  case 'L':
  case 's':
  case 'm':
  case 'j':
  case 'D':	  
  case '?':
    break;
  case 'd':
    if (strcmp(optarg,"mm") == 0 )
      gbx_dimensions = units_mm;
    else if (strcmp(optarg,"in") == 0 )
      gbx_dimensions = units_inches;
    else
      fprintf(stderr,"Dimensions should be given in 'mm' for millimeters or 'in' for inches respectively\n");
    break;
  case 'p':
    /* Image polarity. [+,-] */
    if (strcmp(optarg,"pos") == 0 || strcmp(optarg,"+") == 0 ) 
      gbx_image_polarity = 0;
    else if (strcmp(optarg,"neg") == 0 || strcmp(optarg,"-") == 0) 
      gbx_image_polarity = 1;
    else 
      fprintf(stderr,"Polarity option should be [+,pos] for positive images (marks add material making it opaque) or [-,neg] for negative images (marks remove material, making it transparent)\n");
    break;
  case 'g':
    /* Scaling and offset, form -s <double>x<double>+<double>+<double> */
    if ( sscanf(optarg,"%fx%f+%f+%f",&gbx_scale_factor_a,&gbx_scale_factor_b,&gbx_offset_a, &gbx_offset_b) == 0)
      fprintf(stderr,"Error in scaling format, expect <double>x<double>+<double>+<double> for X and Y scale and x, y offset respectively.\n");
    break;
  case 'f':
    /* Numerical format, ofrm -f <integer>.<integer> */
    if ( sscanf(optarg,"%u.%u",&gbx_before, &gbx_after) == 0 ) 
      fprintf(stderr,"Error in numeric format, expect form  <unsigned int>.<unsigned int> for degree of precision.\n");
    if (gbx_before > 4) 
      fprintf(stderr,"Warning: Having more than 4 digits before the decimal place is unusual\n");
    if (gbx_after > 5)
      fprintf(stderr,"Warning: Having more than 5 digits after the decimal place is unusual\n");
    if (gbx_before + gbx_after  > 9)
      fprintf(stderr,"Warning: Having more than nine significant figures is usually unrealistic\n");
    break;
  case 'i':
    /* Include debug comments? */
    if ( strcmp(optarg,"off") == 0) 
      gbx_debug_comments = 0;
    else if ( strcmp(optarg,"on") == 0)
      gbx_debug_comments = 1;
    else
      fprintf(stderr,"Error: Debug comments option should be 'on' or 'off'\n");
    break;
  default:
    put_msg(Err_badarg, opt, "gbx");
    exit(1);
  }
}

void
gengbx_start (objects)
     F_compound *objects;
{
  //struct paperdef *pd;      
  time_t  when; 
  char    stime[80]; 
  /*     long int     i; */

  gbx_scale_factor=pow(10,gbx_after);

  write_comment("Gerber RS-274x file"); 

  sprintf(outbuf, "Creator: %s",prog);   write_comment(outbuf);
  sprintf(outbuf, "Version: %s", VERSION); write_comment(outbuf);
  sprintf(outbuf, "Patchlevel: %s", PATCHLEVEL); write_comment(outbuf);
  sprintf(outbuf, "Driver version: %s", GBX_DRIVER_VERSION); write_comment(outbuf);
  write_comment("Author: Edward Grace <edward.grace@gmail.com>");
  
  (void) time (&when);
  strcpy (stime, ctime (&when));
  /* remove trailing newline from date/time */
  stime[strlen (stime) - 1] = '\0';

  sprintf(outbuf, "Creation date: %s", stime); write_comment(outbuf);
  
  switch (gbx_dimensions) {
  case units_mm:
    fprintf(tfp,"%%MOMM*%%\n");
    break;
  case units_inches:
    fprintf(tfp,"%%MOIN*%%\n");
    break;
  default:
    fprintf(stderr, "Error: Do not know about the unit choice. %i internal error.\n",gbx_dimensions);
    exit(1);
  }

  fprintf(tfp,"%%OFA%fB%f*%%\n",gbx_offset_a, gbx_offset_b);
  fprintf(tfp, "%%FSLAX%i%iY%i%i*%%\n", gbx_before,gbx_after,gbx_before,gbx_after);
  fprintf(tfp, "%%SFA%fB%f%%\n",gbx_scale_factor_a,gbx_scale_factor_b);
  if (gbx_image_polarity) 
    fprintf(tfp,"%%IPNEG*%%\n");
  else
    fprintf(tfp,"%%IPPOS*%%\n");
  fprintf(tfp, "%%LPD*%%\n");

  write_comment("The following is an aperture definition of width pi/10.  It should never be used.");
  ad_aperture_define_square(0.314159);
}

/** Output end of file marker. */
int gengbx_end () {
  write_m_code(end_of_program);
  return 0;
}

/** Intenal math roughtine.  Determine the change in x and y required
    to move from point 1 to point 2 by a distance l joining the
    lines. */
void get_dx_dy(long int x1, long int y1, long int x2, long int y2, long int dist, double *dx, double *dy) {
  double l = length(x1, y1, x2, y2);
  *dx=(double)(dist*(x2-x1)/l);
  *dy=(double)(dist*(y2-y1)/l);
}

/** Insert points in a polyline after the given point, returning a
    pointer to the added points. This is used to manage different join
    styles in Gerber.*/
F_point * insert_after_point(F_point *p) {
  F_point * pnew;
  Point_malloc(pnew);
  pnew->x = p->x;
  pnew->y = p->y;
  pnew->next = p->next;
  p->next=pnew;
  return pnew;
}

void gengbx_line (F_line *l) {
  /* Always check. If the colour is not black or "default" then bail
     out with a warning. */
  if (! is_pen_colour_ok(l->pen_color) ) return;
		    
  /* If line thickness is less than or equal to zero, warn and don't output. */
  if ( ( ! l->thickness > 0.0 ) && l->fill_style == fill_style_none ) {
    warn_once(warn_line_zero_width,"Unfilled line of zero width, ignoring.");
    return;
  }


  double dx,dy;

  /* Used to compare the start and end points of polygons. */
  long int x1=0,x2=0,y1=0,y2=0;

  /*
    First check to see if the line has all points at the same place.
    If they are all at the same place then this "line" should be
    interpreted as a flashed aperture of the appropriate shape. 
  */
  long int is_same_place = 1;
  p = l->points; x1=p->x; y1=p->y; 
  for (p = p->next; p; p = p->next) {
    is_same_place = p->x == x1 && p->y == y1 ? 1 : 0;
    if (!is_same_place) 
      break;
    x1=p->x; y1=p->y;
  }
  if (is_same_place) {
    flash_xy(x1, y1, define_aperture_for_line(l));
    return;
  }

  /* Now determine if its a filled polygon. */
  if (l->fill_style == fill_style_none) {
    write_trace("## START:POLYGON:OPEN");
  } else {
    write_trace("## START:POLYGON:CLOSED");
  }

  
   /* Now find the penultimate point of the line by traversing the
     list, also store the total number of points in n_points. */
  long int n_points=0;
  long int n_points_original=0;
  F_point *p_penultimate = l->points;
  for (p = l->points; p->next; p = p->next, ++n_points)
    p_penultimate = p;
  ++n_points;
  n_points_original=n_points;
 
 /** The following evaluates to unity if the line has square ends and
     circular join style, AND is long enough to actually mean
     something. */
  long int circsquare=0;

  if (l->join_style == 1 && ((l->cap_style == cap_style_butt )
			     || l->cap_style == cap_style_square))  {
    if (n_points > 2) 
      circsquare=1;
    else 
      l->join_style = 0;
  }

  /* Open polygon. */
  if (l->fill_style == fill_style_none) {
    if (l->type != T_BOX && l->type != T_ARC_BOX && l->type !=  T_POLYGON ) {

      /* For a butt end cap move the first and last points half the
	 thickness of the line forward and backward respectively.

	 *** Preprocess Line ****

      */
      if ( l->cap_style == cap_style_butt && l->points->next ) {

	/* Go to start of line. */
	p = l->points; 
	x1=p->x; y1=p->y;
	p=p->next; x2=p->x; y2=p->y;

	/* Shift the beginning point along by half the line thickness. */
	get_dx_dy(x1, y1, x2, y2, l->thickness/2, &dx, &dy);
	p = l->points;
	p->x += round(dx); p->y += round(dy);
	
	/* Set p to the penultimate point. */
	p = p_penultimate;
	x1=p->x; y1=p->y; p=p->next;
	x2=p->x; y2=p->y; 
	
	/* Shift the end point back by half a line thickness. */

	//	fprintf(stderr,"***** HERE %li, %li, %li ****\n",l->points,l->points->next,p_penultimate);
	get_dx_dy(x1, y1, x2, y2, l->thickness/2, &dx, &dy);
	p->x -= round(dx); p->y -= round(dy);
      }


      F_point *p2, *pA, *pB;
      if ( circsquare ) {
	if (n_points_original >= 3) {
	  /** Circular join style square end style. 
	      
	      Need to move second and third points (if they exist) so
	      that they are out the way */
	  p = l->points;
	  p2 = p->next;
	  
	  pA=insert_after_point(p2); n_points++;
	  pB=insert_after_point(p2); n_points++;
	  
	  /* Will move the second+3rd point back to make way for the circular join. */
	  p = l->points;
	  p2 = p->next;
	  x1=p->x; y1=p->y;
	  x2=p2->x; y2=p2->y;
	  get_dx_dy(x1, y1, x2, y2, l->thickness/2, &dx, &dy);
	  p2->x -= round(dx); p2->y -= round(dy);
	  

	  if (n_points_original == 3) {
	    /* If there are just three original points we want to move
	       the (now) 4th point forward. */
	    p = pA;
	    p2 = p->next;	    
	  } else {
	    /* Similarly for the new point after the original second point. */
	    p = pB->next;
	    p2 = p->next;
	  }
	  x1=p->x; y1=p->y;
	  x2=p2->x; y2=p2->y;
	  get_dx_dy(x1, y1, x2, y2, l->thickness/2, &dx, &dy);
	  p->x += round(dx); p->y += round(dy);
	} 

	if ( n_points_original > 3 ) {
	  
	  /* Insert a new penultimate point */
	  pA = insert_after_point(p_penultimate); n_points++;
	  
	  /* Move the new penultimate point forward slightly. */
	  p = pA;
	  p2 = p->next;
	  x1=p->x; y1=p->y;
	  x2=p2->x; y2=p2->y;
	  get_dx_dy(x1, y1, x2, y2, l->thickness/2, &dx, &dy);
	  p->x += round(dx); p->y += round(dy);
	}
      }
    } 
    
    
    /* If we have square ends with round joins we need to swap over to
       a circular aperture for the main part of the line. 

       Draw the line.

    */
    if (circsquare) {
      if (n_points_original == 3) {
	/* The line has been modified to have 5 points, the first and
	   last pair are line segments to draw with square cross
	   section.  The 3rd point is an aperture to flash. */
	p = l->points;
	
	use_aperture(define_aperture_for_line_end(l));

	/* Move to start point */
	move_xy(p->x, p->y);

	/* Draw first segment with end cap style.*/
	p = p->next;
	draw_xy(p->x, p->y);
	
	/* Now flash the aperture at the corner. */
	p = p->next;
	flash_xy(p->x, p->y, define_aperture_for_line(l));
	
	/* Now draw the final line segment. */
	p = p->next;
	use_aperture(define_aperture_for_line_end(l));
	move_xy(p->x, p->y);
	
	p=p->next;
	draw_xy(p->x, p->y);
      } else if (n_points_original > 3) {
	/* The line has been modified to add end sections to allow us to
	   draw the end as a square and the joining parts as circular
	   apertures. */
	
	
	/* Start to draw the line.  First move to the start point. */
	p = l->points;
	
	/* Set the aperture to the end cap aperture. */
	use_aperture(define_aperture_for_line_end(l));
	
	/* Move to start point of line */
	move_xy(p->x, p->y);
	
	/* Draw the first segment with the end cap style. */
	p = p->next;
	draw_xy(p->x, p->y);
	
	/* Set the aperture to the join style */
	use_aperture(define_aperture_for_line(l));
	
	/* Move to end of square line */
	move_xy(p->x,p->y);
	p = p->next;
	/* Draw first part of circular line cross section.*/
	draw_xy(p->x, p->y);
	p = p->next;
	draw_xy(p->x, p->y);
	move_xy(p->x,p->y);
	
	/* Draw the remainder - using the join style. */
	for (; p->next->next ; p = p->next)
	  draw_xy(p->x, p->y);
	
	/* Add end section of line. */
	use_aperture(define_aperture_for_line_end(l));
	move_xy(p->x,p->y);
	p = p->next;
	draw_xy(p->x,p->y);
      }
    }  else {
      /* All other lines get drawn like this. */
      p = l->points;
      use_aperture(define_aperture_for_line(l));
      move_xy(p->x,p->y);
      p=p->next;
      for (; p; p=p->next)
	  draw_xy(p->x,p->y);
    }
    write_trace("## END:POLYGON:OPEN");
  } else {
    /* Ok.  Hold on to your hats.  If the polygon line thickness is non zero and it's a filled polygon
       issue a warning, then set the polygon fill style to -1 (no fill) and call this function again.

       That will result in the other branch of code being called.
       i.e. A line will be generated with the same coordinates as the
       polygon outlining this region.

       Recursive behaviour.  See Recursive behaviour.
    */
    if (l->thickness > 0.0 ) {
      warn_once(warn_filled_poly_with_line,"You have specified a filled polygon with a finite edge thickness.  Check this is what you want");
    

      l->fill_style = fill_style_none;
      /* Call myself, generating an outline around the polygon of the appropriate line width */
      gengbx_line(l);
    }

    p = l->points;
    x1 = p->x; y1 = p->y;
    move_xy(p->x, p->y);
    write_g_code(poly_area_fill_on); write_end_block();
    for  (p = l->points, p = p->next; p; p = p->next) {
      draw_xy(p->x, p->y);
      x2 = p->x; y2 = p->y;
    }
    write_g_code(poly_area_fill_off); write_end_block();
    
    /* Finish with an explicit exposure off */
    exposure_off(); 
    
    /* The line surrounding the polygon is not closed.  Can lead to
       misrepresentation errors. */
    if (x1 != x2 || y1 != y2 ) 
      warn_once(warn_open_filled_polygon,"A filled polygon is not closed.  This can appear different in the Gerber file.");
    write_trace("## END:POLYGON:FILLED");
  }
  if (l->for_arrow || l->back_arrow ) 
    warn_once(warn_arrow_not_implemented,"Arrows on lines are not yet implemented.");

}

void gengbx_spline (F_spline *s) {
  warn_once(warn_spline_not_implemented,"Splines are not directly implemented.");
}

void
gengbx_arc (F_arc *a) {
  /* Always check. If the colour is not black or "default" then bail
     out with a warning. */
  if (! is_pen_colour_ok(a->pen_color) )  return;
  
  
  /* If line thickness is less than or equal to zero, warn and don't output. */
  if ( (! a->thickness > 0.0 ) && a->fill_style == fill_style_none ) {
    warn_once(warn_line_zero_width,"Unfilled arc of zero width, ignoring.");
    return;
  }
  
  
  if (a->fill_style == fill_style_none) {
    /** We want to draw an unfilled arc. */
    write_trace("## START:ARC:OPEN");
  } else {
    write_trace("## START:ARC:FILLED");
  }
  

  if (a->fill_style == fill_style_none) 
    use_aperture(define_aperture_for_arc(a));
  
  
  move_xy(a->point[0].x, a->point[0].y);
  write_g_code(circ_interp_enable);  write_end_block();
  

  /* If this is to be filled switch on fill */
  if (a->fill_style != fill_style_none) {
    write_g_code(poly_area_fill_on);
    write_end_block();
  }

  /* Need to interpret clockwise and anticlockwise relative to the applied x & y axis scaling */
  long int clockwise = 1;
  /* We now need to determine if this is clockwise or anticlockwise.*/
  if (a->direction == clockwise ) 
    write_g_code(circ_interp_clock);
  else
    write_g_code(circ_interp_anti);
  write_end_block();
     
  fprintf(tfp,"X%iY%iI%iJ%iD01*\n", x_fig2gbx(a->point[2].x), y_fig2gbx(a->point[2].y),
	  x_fig2gbx(a->center.x-a->point[0].x), y_fig2gbx(a->center.y-a->point[0].y)); 

  if (a->fill_style != fill_style_none) { 
    write_g_code(poly_area_fill_off);
    write_end_block();
  }
  write_g_code(circ_interp_disable); write_end_block();
  write_g_code(line_interp_1x); write_end_block();
  exposure_off();
    
  /* If the line has thickness and is filled switch off fill, and call myself to draw the line arc. */
  if (a->thickness > 0  && a->fill_style != fill_style_none) {
    write_trace("## START:ARC:OUTLINE:CURVE");
    a->fill_style = fill_style_none;
    gengbx_arc(a);
    
    /* Issue a warning. We are about to add a border. */
    warn_once(warn_open_filled_arc,"Polygon fill on an arc with finite line thickness.  Check this is what you want.");
    
    /* Draw a line from start to end point. */
    /*use_aperture(define_aperture_for_arc(a));*/
    write_trace("## START:ARC:OUTLINE:LINE");
    
    move_xy(a->point[0].x,a->point[0].y);
    draw_xy(a->point[2].x,a->point[2].y);
    write_trace("## END:ARC:OUTLINE:LINE");
    write_trace("## END:ARC:OUTLINE:CURVE");
  }


  if (a->fill_style == fill_style_none) {
    /** We want to draw an unfilled arc. */
    write_trace("## END:ARC:OPEN");
  } else {
    write_trace("## END:ARC:FILLED");
  }
  

}

void
gengbx_ellipse (F_ellipse *e) {
  if (e->type == T_CIRCLE_BY_RAD || e->type == T_CIRCLE_BY_DIA) { 
    /* Always check. If the colour is not black or "default" then bail
       out with a warning. */
    if (! is_pen_colour_ok(e->pen_color) )  return;

    write_trace("## START:CIRCLE");
    F_arc *a;

    if (NULL == (Arc_malloc(a))) {
      put_msg(Err_mem);
      exit (2);
    }
    a->pen = e->pen;
    a->fill_style = e->fill_style;
    a->for_arrow = NULL;
    a->back_arrow = NULL;
    a->next = NULL;

    /* FIXIT - Warning the /sqrt(2.0) incurrs potential rounding
       errors.  Find a better way to write a circle in Gerber. */
    a->point[0].x = e->center.x + e->radiuses.x/sqrt(2.0);
    a->point[0].y = e->center.y + e->radiuses.y/sqrt(2.0);
    a->point[2].x = e->center.x + e->radiuses.x/sqrt(2.0);
    a->point[2].y = e->center.y + e->radiuses.y/sqrt(2.0);
    a->point[1].x = e->center.x - e->radiuses.x/sqrt(2.0);
    a->point[1].x = e->center.y - e->radiuses.y/sqrt(2.0);
    a->center.x = e->center.x;
    a->center.y = e->center.y;
    a->thickness = e->thickness;
    gengbx_arc(a);
  } else 
    warn_once(warn_ellipse_unsupported,"Ellipse output is currently unsupported.");
  /** To implement the ellipse consider it described parametrically.
      We want to represent the curve as a set of lines such that the
      angle between lines is smaller than a predescribed limit.  This
      requrires knowing the curvature at each point. */
   write_trace( "## END:CIRCLE");
}

void gengbx_text (F_text *t) {
  warn_once(warn_text_unsupported,"Text output is currently unsupported.");
  /* Messy!  Done with a LUT for 0-9 A-Z a-z . - _ / 

     Or, can I translate the PS Type 1 fonts in to polylines? 

     Alternatively use some sort of external program like autotrace as an intermediate stage.

  */
}

/* driver defs */
struct driver dev_gbx = {
  gengbx_option,
  gengbx_start,
  gendev_null,
  gengbx_arc,
  gengbx_ellipse,
  gengbx_line,
  gengbx_spline,
  gengbx_text,
  gengbx_end,
  INCLUDE_TEXT
};