Now resets arrow sizes for illegal arrows.

[dia.git] / lib / arrows.c

/* Dia -- an diagram creation/manipulation program
 * Copyright (C) 1998 Alexander Larsson
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include <config.h>

#include <stdio.h>
#include <string.h>
#include <glib.h>
#include <math.h>
#include "message.h"

#ifdef G_OS_WIN32
#include <float.h>
#define finite(d) _finite(d)
#endif

#ifdef __EMX__
#define finite(d) isfinite(d)
#endif

#include "arrows.h"
#include "diarenderer.h"
#include "intl.h"

struct menudesc arrow_types[] =
  {{N_("None"),ARROW_NONE},
   {N_("Lines"),ARROW_LINES},
   {N_("Hollow Triangle"),ARROW_HOLLOW_TRIANGLE},
   {N_("Filled Triangle"),ARROW_FILLED_TRIANGLE},
   {N_("Unfilled Triangle"),ARROW_UNFILLED_TRIANGLE},
   {N_("Hollow Diamond"),ARROW_HOLLOW_DIAMOND},
   {N_("Filled Diamond"),ARROW_FILLED_DIAMOND},
   {N_("Half Diamond"), ARROW_HALF_DIAMOND},
   {N_("Half Head"),ARROW_HALF_HEAD},
   {N_("Slashed Cross"),ARROW_SLASHED_CROSS},
   {N_("Filled Ellipse"),ARROW_FILLED_ELLIPSE},
   {N_("Hollow Ellipse"),ARROW_HOLLOW_ELLIPSE},
   {N_("Filled Dot"),ARROW_FILLED_DOT},
   {N_("Dimension Origin"),ARROW_DIMENSION_ORIGIN},
   {N_("Blanked Dot"),ARROW_BLANKED_DOT},
   {N_("Double Hollow Triangle"),ARROW_DOUBLE_HOLLOW_TRIANGLE},
   {N_("Double Filled Triangle"),ARROW_DOUBLE_FILLED_TRIANGLE},
   {N_("Filled Dot and Triangle"), ARROW_FILLED_DOT_N_TRIANGLE},
   {N_("Filled Box"),ARROW_FILLED_BOX},
   {N_("Blanked Box"),ARROW_BLANKED_BOX},
   {N_("Slashed"),ARROW_SLASH_ARROW},
   {N_("Integral Symbol"),ARROW_INTEGRAL_SYMBOL},
   {N_("Crow Foot"),ARROW_CROW_FOOT},
   {N_("Cross"),ARROW_CROSS},
   {N_("1-or-many"),ARROW_ONE_OR_MANY},
   {N_("0-or-many"),ARROW_NONE_OR_MANY},
   {N_("1-or-0"),ARROW_ONE_OR_NONE},
   {N_("1 exactly"),ARROW_ONE_EXACTLY},
   {N_("Filled Concave"),ARROW_FILLED_CONCAVE},
   {N_("Blanked Concave"),ARROW_BLANKED_CONCAVE},
   {N_("Round"), ARROW_ROUNDED},
   {N_("Open Round"), ARROW_OPEN_ROUNDED},
   {N_("Backslash"),ARROW_BACKSLASH},
   {N_("Infinite Line"),ARROW_THREE_DOTS},
   {NULL,0}};

/**** prototypes ****/
static void 
draw_empty_ellipse(DiaRenderer *renderer, Point *to, Point *from,
                  real length, real width, real linewidth,
                   Color *fg_color);
static void 
calculate_double_arrow(Point *second_to, Point *second_from, 
                       Point *to, Point *from, real length);

static void 
draw_crow_foot(DiaRenderer *renderer, Point *to, Point *from,
               real length, real width, real linewidth,
               Color *fg_color,Color *bg_color);
static void
calculate_diamond(Point *poly/*[4]*/, Point *to, Point *from,
                  real length, real width);

/** The function calculate_arrow_point adjusts the placement of the line and
 * the arrow, so that the arrow doesn't overshoot the connectionpoint and the
 * line doesn't stick out the other end of the arrow. 
 * @param arrow An arrow to calculate adjustments for.  The arrow type
 *              determins what adjustments are done..
 * @param to Where the arrow points to (e.g. connection point)
 * @param from Where the arrow points from (e.g. bezier control line end)
 * @param move_arrow A place to return the new end point of the arrow head
 *                   (i.e. where 'to' should be to render the arrow head well)
 * @param move_line A place to return the new end point of the line (i.e.
 *                  where 'to' should be to render the connecting line without
 *                  leaving bits of its linewidth outside the arrow).
 * @param linewidth The linewidth used for drawing both arrow and line.
 */
void
calculate_arrow_point(const Arrow *arrow, const Point *to, const Point *from,
                      Point *move_arrow, Point *move_line,
                      real linewidth)
{
  real add_len;
  real angle;
  Point tmp;

  /* Otherwise line is drawn through arrow
   * head for some hollow arrow heads
   * */
  if (linewidth == 0.0)
    linewidth = 0.0001;

  /* First, we move the arrow head backwards.
   * This in most cases just accounts for the linewidth of the arrow.
   * In pointy arrows, this means we must look at the angle of the
   * arrowhead.
   * */
  switch (arrow->type) {
  case ARROW_LINES:
  case ARROW_HOLLOW_TRIANGLE:
  case ARROW_UNFILLED_TRIANGLE:
  case ARROW_FILLED_CONCAVE:
  case ARROW_BLANKED_CONCAVE:
  case ARROW_DOUBLE_HOLLOW_TRIANGLE:
    if (arrow->width < 0.0000001) return;
    angle = atan(arrow->length/(arrow->width/2));
    if (angle < 75*2*G_PI/360.0) {
      add_len = .5*linewidth/cos(angle);
    } else {
      add_len = 0;
    }

    *move_arrow = *to;
    point_sub(move_arrow, from);
    point_normalize(move_arrow);    
    point_scale(move_arrow, add_len);
    break;
  case ARROW_HALF_HEAD:
    if (arrow->width < 0.0000001) return;
    angle = atan(arrow->length/(arrow->width/2));
    if (angle < 60*2*G_PI/360.0) {
      add_len = linewidth/cos(angle);
    } else {
      add_len = 0;
    }

    *move_arrow = *to;
    point_sub(move_arrow, from);
    point_normalize(move_arrow);    
    point_scale(move_arrow, add_len);
    break;
  case ARROW_FILLED_TRIANGLE:
  case ARROW_HOLLOW_ELLIPSE:
  case ARROW_ROUNDED:
  case ARROW_DIMENSION_ORIGIN:
  case ARROW_BLANKED_DOT:
  case ARROW_BLANKED_BOX:
    add_len = .5*linewidth;

    *move_arrow = *to;
    point_sub(move_arrow, from);
    point_normalize(move_arrow);
    point_scale(move_arrow, add_len);
    break;
  case ARROW_ONE_EXACTLY:
  case ARROW_ONE_OR_NONE:
  case ARROW_ONE_OR_MANY:
  case ARROW_NONE_OR_MANY:
  default:
    move_arrow->x = 0.0;
    move_arrow->y = 0.0;
    break;
  }

  /* Now move the line to be behind the arrowhead. */
  switch (arrow->type) {
  case ARROW_LINES:
  case ARROW_HALF_HEAD:
    *move_line = *move_arrow;
    point_scale(move_line, 2.0);
    return;
  case ARROW_HOLLOW_TRIANGLE:
  case ARROW_UNFILLED_TRIANGLE:
  case ARROW_FILLED_TRIANGLE:
  case ARROW_FILLED_ELLIPSE:
  case ARROW_HOLLOW_ELLIPSE:
  case ARROW_ROUNDED:
    *move_line = *move_arrow;
    point_normalize(move_line);
    point_scale(move_line, arrow->length);
    point_add(move_line, move_arrow);
    return;
  case ARROW_HALF_DIAMOND:
  case ARROW_OPEN_ROUNDED:
    /* These don't move the arrow, so *move_arrow can't be used. */
    *move_line = *to;
    point_sub(move_line, from);
    point_normalize(move_line);
    point_scale(move_line, arrow->length);
    point_add(move_line, move_arrow);
    return;
  case ARROW_HOLLOW_DIAMOND:
  case ARROW_FILLED_DIAMOND:
    /* Make move_line be a unit vector in direction of line */
    *move_line = *to;
    point_sub(move_line, from);
    point_normalize(move_line);

    /* Set the length to arrow_length - \/2*linewidth */
    tmp = *move_line;
    point_scale(move_line, arrow->length);
    point_scale(&tmp, G_SQRT2*linewidth);
    point_sub(move_line, &tmp);
    return;
  case ARROW_DIMENSION_ORIGIN:
  case ARROW_BLANKED_DOT:
  case ARROW_BLANKED_BOX:
    *move_line = *move_arrow;
    point_normalize(move_line);
    point_scale(move_line, .5*arrow->length);
    return;
  case ARROW_FILLED_DOT:
  case ARROW_FILLED_BOX:
    *move_line = *to;
    point_sub(move_line, from);
    point_normalize(move_line);
    point_scale(move_line, .5*arrow->length);
    return;
  case ARROW_FILLED_CONCAVE:
  case ARROW_BLANKED_CONCAVE:
    *move_line = *move_arrow;
    point_normalize(move_line);
    point_scale(move_line, .75*arrow->length);
    point_add(move_line, move_arrow);
    return;
  case ARROW_DOUBLE_HOLLOW_TRIANGLE:
    *move_line = *move_arrow;
    point_normalize(move_line);
    tmp = *move_line;
    point_scale(move_line, 2.0*arrow->length);
    point_add(move_line, move_arrow);
    point_scale(&tmp, linewidth);
    point_add(move_line, &tmp);
    return;
  case ARROW_DOUBLE_FILLED_TRIANGLE:
    *move_line = *to;
    point_sub(move_line, from);
    point_normalize(move_line);
    point_scale(move_line, 2*arrow->length);
    return;
  case ARROW_FILLED_DOT_N_TRIANGLE:
    *move_line = *to;
    point_sub(move_line, from);
    point_normalize(move_line);
    point_scale(move_line, arrow->length + arrow->width);
    return;
  case ARROW_THREE_DOTS:
    *move_line = *to;
    point_sub(move_line, from);
    add_len = point_len(move_line);
    point_normalize(move_line);
    if (add_len > 4*arrow->length)
      point_scale(move_line, 2*arrow->length);
    else
      point_scale(move_line, arrow->length);
    return;
  case ARROW_SLASH_ARROW:
  case ARROW_INTEGRAL_SYMBOL:
    *move_line = *to;
    point_sub(move_line, from);
    add_len = point_len(move_line);
    point_normalize(move_line);
    point_scale(move_line, arrow->length / 2);
    return;
  case ARROW_ONE_EXACTLY:
  case ARROW_ONE_OR_NONE:
  case ARROW_ONE_OR_MANY:
  case ARROW_NONE_OR_MANY:
  default: 
    move_arrow->x = 0.0;
    move_arrow->y = 0.0;
    move_line->x = 0.0;
    move_line->y = 0.0;
    return;
  }
}

/** Calculate the corners of a normal arrow.
 * @param poly A three-element array in which to return the three points
 *             involved in making a simple arrow: poly[0] is the right-
 *             hand point, poly[1] is the tip, and poly[2] is the left-hand
 *             point.
 * @param to Where the arrow is pointing to
 * @param from Where the arrow is pointing from (e.g. the end of the stem)
 * @param length How long the arrowhead should be.
 * @param width How wide the arrowhead should be.
 */
static void
calculate_arrow(Point *poly, Point *to, Point *from,
                real length, real width)
{
  Point delta;
  Point orth_delta;
  real len;
  
  delta = *to;
  point_sub(&delta, from);
  len = point_len(&delta);
  if (len <= 0.0001) {
    delta.x=1.0;
    delta.y=0.0;
  } else {
    delta.x/=len;
    delta.y/=len;
  }

  orth_delta.x = delta.y;
  orth_delta.y = -delta.x;

  point_scale(&delta, length);
  point_scale(&orth_delta, width/2.0);

  poly[0] = *to;
  point_sub(&poly[0], &delta);
  point_sub(&poly[0], &orth_delta);
  poly[1] = *to;
  poly[2] = *to;
  point_sub(&poly[2], &delta);
  point_add(&poly[2], &orth_delta);
}

/** Calculate the actual point of a crows-foot arrow.
 * @param poly A three-element array in which to return the three points
 *             involved in making a simple arrow: poly[0] is the tip, poly[1]
 *             is the right-hand point, and poly[2] is the left-hand point.
 * @param to Where the arrow is pointing to
 * @param from Where the arrow is pointing from (e.g. the end of the stem)
 * @param length How long the arrowhead should be.
 * @param width How wide the arrowhead should be.
 */
static void
calculate_crow(Point *poly, Point *to, Point *from,
               real length, real width)
{
  Point delta;
  Point orth_delta;
  real len;
  
  delta = *to;
  point_sub(&delta, from);
  len = point_len(&delta);
  if (len <= 0.0001) {
    delta.x=1.0;
    delta.y=0.0;
  } else {
    delta.x/=len;
    delta.y/=len;
  }

  orth_delta.x = delta.y;
  orth_delta.y = -delta.x;

  point_scale(&delta, length);
  point_scale(&orth_delta, width/2.0);

  poly[0] = *to;
  point_sub(&poly[0], &delta);
  poly[1] = *to;
  point_sub(&poly[1], &orth_delta);
  poly[2] = *to;
  point_add(&poly[2], &orth_delta);
}

/** Draw ER arrow for 0..N according to Modern database management,
 *  McFadden/Hoffer/Prescott, Addison-Wessley, 1999
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color Ignored.
 * @todo The ER-drawing methods are ripe for some refactoring.
 */
static void
draw_none_or_many(DiaRenderer *renderer, Point *to, Point *from,
                  real length, real width, real linewidth,
                  Color *fg_color,Color *bg_color)
{
  Point second_from, second_to;
  
  draw_crow_foot(renderer, to, from, length, width, 
                 linewidth, fg_color, bg_color);

  calculate_double_arrow(&second_to, &second_from, to, from, length);
  /* use the middle of the arrow */

  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);
 
  draw_empty_ellipse(renderer, &second_to, &second_from, length/2,
                     width, linewidth, fg_color);
}

/** ER arrow for exactly-one relations according to Modern database management,
 *  McFadden/Hoffer/Prescott, Addison-Wessley, 1999
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color Ignored.
 */
static void 
draw_one_exactly(DiaRenderer *renderer, Point *to, Point *from,
                  real length, real width, real linewidth,
                  Color *fg_color,Color *bg_color)
{
  Point vl,vt;
  Point bs,be;

  /* the first line */
  point_copy(&vl,from); point_sub(&vl,to);
  if (point_len(&vl) > 0)
    point_normalize(&vl);
  else {
    vl.x = 1.0; vl.y = 0.0;
  }
  if (!finite(vl.x)) {
    vl.x = 1.0; vl.y = 0.0;
  }
  point_get_perp(&vt,&vl);
  point_copy_add_scaled(&bs,to,&vl,length/2);
  point_copy_add_scaled(&be,&bs,&vt,-width/2.0);
  point_add_scaled(&bs,&vt,width/2.0);

  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer,&bs,&be,fg_color);

  point_copy_add_scaled(&bs,to,&vl,length);

  point_copy_add_scaled(&be,&bs,&vt,-width/2.0);
  point_add_scaled(&bs,&vt,width/2.0);

  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer,&bs,&be,fg_color);
}

/* ER arrow for 1..N according to Modern database management,
 * McFadden/Hoffer/Prescott, Addison-Wessley, 1999
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color Ignored.
 */
static void 
draw_one_or_many(DiaRenderer *renderer, Point *to, Point *from,
                 real length, real width, real linewidth,
                 Color *fg_color,Color *bg_color)
{

  Point poly[6];

  draw_crow_foot(renderer, to, from, length, width, 
                 linewidth, fg_color, bg_color);

  calculate_arrow(poly, to, from, length, width);
 
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);
 
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &poly[0],&poly[2], fg_color);
}

/* ER arrow for 0,1 according to Modern database management,
 * McFadden/Hoffer/Prescott, Addison-Wessley, 1999
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color Ignored.
 */
static void 
draw_one_or_none(DiaRenderer *renderer, Point *to, Point *from,
                  real length, real width, real linewidth,
                  Color *fg_color,Color *bg_color)
{
  Point vl,vt;
  Point bs,be;
  Point second_from, second_to;
  
  /* the  line */
  point_copy(&vl,from); point_sub(&vl,to);
  if (point_len(&vl) > 0)
    point_normalize(&vl);
  else {
    vl.x = 1.0; vl.y = 0.0;
  }
  if (!finite(vl.x)) {
    vl.x = 1.0; vl.y = 0.0;
  }
  point_get_perp(&vt,&vl);
  point_copy_add_scaled(&bs,to,&vl,length/2);
  point_copy_add_scaled(&be,&bs,&vt,-width/2.0);
  point_add_scaled(&bs,&vt,width/2.0);

  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer,&bs,&be,fg_color);
  /* the ellipse */
  calculate_double_arrow(&second_to, &second_from, to, from, length);
  draw_empty_ellipse(renderer, &second_to, &second_from, length/2, width, linewidth, fg_color); 
}

/** Draw a crow's foot arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color Ignored.
 */
static void 
draw_crow_foot(DiaRenderer *renderer, Point *to, Point *from,
               real length, real width, real linewidth,
               Color *fg_color,Color *bg_color)
{

  Point poly[3];

  calculate_crow(poly, to, from, length, width);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);

  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer,&poly[0],&poly[1],fg_color);
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer,&poly[0],&poly[2],fg_color);
}

/** Draw a simple open line arrow.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 */
static void
draw_lines(DiaRenderer *renderer, Point *to, Point *from,
           real length, real width, real linewidth,
           Color *color)
{
  Point poly[3];
    
  calculate_arrow(poly, to, from, length, width);
    
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);
    
  DIA_RENDERER_GET_CLASS(renderer)->draw_polyline(renderer, poly, 3, color);
}

/** Draw an arrowhead that is a filled ellipse.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color Used to fill the ellipse, usually white and non-settable.
 *                 If null, the ellipse is filled with fg_color and slightly
 *                 smaller (by linewidth/2).
 */
static void 
draw_fill_ellipse(DiaRenderer *renderer, Point *to, Point *from,
                  real length, real width, real linewidth,
                  Color *fg_color,Color *bg_color)
{
  BezPoint bp[5];
  Point vl,vt;

  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  if (!bg_color) {
    /* no bg_color means filled ellipse ; we then compensate for the line width
     */
    length += linewidth;
    width += linewidth;
  }
  point_copy(&vl,from); point_sub(&vl,to);
  if (point_len(&vl) > 0)
    point_normalize(&vl);
  else {
    vl.x = 1.0; vl.y = 0.0;
  }
  if (!finite(vl.x)) {
    vl.x = 1.0; vl.y = 0.0;
  }
  point_get_perp(&vt,&vl);


  /* This pile of crap is quite well handled by gcc. */ 
  bp[0].type = BEZ_MOVE_TO;
  point_copy(&bp[0].p1,to);
  bp[1].type = bp[2].type = bp[3].type = bp[4].type = BEZ_CURVE_TO;
  point_copy(&bp[4].p3,&bp[0].p1);

  point_copy_add_scaled(&bp[2].p3,&bp[0].p1,&vl,length);
  point_copy_add_scaled(&bp[2].p2,&bp[2].p3,&vt,-width / 4.0);
  point_copy_add_scaled(&bp[3].p1,&bp[2].p3,&vt,width / 4.0);
  point_copy_add_scaled(&bp[1].p1,&bp[0].p1,&vt,-width / 4.0);
  point_copy_add_scaled(&bp[4].p2,&bp[0].p1,&vt,width / 4.0);
  point_copy_add_scaled(&bp[1].p3,&bp[0].p1,&vl,length / 2.0); /* temp */
  point_copy_add_scaled(&bp[3].p3,&bp[1].p3,&vt,width / 2.0);
  point_add_scaled(&bp[1].p3,&vt,-width / 2.0);
  point_copy_add_scaled(&bp[1].p2,&bp[1].p3,&vl,-length / 4.0);
  point_copy_add_scaled(&bp[4].p1,&bp[3].p3,&vl,-length / 4.0);
  point_copy_add_scaled(&bp[2].p1,&bp[1].p3,&vl,length / 4.0);
  point_copy_add_scaled(&bp[3].p2,&bp[3].p3,&vl,length / 4.0);
  if (bg_color) {
    DIA_RENDERER_GET_CLASS(renderer)->fill_bezier(renderer,bp,sizeof(bp)/sizeof(bp[0]),bg_color);
    DIA_RENDERER_GET_CLASS(renderer)->draw_bezier(renderer,bp,sizeof(bp)/sizeof(bp[0]),fg_color);
  } else {
    DIA_RENDERER_GET_CLASS(renderer)->fill_bezier(renderer,bp,sizeof(bp)/sizeof(bp[0]),fg_color);
  }
}

/** Draw an arrowhead that is an ellipse with empty interior.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 */
static void
draw_empty_ellipse(DiaRenderer *renderer, Point *to, Point *from,
                  real length, real width, real linewidth,
                  Color *fg_color)
{
  BezPoint bp[5];
  Point vl,vt;
  Point disp;
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  point_copy(&vl,from);
  point_sub(&vl,to);
  if (point_len(&vl) > 0)
    point_normalize(&vl);
  else {
    vl.x = 1.0; vl.y = 0.0;
  }
  if (!finite(vl.x)) {
    vl.x = 1.0; vl.y = 0.0;
  }

  point_get_perp(&vt,&vl);
 
  point_copy(&disp, &vl);
  disp.x *= length/2;
  disp.y *= length/2;
  
  /* This pile of crap is quite well handled by gcc. */ 
  bp[0].type = BEZ_MOVE_TO;
  point_copy(&bp[0].p1,to);
  point_add(&bp[0].p1,&disp);
  bp[1].type = bp[2].type = bp[3].type = bp[4].type = BEZ_CURVE_TO;
  point_copy(&bp[4].p3,&bp[0].p1);

  point_copy_add_scaled(&bp[2].p3,&bp[0].p1,&vl,length);
  point_copy_add_scaled(&bp[2].p2,&bp[2].p3,&vt,-width / 4.0);
  point_copy_add_scaled(&bp[3].p1,&bp[2].p3,&vt,width / 4.0);
  point_copy_add_scaled(&bp[1].p1,&bp[0].p1,&vt,-width / 4.0);
  point_copy_add_scaled(&bp[4].p2,&bp[0].p1,&vt,width / 4.0);
  point_copy_add_scaled(&bp[1].p3,&bp[0].p1,&vl,length / 2.0); /* temp */
  point_copy_add_scaled(&bp[3].p3,&bp[1].p3,&vt,width / 2.0);
  point_add_scaled(&bp[1].p3,&vt,-width / 2.0);
  point_copy_add_scaled(&bp[1].p2,&bp[1].p3,&vl,-length / 4.0);
  point_copy_add_scaled(&bp[4].p1,&bp[3].p3,&vl,-length / 4.0);
  point_copy_add_scaled(&bp[2].p1,&bp[1].p3,&vl,length / 4.0);
  point_copy_add_scaled(&bp[3].p2,&bp[3].p3,&vl,length / 4.0);
  
  DIA_RENDERER_GET_CLASS(renderer)->draw_bezier(renderer,bp,sizeof(bp)/sizeof(bp[0]),fg_color);
}

/** Draw an arrow head that is an (optionall) filled box.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color The color used for the interior of the box.  If
 *                 fg_color == bg_color, the box is rendered slightly smaller.
 */
static void
draw_fill_box(DiaRenderer *renderer, Point *to, Point *from,
              real length, real width, real linewidth,
              Color *fg_color,Color *bg_color)
{
  Point vl,vt;
  Point bs,be;
  Point poly[4];
  real lw_factor,clength,cwidth;
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  if (fg_color == bg_color) {
    /* Filled dot */
    lw_factor = linewidth;
  } else {
    /* Hollow dot or dimension origin */
    lw_factor = 0.0;
  }
  clength = length + lw_factor;
  cwidth = width + lw_factor;

  point_copy(&vl,from); point_sub(&vl,to);
  if (point_len(&vl) > 0)
    point_normalize(&vl);
  else {
    vl.x = 1.0; vl.y = 0.0;
  }
  if (!finite(vl.x)) {
    vl.x = 1.0; vl.y = 0.0;
  }
  point_get_perp(&vt,&vl);

  point_copy_add_scaled(&bs,to,&vl,length/4);
  point_copy_add_scaled(&be,&bs,&vt,-width/2.0);
  point_add_scaled(&bs,&vt,width/2.0);
  
  point_copy(&poly[0],to);
  point_copy(&poly[1],&poly[0]);
  point_add_scaled(&poly[0],&vt,cwidth/4.0);
  point_add_scaled(&poly[1],&vt,-cwidth/4.0);
  point_copy_add_scaled(&poly[2],&poly[1],&vl,clength/2.0);
  point_copy_add_scaled(&poly[3],&poly[0],&vl,clength/2.0);

  if (fg_color == bg_color) {
    DIA_RENDERER_GET_CLASS(renderer)->fill_polygon(renderer, poly, 4, fg_color);
  } else {
    DIA_RENDERER_GET_CLASS(renderer)->fill_polygon(renderer, poly, 4, bg_color);
    DIA_RENDERER_GET_CLASS(renderer)->draw_polygon(renderer, poly, 4, fg_color);
  }
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer,&bs,&be,fg_color);
}

/** Draw a "filled dot" arrow.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color The collor used for the interior of the dot.
 * @bug Need to describe the diff between this and ellipse arrow.
 */
static void
draw_fill_dot(DiaRenderer *renderer, Point *to, Point *from,
              real length, real width, real linewidth,
              Color *fg_color,Color *bg_color)
{
  BezPoint bp[5];
  Point vl,vt;
  Point bs,be;
  real lw_factor,clength,cwidth;
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  if (fg_color == bg_color) {
    /* Filled dot */
    lw_factor = linewidth;
  } else {
    /* Hollow dot or dimension origin */
    lw_factor = 0.0;
  }
  clength = length + lw_factor;
  cwidth = width + lw_factor;

  point_copy(&vl,from); point_sub(&vl,to);
  if (point_len(&vl) > 0)
    point_normalize(&vl);
  else {
    vl.x = 1.0; vl.y = 0.0;
  }
  if (!finite(vl.x)) {
    vl.x = 1.0; vl.y = 0.0;
  }
  point_get_perp(&vt,&vl);

  point_copy_add_scaled(&bs,to,&vl,length/4);
  point_copy_add_scaled(&be,&bs,&vt,-width/2.0);
  point_add_scaled(&bs,&vt,width/2.0);
  
  /* This pile of crap is quite well handled by gcc. */ 
  bp[0].type = BEZ_MOVE_TO;
  point_copy(&bp[0].p1,to);
  bp[1].type = bp[2].type = bp[3].type = bp[4].type = BEZ_CURVE_TO;
  point_copy(&bp[4].p3,&bp[0].p1);

  point_copy_add_scaled(&bp[2].p3,&bp[0].p1,&vl,clength/2);
  point_copy_add_scaled(&bp[2].p2,&bp[2].p3,&vt,-cwidth / 8.0);
  point_copy_add_scaled(&bp[3].p1,&bp[2].p3,&vt,cwidth / 8.0);
  point_copy_add_scaled(&bp[1].p1,&bp[0].p1,&vt,-cwidth / 8.0);
  point_copy_add_scaled(&bp[4].p2,&bp[0].p1,&vt,cwidth / 8.0);
  point_copy_add_scaled(&bp[1].p3,&bp[0].p1,&vl,clength / 4.0); /* temp */
  point_copy_add_scaled(&bp[3].p3,&bp[1].p3,&vt,cwidth / 4.0);
  point_add_scaled(&bp[1].p3,&vt,-cwidth / 4.0);
  point_copy_add_scaled(&bp[1].p2,&bp[1].p3,&vl,-clength / 8.0);
  point_copy_add_scaled(&bp[4].p1,&bp[3].p3,&vl,-clength / 8.0);
  point_copy_add_scaled(&bp[2].p1,&bp[1].p3,&vl,clength / 8.0);
  point_copy_add_scaled(&bp[3].p2,&bp[3].p3,&vl,clength / 8.0);

  if (!bg_color) {
    /* Means dimension origin */
    Point dos,doe;

    point_copy_add_scaled(&doe,to,&vl,length);
    point_copy_add_scaled(&dos,to,&vl,length/2);
    
    DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer,&dos,&doe,fg_color);
  } else {
    DIA_RENDERER_GET_CLASS(renderer)->fill_bezier(renderer,bp,sizeof(bp)/sizeof(bp[0]),bg_color);
  }
  if (fg_color != bg_color) {
    DIA_RENDERER_GET_CLASS(renderer)->draw_bezier(renderer,bp,sizeof(bp)/sizeof(bp[0]),fg_color);
  }
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer,&bs,&be,fg_color);
}

/** Draw the integral-sign arrow head.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color The color used to kludge around the longer stem of this
 *                 arrow.
 * @bug The bg_color kludge should not be necessary, arrow pos is adjustable.
 */
static void
draw_integral(DiaRenderer *renderer, Point *to, Point *from,
              real length, real width, real linewidth,
              Color *fg_color)
{
  BezPoint bp[2];
  Point vl,vt;
  Point bs,be, bs2,be2;
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  point_copy(&vl,from); point_sub(&vl,to);
  if (point_len(&vl) > 0)
    point_normalize(&vl);
  else {
    vl.x = 1.0; vl.y = 0.0;
  }
  if (!finite(vl.x)) {
    vl.x = 1.0; vl.y = 0.0;
  }
  point_get_perp(&vt,&vl);

  point_copy_add_scaled(&bs,to,&vl,length/2);
  point_copy_add_scaled(&be,&bs,&vt,-width/2.0);
  point_add_scaled(&bs,&vt,width/2.0);

  point_copy_add_scaled(&bs2,to,&vl,length/2);
  point_copy_add_scaled(&be2,&bs2,&vl,length/2);
  
  bp[0].type = BEZ_MOVE_TO;
  bp[1].type = BEZ_CURVE_TO;
  point_copy_add_scaled(&bp[0].p1,to,&vl,.1*length);
  point_add_scaled(&bp[0].p1,&vt,.4*width);
  point_copy_add_scaled(&bp[1].p3,to,&vl,.9*length);
  point_add_scaled(&bp[1].p3,&vt,-.4*width);
  point_copy_add_scaled(&bp[1].p1,&bp[0].p1,&vl,.35*length);
  point_copy_add_scaled(&bp[1].p2,&bp[1].p3,&vl,-.35*length);

  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &bs2, &be2, fg_color);
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &bs, &be, fg_color);
  DIA_RENDERER_GET_CLASS(renderer)->draw_bezier(renderer,bp,sizeof(bp)/sizeof(bp[0]),fg_color);
}

/** Draw the arrowhead that is a line with a slash through it.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrow lines.
 * @param bg_color Used for a kludge of "erasing" the line tip instead of
 *                 figuring out the correct way to do this.
 * @bug Figure out the right way to do this, avoid kludge.
 */
static void
draw_slashed(DiaRenderer *renderer, Point *to, Point *from,
             real length, real width, real linewidth,
             Color *fg_color)
{
  Point vl,vt;
  Point bs,be, bs2,be2, bs3,be3;
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  point_copy(&vl,from); point_sub(&vl,to);
  if (point_len(&vl) > 0)
    point_normalize(&vl);
  else {
    vl.x = 1.0; vl.y = 0.0;
  }
  if (!finite(vl.x)) {
    vl.x = 1.0; vl.y = 0.0;
  }
  point_get_perp(&vt,&vl);

  point_copy_add_scaled(&bs,to,&vl,length/2);
  point_copy_add_scaled(&be,&bs,&vt,-width/2.0);
  point_add_scaled(&bs,&vt,width/2.0);

  point_copy_add_scaled(&bs2,to,&vl,length/2);
  point_copy_add_scaled(&be2,&bs2,&vl,length/2);
  
  point_copy_add_scaled(&bs3,to,&vl,.1*length);
  point_add_scaled(&bs3,&vt,.4*width);
  point_copy_add_scaled(&be3,to,&vl,.9*length);
  point_add_scaled(&be3,&vt,-.4*width);

  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &bs2, &be2, fg_color);
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &bs, &be, fg_color);
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &bs3, &be3, fg_color);
}

/** Calculate positions for the half-head arrow (only left-hand(?) line drawn)
 * @param poly The three-element array to store the result in.  
 * @param to Where the arrow points to
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrowhead
 * @param width The width of the arrowhead
 * @param linewidth The width of the lines used to draw the arrow
 * @bug Describe better what is put into poly.
 */
static void
calculate_halfhead(Point *poly, Point *to, Point *from,
                   real length, real width, real linewidth)
{
  Point delta;
  Point orth_delta;
  real len;
  real angle, add_len;

  if (width > 0.0000001) {
    angle = atan(length/(width/2));
    add_len = linewidth/cos(angle);
  } else {
    add_len = 0;
  }

  delta = *to;
  point_sub(&delta, from);
  len = point_len(&delta);
  if (len <= 0.0001) {
    delta.x=1.0;
    delta.y=0.0;
  } else {
    delta.x/=len;
    delta.y/=len;
  }

  orth_delta.x = delta.y;
  orth_delta.y = -delta.x;

  point_scale(&delta, length);
  point_scale(&orth_delta, width/2.0);

  poly[0] = *to;
  point_sub(&poly[0], &delta);
  point_sub(&poly[0], &orth_delta);
  poly[1] = *to;
  poly[2] = *to;
  point_normalize(&delta);
  point_scale(&delta, add_len);
  point_sub(&poly[2], &delta);
  /*  point_add(&poly[2], &orth_delta);*/
}

/** Draw a halfhead arrow.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrow lines.
 */
static void
draw_halfhead(DiaRenderer *renderer, Point *to, Point *from,
              real length, real width, real linewidth,
              Color *color)
{
  Point poly[3];

  calculate_halfhead(poly, to, from, length, width, linewidth);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);
    
  DIA_RENDERER_GET_CLASS(renderer)->draw_polyline(renderer, poly, 3, color);
}

/** Draw a basic triangular arrow.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrow lines.
 */
static void
draw_triangle(DiaRenderer *renderer, Point *to, Point *from,
              real length, real width, real linewidth,
              Color *color)
{
  Point poly[3];

  calculate_arrow(poly, to, from, length, width);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);

  DIA_RENDERER_GET_CLASS(renderer)->draw_polygon(renderer, poly, 3, color);
}

/** Draw a simple triangular arrow, with filled head.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrowhead.
 */
static void
fill_triangle(DiaRenderer *renderer, Point *to, Point *from,
              real length, real width, Color *color)
{
  Point poly[3];

  calculate_arrow(poly, to, from, length, width);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_fillstyle(renderer, FILLSTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);

  DIA_RENDERER_GET_CLASS(renderer)->fill_polygon(renderer, poly, 3, color);
}

/** Calculate the points needed to draw a diamon arrowhead.
 * @param poly A 4-element arrow to hold the return values:
 *             poly[0] holds the tip of the diamond.
 *             poly[1] holds the right-side tip of the diamond.
 *             poly[2] holds the back end of the diamond.
 *             poly[3] holds the left-side tip of the diamond.
 * @param to The point the arrow points to.
 * @param from The point the arrow points away from (e.g. bezier control line)
 * @param length The length of the arrowhead
 * @param width The width of the arrowhead
 * @bug Take linewidth into account.
 */
static void
calculate_diamond(Point *poly, Point *to, Point *from,
                  real length, real width)
{
  Point delta;
  Point orth_delta;
  real len;
  
  delta = *to;
  point_sub(&delta, from);
  len = sqrt(point_dot(&delta, &delta));
  if (len <= 0.0001) {
    delta.x=1.0;
    delta.y=0.0;
  } else {
    delta.x/=len;
    delta.y/=len;
  }

  orth_delta.x = delta.y;
  orth_delta.y = -delta.x;

  point_scale(&delta, length/2.0);
  point_scale(&orth_delta, width/2.0);
  
  poly[0] = *to;
  poly[1] = *to;
  point_sub(&poly[1], &delta);
  point_sub(&poly[1], &orth_delta);
  poly[2] = *to;
  point_sub(&poly[2], &delta);
  point_sub(&poly[2], &delta);
  poly[3] = *to;
  point_sub(&poly[3], &delta);
  point_add(&poly[3], &orth_delta);
}

/** Draw a diamond-shaped arrow head.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrowhead.
 */
static void
draw_diamond(DiaRenderer *renderer, Point *to, Point *from,
             real length, real width, real linewidth,
             Color *color)
{
  Point poly[4];

  calculate_diamond(poly, to, from, length, width);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  DIA_RENDERER_GET_CLASS(renderer)->draw_polygon(renderer, poly, 4, color);
}

/** Draw a right-hand part of a diamond arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrowhead.
*/
static void
draw_half_diamond(DiaRenderer *renderer, Point *to, Point *from,
                  real length, real width, real linewidth,
                  Color *color)
{
  Point poly[4];

  calculate_diamond(poly, to, from, length, width);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  DIA_RENDERER_GET_CLASS(renderer)->draw_polyline(renderer, poly+1, 3, color);
}

/** Draw a filled diamond arrow head.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param color The color used for drawing the arrowhead.
 */
static void
fill_diamond(DiaRenderer *renderer, Point *to, Point *from,
             real length, real width,
             Color *color)
{
  Point poly[4];

  calculate_diamond(poly, to, from, length, width);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  DIA_RENDERER_GET_CLASS(renderer)->fill_polygon(renderer, poly, 4, color);
}

/** Calculate the points needed to draw a slashed-cross arrowhead.
 * @param poly A 6-element array to hold the points calculated:
 * @param to Where the arrow points to.
 * @param from Where the arrow points from (e.g. other end of stem).
 * @param length The length of the arrowhead.
 * @param width The width of the arrowhead.
 * @bug Describe what is where in the poly array.
 */
static void
calculate_slashed_cross(Point *poly, Point *to, Point *from,
                        real length, real width)
{
  Point delta;
  Point orth_delta;
  real len;
  int i;
  
  delta = *to;
  point_sub(&delta, from);
  len = sqrt(point_dot(&delta, &delta));
  if (len <= 0.0001) {
    delta.x=1.0;
    delta.y=0.0;
  } else {
    delta.x/=len;
    delta.y/=len;
  }
  
  orth_delta.x = delta.y;
  orth_delta.y = -delta.x;

  point_scale(&delta, length/2.0);
  point_scale(&orth_delta, width/2.0);

  for(i=0; i<6;i++)poly[i] = *to;

  point_add(&poly[1], &delta);

  point_add(&poly[2], &delta);
  point_add(&poly[2], &orth_delta);

  point_sub(&poly[3], &delta);
  point_sub(&poly[3], &orth_delta);

  point_add(&poly[4], &orth_delta);
  point_sub(&poly[5], &orth_delta);
}

/** Draw a slashed cross arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrowhead.
 */
static void
draw_slashed_cross(DiaRenderer *renderer, Point *to, Point *from,
                   real length, real width, real linewidth, Color *color)
{
  Point poly[6];
  
  calculate_slashed_cross(poly, to, from, length, width);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);
  
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &poly[0],&poly[1], color);
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &poly[2],&poly[3], color);                   
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &poly[4],&poly[5], color);
}

/** Draw a backslash arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrowhead.
 * @todo refactor into calculate and draw.
 */
static void
draw_backslash(DiaRenderer *renderer, Point *to, Point *from,
               real length, real width, real linewidth, Color *color)
{
  Point point1;
  Point point2;
  Point delta;
  Point orth_delta;
  real len;

  delta = *to;
  point_sub(&delta, from);
  len = sqrt(point_dot(&delta, &delta));
  if (len <= 0.0001) {
    delta.x=1.0;
    delta.y=0.0;
  } else {
    delta.x/=len;
    delta.y/=len;
  }

  orth_delta.x = delta.y;
  orth_delta.y = -delta.x;

  point_scale(&delta, length/2.0);
  point_scale(&orth_delta, width/2.0);

  point1 = *to;
  point_sub(&point1, &delta);
  point_sub(&point1, &delta);
  point_sub(&point1, &delta);
  point_add(&point1, &orth_delta);

  point2 = *to;
  point_sub(&point2, &delta);
  point_sub(&point2, &orth_delta);

  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &point1,&point2, color);
}

/** Draw a cross-like arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrowhead.
 */
static void
draw_cross(DiaRenderer *renderer, Point *to, Point *from,
           real length, real width, real linewidth, Color *color)
{
  Point poly[6];
  
  calculate_arrow(poly, to, from, length, width);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);
  
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &poly[0],&poly[2], color);
  /*DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &poly[4],&poly[5], color); */
}

/** Calculate where to put the second arrowhead of a double arrow
 * @param second_to Return value for the point where the second arrowhead
 *                  should point to.
 * @param second_from Return value for the point where the second arrowhead
 *                  should point from.
 * @param to Where the first arrowhead should point to.
 * @param from Where the whole arrow points from (e.g. end of stem)
 * @param length The length of each arrowhead.
 */
static void
calculate_double_arrow(Point *second_to, Point *second_from, 
                       Point *to, Point *from, real length)
{
  Point delta;
  real len;
  
  delta = *to;
  point_sub(&delta, from);
  len = sqrt(point_dot(&delta, &delta));
  if (len <= 0.0001) {
    delta.x=1.0;
    delta.y=0.0;
  } else {
    delta.x/=len;
    delta.y/=len;
  }

  point_scale(&delta, length/2);
  
  *second_to = *to;
  point_sub(second_to, &delta);
  point_sub(second_to, &delta);
  *second_from = *from;
  point_add(second_from, &delta);
  point_add(second_from, &delta);
}

/** Draw a double-triangle arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrowhead.
 */
static void 
draw_double_triangle(DiaRenderer *renderer, Point *to, Point *from,
                     real length, real width, real linewidth, Color *color)
{
  Point second_from, second_to;
  
  draw_triangle(renderer, to, from, length, width, linewidth, color);
  calculate_double_arrow(&second_to, &second_from, to, from, length+linewidth);
  draw_triangle(renderer, &second_to, &second_from, length, width, linewidth, color);
}

/** Draw a filled double-triangle arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param color The color used for drawing the arrowhead.
 */
static void 
fill_double_triangle(DiaRenderer *renderer, Point *to, Point *from,
                     real length, real width, Color *color)
{
  Point second_from, second_to;
  
  fill_triangle(renderer, to, from, length, width, color);
  calculate_double_arrow(&second_to, &second_from, to, from, length);
  fill_triangle(renderer, &second_to, &second_from, length, width, color);
}

/** Calculate the points needed to draw a concave arrowhead.
 * @param poly A 4-element array of return points:
 *             poly[0] is the tip of the arrow.
 *             poly[1] is the right-hand point of the arrow.
 *             poly[2] is the rear indent point of the arrow.
 *             poly[3] is the left-hand point of the arrow.
 * @param to Where the arrow points to.
 * @param from Where the arrow points from (e.g. bezier control point)
 * @param length The length of the arrow.
 * @param width The width of the arrow.
 */
static void
calculate_concave(Point *poly, Point *to, Point *from,
                  real length, real width)
{
  Point delta;
  Point orth_delta;
  real len;
  
  delta = *to;
  point_sub(&delta, from);
  len = sqrt(point_dot(&delta, &delta));
  if (len <= 0.0001) {
    delta.x=1.0;
    delta.y=0.0;
  } else {
    delta.x/=len;
    delta.y/=len;
  }

  orth_delta.x = delta.y;
  orth_delta.y = -delta.x;

  point_scale(&delta, length/4.0);
  point_scale(&orth_delta, width/2.0);
  
  poly[0] = *to;
  poly[1] = *to;
  point_sub(&poly[1], &delta);
  point_sub(&poly[1], &delta);
  point_sub(&poly[1], &delta);
  point_sub(&poly[1], &delta);
  point_sub(&poly[1], &orth_delta);
  poly[2] = *to;
  point_sub(&poly[2], &delta);
  point_sub(&poly[2], &delta);
  point_sub(&poly[2], &delta);
  poly[3] = *to;
  point_add(&poly[3], &orth_delta);
  point_sub(&poly[3], &delta);
  point_sub(&poly[3], &delta);
  point_sub(&poly[3], &delta);
  point_sub(&poly[3], &delta);
}

/** Draw a concave triangle arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrowhead lines
 * @param bg_color The color used for drawing the arrowhead interior.
 */
static void
draw_concave_triangle(DiaRenderer *renderer, Point *to, Point *from,
                      real length, real width, real linewidth,
                      Color *fg_color, Color *bg_color)
{
  Point poly[4];

  calculate_concave(poly, to, from, length, width);
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);

  if (fg_color == bg_color)
    DIA_RENDERER_GET_CLASS(renderer)->fill_polygon(renderer, poly, 4, bg_color);
  DIA_RENDERER_GET_CLASS(renderer)->draw_polygon(renderer, poly, 4, fg_color);
}

/** Draw a rounded (half-circle) arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrowhead lines
 * @param bg_color Ignored.
 */
static void
draw_rounded(DiaRenderer *renderer, Point *to, Point *from,
             real length, real width, real linewidth,
             Color *fg_color, Color *bg_color)
{
  Point p = *to;
  Point delta;
  real len, rayon;
  real rapport;
  real angle_start;
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);
  
  delta = *from;
  
  point_sub(&delta, to);        
  
  len = sqrt(point_dot(&delta, &delta)); /* line length */
  rayon = (length / 2.0);
  rapport = rayon / len;
  
  p.x += delta.x * rapport;
  p.y += delta.y * rapport;
  
  angle_start = 90.0 - asin((p.y - to->y) / rayon) * (180.0 / 3.14);
  if (p.x - to->x < 0) { angle_start = 360.0 - angle_start;  }
  
  DIA_RENDERER_GET_CLASS(renderer)->draw_arc(renderer, &p, width, length, angle_start, angle_start - 180.0, fg_color);
  
  p.x += delta.x * rapport;
  p.y += delta.y * rapport;
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &p, to, fg_color);
}

/** Draw an open rounded arrowhead.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrowhead lines
 * @param bg_color Ignored.
 * @todo Describe the arrowhead better.
 */
static void
draw_open_rounded(DiaRenderer *renderer, Point *to, Point *from,
                  real length, real width, real linewidth,
                  Color *fg_color, Color *bg_color)
{
  Point p = *to;
  Point delta;
  real len, rayon;
  real rapport;
  real angle_start;
  Point p_line;

  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);
  
  delta = *from;
  
  point_sub(&delta, to);        
  
  len = sqrt(point_dot(&delta, &delta)); /* line length */
  rayon = (length / 2.0);
  rapport = rayon / len;
  
  p.x += delta.x * rapport;
  p.y += delta.y * rapport;
  
  angle_start = 90.0 - asin((p.y - to->y) / rayon) * (180.0 / 3.14);
  if (p.x - to->x < 0) { angle_start = 360.0 - angle_start;  }

  p_line = p;
  p_line.x += delta.x * rapport;
  p_line.y += delta.y * rapport;
  /*
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth * 2.0);
  DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &p_line, to, bg_color);
  */
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->draw_arc(renderer, &p, width, length, angle_start - 180.0, angle_start, fg_color);  
}

/** Draw an arrowhead with a circle in front of a triangle, filled.
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrowhead lines
 * @param bg_color Ignored.
 */
static void
draw_filled_dot_n_triangle(DiaRenderer *renderer, Point *to, Point *from,
                           real length, real width, real linewidth,
                           Color *fg_color, Color *bg_color)
{
  Point p_dot = *to, p_tri = *to, delta;
  real len, rayon;
  real rapport;
  Point poly[3];

  DIA_RENDERER_GET_CLASS(renderer)->set_linecaps(renderer, LINECAPS_BUTT);
  DIA_RENDERER_GET_CLASS(renderer)->set_linejoin(renderer, LINEJOIN_MITER);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  
  delta = *from;
  
  point_sub(&delta, to);        
  
  len = sqrt(point_dot(&delta, &delta)); /* line length */
  
  /* dot */
  rayon = (width / 2.0);
  rapport = rayon / len;
  p_dot.x += delta.x * rapport;
  p_dot.y += delta.y * rapport;
  DIA_RENDERER_GET_CLASS(renderer)->fill_ellipse(renderer, &p_dot,
                                                 width, width, fg_color);
  /* triangle */
  rapport = width / len;
  p_tri.x += delta.x * rapport;
  p_tri.y += delta.y * rapport;
  calculate_arrow(poly, &p_tri, from, length, width);
  DIA_RENDERER_GET_CLASS(renderer)->fill_polygon(renderer, poly, 3, fg_color);
}

/** Draw an arrowhead that is simply three dots (ellipsis)
 * @param renderer A renderer instance to draw into
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrowhead lines
 */
static void
draw_three_dots(DiaRenderer *renderer, Point *to, Point *from,
               real length, real width, real linewidth, Color *fg_color)
{

  gdouble dot_width;
  gdouble hole_width;
  gdouble len;
  gint i;
  Point delta, dot_from, dot_to;

  delta = *to;
  point_sub(&delta, from);
  len = point_len(&delta);
  point_normalize(&delta);

  if (len > 4 * width)
    width *= 2;
  dot_width = width * 0.2;
  hole_width = width / 3 - dot_width;
  
  DIA_RENDERER_GET_CLASS(renderer)->set_linewidth(renderer, linewidth);
  DIA_RENDERER_GET_CLASS(renderer)->set_linestyle(renderer, LINESTYLE_SOLID);

  for (i = 0; i < 3; i++) {
    dot_from.x = to->x - i  * (dot_width + hole_width) * delta.x;
    dot_from.y = to->y - i  * (dot_width + hole_width) * delta.y;
    dot_to.x = to->x - ((i + 1) * dot_width + i * hole_width) * delta.x;
    dot_to.y = to->y - ((i + 1) * dot_width + i * hole_width) * delta.y;
    DIA_RENDERER_GET_CLASS(renderer)->draw_line(renderer, &dot_from, &dot_to, fg_color);
  }
}

/** Draw any arrowhead.
 * @param renderer A renderer instance to draw into
 * @param type Which kind of arrowhead to draw.
 * @param to The point that the arrow points to.
 * @param from Where the arrow points from (e.g. end of stem)
 * @param length The length of the arrow
 * @param width The width of the arrow
 * @param linewidth The thickness of the lines used to draw the arrow.
 * @param fg_color The color used for drawing the arrowhead lines
 * @param bg_color The color used for drawing the arrowhead interior.
 */
void
arrow_draw(DiaRenderer *renderer, ArrowType type,
           Point *to, Point *from,
           real length, real width, real linewidth,
           Color *fg_color, Color *bg_color)
{
  switch(type) {
  case ARROW_NONE:
    break;
  case ARROW_LINES:
    draw_lines(renderer, to, from, length, width, linewidth, fg_color);
    break;
  case ARROW_HALF_HEAD:
    draw_halfhead(renderer, to, from, length, width, linewidth, fg_color);
    break;
  case ARROW_HOLLOW_TRIANGLE:
    fill_triangle(renderer, to, from, length, width, bg_color);
    draw_triangle(renderer, to, from, length, width, linewidth, fg_color);
    break;
  case ARROW_UNFILLED_TRIANGLE:
    draw_triangle(renderer, to, from, length, width, linewidth, fg_color);
    break;    
  case ARROW_FILLED_TRIANGLE:
    fill_triangle(renderer, to, from, length, width, fg_color);
    break;
  case ARROW_HOLLOW_DIAMOND:
    fill_diamond(renderer, to, from, length, width, bg_color);
    draw_diamond(renderer, to, from, length, width, linewidth, fg_color);
    break;
  case ARROW_FILLED_DIAMOND:
    fill_diamond(renderer, to, from, length, width, fg_color);
    break;
  case ARROW_HALF_DIAMOND:
    /*    fill_diamond(renderer, to, from, length, width, bg_color);*/
    draw_half_diamond(renderer, to, from, length, width, linewidth, fg_color);
    break;
  case ARROW_SLASHED_CROSS:
    draw_slashed_cross(renderer, to, from, length, width, linewidth, fg_color);
    break;
  case ARROW_FILLED_ELLIPSE:
    draw_fill_ellipse(renderer,to,from,length,width,linewidth,
                      fg_color,NULL);
    break;
  case ARROW_HOLLOW_ELLIPSE:
    draw_fill_ellipse(renderer,to,from,length,width,linewidth,
                      fg_color,bg_color);
    break;
  case ARROW_DOUBLE_HOLLOW_TRIANGLE:
    fill_double_triangle(renderer, to, from, length+(linewidth/2), width, bg_color);
    draw_double_triangle(renderer, to, from, length, width, linewidth, fg_color);  
    break;
  case ARROW_DOUBLE_FILLED_TRIANGLE:
    fill_double_triangle(renderer, to, from, length, width, fg_color);
    break;
  case ARROW_FILLED_DOT:
    draw_fill_dot(renderer,to,from,length,width,linewidth,fg_color,fg_color);
    break;
  case ARROW_BLANKED_DOT:
    draw_fill_dot(renderer,to,from,length,width,linewidth,fg_color,bg_color);
    break;
  case ARROW_FILLED_BOX:
    draw_fill_box(renderer,to,from,length,width,linewidth,fg_color,fg_color);
    break;
  case ARROW_BLANKED_BOX:
    draw_fill_box(renderer,to,from,length,width,linewidth,fg_color,bg_color);
    break;
  case ARROW_DIMENSION_ORIGIN:
    draw_fill_dot(renderer,to,from,length,width,linewidth,fg_color,NULL);
    break;
  case ARROW_INTEGRAL_SYMBOL:
    draw_integral(renderer,to,from,length,width,linewidth,fg_color);
    break;
  case ARROW_SLASH_ARROW:
    draw_slashed(renderer,to,from,length,width,linewidth,fg_color);
    break;
  case ARROW_ONE_OR_MANY:
    draw_one_or_many(renderer,to,from,length,width,linewidth,fg_color,bg_color);
    break;
  case ARROW_NONE_OR_MANY:
    draw_none_or_many(renderer,to,from,length,width,linewidth,fg_color,bg_color);
    break;
  case ARROW_ONE_EXACTLY:
    draw_one_exactly(renderer,to,from,length,width,linewidth,fg_color,bg_color);
    break;
  case ARROW_ONE_OR_NONE:
    draw_one_or_none(renderer,to,from,length,width,linewidth,fg_color,bg_color);
    break;
  case ARROW_CROW_FOOT:
    draw_crow_foot(renderer,to,from,length,width,linewidth,fg_color,bg_color);
    break;
  case ARROW_CROSS:
    draw_cross(renderer, to, from, length, width, linewidth, fg_color);
    break;
  case ARROW_FILLED_CONCAVE:
    draw_concave_triangle(renderer, to, from, length, width, linewidth, fg_color, fg_color);
    break;
  case ARROW_BLANKED_CONCAVE:
    draw_concave_triangle(renderer, to, from, length, width, linewidth, fg_color, bg_color);
    break;
  case ARROW_ROUNDED:
    draw_rounded(renderer, to, from, length, width, linewidth, fg_color, bg_color);
    break;
  case ARROW_OPEN_ROUNDED:
    draw_open_rounded(renderer, to, from, length, width, linewidth,
                      fg_color, bg_color);
    break;
  case ARROW_FILLED_DOT_N_TRIANGLE:
    draw_filled_dot_n_triangle(renderer, to, from, length, width, linewidth,
                               fg_color, bg_color);
    break;
  case ARROW_BACKSLASH:
    draw_backslash(renderer,to,from,length,width,linewidth,fg_color);
    break;
  case ARROW_THREE_DOTS:
    draw_three_dots(renderer,to,from,length,width,linewidth,fg_color);
    break;
      case MAX_ARROW_TYPE:
        break;
  } 
}

/* *** Loading and saving arrows. *** */
/** Makes sure an arrow object is within reasonable limits
 * @param arrow An arrow object.  This object may be modified to comply with
 * restrictions of MIN_ARROW_DIMENSION on its length and width and to have a 
 * legal head type.
 */
static void
sanitize_arrow(Arrow *arrow)
{
  if (arrow->length < MIN_ARROW_DIMENSION ||
      arrow->width < MIN_ARROW_DIMENSION ||
      arrow->type < 0 || arrow->type > MAX_ARROW_TYPE) {
    arrow->type = ARROW_NONE;
    arrow->width = DEFAULT_ARROW_WIDTH;
    arrow->length = DEFAULT_ARROW_LENGTH;
  }
}

/** Save the arrow information into three attributes.
 * @param obj_node The XML node to save to.
 * @param arrow the arrow to save.
 * @param type_attribute the name of the attribute of the arrow type.
 * @param length_attribute the name of the attribute of the arrow length.
 * @param width_attribute the name of the attribte of the arrow width.
 */
void
save_arrow(ObjectNode obj_node, Arrow *arrow, gchar *type_attribute,
           gchar *length_attribute, gchar *width_attribute)
{
  data_add_enum(new_attribute(obj_node, type_attribute),
                arrow->type);
  data_add_real(new_attribute(obj_node, length_attribute),
                arrow->length);
  data_add_real(new_attribute(obj_node, width_attribute),
                arrow->width);
}

/** Load arrow information from three attributes.
 * @param obj_node The XML node to load from.
 * @param arrow the arrow to store the data info.
 * @param type_attribute the name of the attribute of the arrow type.
 * @param length_attribute the name of the attribute of the arrow length.
 * @param width_attribute the name of the attribte of the arrow width.
 */
void
load_arrow(ObjectNode obj_node, Arrow *arrow, gchar *type_attribute, 
           gchar *length_attribute, gchar *width_attribute)
{
  AttributeNode *attr;

  arrow->type = ARROW_NONE;
  arrow->length = DEFAULT_ARROW_LENGTH;
  arrow->width = DEFAULT_ARROW_WIDTH;
  attr = object_find_attribute(obj_node, type_attribute);
  if (attr != NULL)
    arrow->type = data_enum(attribute_first_data(attr));
  attr = object_find_attribute(obj_node, length_attribute);
  if (attr != NULL)
    arrow->length = data_real(attribute_first_data(attr));
  attr = object_find_attribute(obj_node, width_attribute);
  if (attr != NULL)
    arrow->width = data_real(attribute_first_data(attr));

  sanitize_arrow(arrow);
}

/** Returns the arrow type that corresponds to a given name.
 * @param name The name of an arrow type (case sensitive)
 * @returns The arrow type (@see ArrowType enum in arrows.h).  Returns
 *          ARROW_NONE if the name doesn't match any known arrow head type.
 */
ArrowType
arrow_type_from_name(gchar *name)
{
  int i;
  for (i = 0; arrow_types[i].name != NULL; i++) {
    if (!strcmp(arrow_types[i].name, name)) {
      return arrow_types[i].enum_value;
    }
  }
  printf("Unknown arrow type %s\n", name);
  return 0;
}

/** Return the index into the arrow_types array (which is sorted by an
 * arbitrary order that we like) for a given arrow type.
 * @param atype An arrow type as defined in arrows.h
 * @returns An index into the arrow_types array.
 */
gint
arrow_index_from_type(ArrowType atype)
{
  int i = 0;

  for (i = 0; arrow_types[i].name != NULL; i++) {
    if (arrow_types[i].enum_value == atype) {
      return i;
    }
  }
  printf("Can't find arrow index for type %d\n", atype);
  return 0;
}

/** Get a list of all known arrow head names, in arrow_types order.
 * @returns A newly allocated list of the names.  The list should be 
 *          freed after use, but the strings are owned by arrow_types.
 */
GList *
get_arrow_names(void)
{
  int i = 0;
  GList *arrows = NULL;

  for (i = 0; arrow_types[i].name != NULL; i++) {
    arrows = g_list_append(arrows, arrow_types[i].name);
  }
  return arrows;
}