/* Libart_LGPL - library of basic graphic primitives
* Copyright (C) 1999-2000 Raph Levien
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/* Apply a dash style to a vector path. */
#include "config.h"
#include "art_vpath_dash.h"
#include <math.h>
#include <stdlib.h>
#include "art_misc.h"
#include "art_vpath.h"
/* Return the length of the largest subpath within vpath */
static gint
art_vpath_dash_max_subpath (const ArtVpath *vpath)
{
gint max_subpath;
gint i;
gint start;
max_subpath = 0;
start = 0;
for (i = 0; vpath[i].code != ART_END; i++)
{
if (vpath[i].code == ART_MOVETO || vpath[i].code == ART_MOVETO_OPEN)
{
if (i - start > max_subpath)
max_subpath = i - start;
start = i;
}
}
if (i - start > max_subpath)
max_subpath = i - start;
return max_subpath;
}
/**
* art_vpath_dash: Add dash style to vpath.
* @vpath: Original vpath.
* @dash: Dash style.
*
* Creates a new vpath that is the result of applying dash style @dash
* to @vpath.
*
* This implementation has two known flaws:
*
* First, it adds a spurious break at the beginning of the vpath. The
* only way I see to resolve this flaw is to run the state forward one
* dash break at the beginning, and fix up by looping back to the
* first dash break at the end. This is doable but of course adds some
* complexity.
*
* Second, it does not suppress output points that are within epsilon
* of each other.
*
* Return value: Newly created vpath.
**/
ArtVpath *
art_vpath_dash (const ArtVpath *vpath, const ArtVpathDash *dash)
{
gint max_subpath;
gdouble *dists;
ArtVpath *result;
gint n_result, n_result_max;
gint start, end;
gint i;
gdouble total_dist;
/* state while traversing dasharray - offset is offset of current dash
value, toggle is 0 for "off" and 1 for "on", and phase is the distance
in, >= 0, < dash->dash[offset]. */
gint offset, toggle;
gdouble phase;
/* initial values */
gint offset_init, toggle_init;
gdouble phase_init;
max_subpath = art_vpath_dash_max_subpath (vpath);
dists = art_new (double, max_subpath);
n_result = 0;
n_result_max = 16;
result = art_new (ArtVpath, n_result_max);
/* determine initial values of dash state */
toggle_init = 1;
offset_init = 0;
phase_init = dash->offset;
while (phase_init >= dash->dash[offset_init])
{
toggle_init = !toggle_init;
phase_init -= dash->dash[offset_init];
offset_init++;
if (offset_init == dash->n_dash)
offset_init = 0;
}
for (start = 0; vpath[start].code != ART_END; start = end)
{
for (end = start + 1; vpath[end].code == ART_LINETO; end++);
/* subpath is [start..end) */
total_dist = 0;
for (i = start; i < end - 1; i++)
{
gdouble dx, dy;
dx = vpath[i + 1].x - vpath[i].x;
dy = vpath[i + 1].y - vpath[i].y;
dists[i - start] = sqrt (dx * dx + dy * dy);
total_dist += dists[i - start];
}
if (total_dist <= dash->dash[offset_init] - phase_init)
{
/* subpath fits entirely within first dash */
if (toggle_init)
{
for (i = start; i < end; i++)
art_vpath_add_point (&result, &n_result, &n_result_max,
vpath[i].code, vpath[i].x, vpath[i].y);
}
}
else
{
/* subpath is composed of at least one dash - thus all
generated pieces are open */
gdouble dist;
phase = phase_init;
offset = offset_init;
toggle = toggle_init;
dist = 0;
i = start;
if (toggle)
art_vpath_add_point (&result, &n_result, &n_result_max,
ART_MOVETO_OPEN, vpath[i].x, vpath[i].y);
while (i != end - 1)
{
if (dists[i - start] - dist > dash->dash[offset] - phase)
{
/* dash boundary is next */
gdouble a;
gdouble x, y;
dist += dash->dash[offset] - phase;
a = dist / dists[i - start];
x = vpath[i].x + a * (vpath[i + 1].x - vpath[i].x);
y = vpath[i].y + a * (vpath[i + 1].y - vpath[i].y);
art_vpath_add_point (&result, &n_result, &n_result_max,
toggle ? ART_LINETO : ART_MOVETO_OPEN,
x, y);
/* advance to next dash */
toggle = !toggle;
phase = 0;
offset++;
if (offset == dash->n_dash)
offset = 0;
}
else
{
/* end of line in vpath is next */
phase += dists[i - start] - dist;
i++;
dist = 0;
if (toggle)
art_vpath_add_point (&result, &n_result, &n_result_max,
ART_LINETO, vpath[i].x, vpath[i].y);
}
}
}
}
art_vpath_add_point (&result, &n_result, &n_result_max,
ART_END, 0, 0);
art_free (dists);
return result;
}
