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  1. /* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
  2. /* cairo - a vector graphics library with display and print output
  3.  *
  4.  * Copyright © 2002 University of Southern California
  5.  *
  6.  * This library is free software; you can redistribute it and/or
  7.  * modify it either under the terms of the GNU Lesser General Public
  8.  * License version 2.1 as published by the Free Software Foundation
  9.  * (the "LGPL") or, at your option, under the terms of the Mozilla
  10.  * Public License Version 1.1 (the "MPL"). If you do not alter this
  11.  * notice, a recipient may use your version of this file under either
  12.  * the MPL or the LGPL.
  13.  *
  14.  * You should have received a copy of the LGPL along with this library
  15.  * in the file COPYING-LGPL-2.1; if not, write to the Free Software
  16.  * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
  17.  * You should have received a copy of the MPL along with this library
  18.  * in the file COPYING-MPL-1.1
  19.  *
  20.  * The contents of this file are subject to the Mozilla Public License
  21.  * Version 1.1 (the "License"); you may not use this file except in
  22.  * compliance with the License. You may obtain a copy of the License at
  23.  * http://www.mozilla.org/MPL/
  24.  *
  25.  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
  26.  * OF ANY KIND, either express or implied. See the LGPL or the MPL for
  27.  * the specific language governing rights and limitations.
  28.  *
  29.  * The Original Code is the cairo graphics library.
  30.  *
  31.  * The Initial Developer of the Original Code is University of Southern
  32.  * California.
  33.  *
  34.  * Contributor(s):
  35.  *      Carl D. Worth <cworth@cworth.org>
  36.  *      Chris Wilson <chris@chris-wilson.co.uk>
  37.  */
  38.  
  39. #include "cairoint.h"
  40.  
  41. #include "cairo-stroke-dash-private.h"
  42.  
  43. void
  44. _cairo_stroker_dash_start (cairo_stroker_dash_t *dash)
  45. {
  46.     double offset;
  47.     cairo_bool_t on = TRUE;
  48.     unsigned int i = 0;
  49.  
  50.     if (! dash->dashed)
  51.         return;
  52.  
  53.     offset = dash->dash_offset;
  54.  
  55.     /* We stop searching for a starting point as soon as the
  56.        offset reaches zero.  Otherwise when an initial dash
  57.        segment shrinks to zero it will be skipped over. */
  58.     while (offset > 0.0 && offset >= dash->dashes[i]) {
  59.         offset -= dash->dashes[i];
  60.         on = !on;
  61.         if (++i == dash->num_dashes)
  62.             i = 0;
  63.     }
  64.  
  65.     dash->dash_index = i;
  66.     dash->dash_on = dash->dash_starts_on = on;
  67.     dash->dash_remain = dash->dashes[i] - offset;
  68. }
  69.  
  70. void
  71. _cairo_stroker_dash_step (cairo_stroker_dash_t *dash, double step)
  72. {
  73.     dash->dash_remain -= step;
  74.     if (dash->dash_remain < CAIRO_FIXED_ERROR_DOUBLE) {
  75.         if (++dash->dash_index == dash->num_dashes)
  76.             dash->dash_index = 0;
  77.  
  78.         dash->dash_on = ! dash->dash_on;
  79.         dash->dash_remain += dash->dashes[dash->dash_index];
  80.     }
  81. }
  82.  
  83. void
  84. _cairo_stroker_dash_init (cairo_stroker_dash_t *dash,
  85.                           const cairo_stroke_style_t *style)
  86. {
  87.     dash->dashed = style->dash != NULL;
  88.     if (! dash->dashed)
  89.         return;
  90.  
  91.     dash->dashes = style->dash;
  92.     dash->num_dashes = style->num_dashes;
  93.     dash->dash_offset = style->dash_offset;
  94.  
  95.     _cairo_stroker_dash_start (dash);
  96. }
  97.