source/libs/cairo/cairo-src/src/cairo-stroke-dash.c

   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 }