cpml/cpml-close.c

   1 /* CPML - Cairo Path Manipulation Library
   2  * Copyright (C) 2008, 2009  Nicola Fontana <ntd at entidi.it>
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the
  16  * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  17  * Boston, MA  02110-1301, USA.
  18  */
  19
  20 /**
  21  * SECTION:close
  22  * @title: Closing path lines
  23  * @short_description: APIs to manage closing path virtual primitives
  24  *
  25  * The following functions manipulate %CAIRO_PATH_CLOSE_PATH
  26  * #CpmlPrimitive. No check is made on the primitive struct, so be
  27  * sure the <structname>CpmlPrimitive</structname> is effectively
  28  * a close operation before calling these APIs.
  29  *
  30  * This primitive management is almost identical to straight lines,
  31  * but taking properly start and end points.
  32  **/
  33
  34 #include "cpml-close.h"
  35 #include "cpml-pair.h"
  36 #include "cpml-line.h"
  37
  38 /**
  39  * cpml_close_type_get_npoints:
  40  *
  41  * Returns the number of points needed to properly specify a close primitive.
  42  * This is a bit tricky: the close path primitive can be specified with
  43  * a single point but it has an implicit second point, the start point
  44  * of the source segment. This means retrieving a second point from a
  45  * cairo path is a valid operation and must return the start point of
  46  * the source segment.
  47  *
  48  * Return value: 2
  49  **/
  50 int
  51 cpml_close_type_get_npoints(void)
  52 {
  53     return 2;
  54 }
  55
  56 /**
  57  * cpml_close_pair_at:
  58  * @close: the #CpmlPrimitive close data
  59  * @pair: the destination pair
  60  * @pos:  the position value
  61  *
  62  * Given the @close path virtual primitive, finds the coordinates
  63  * at position @pos (where 0 is the start and 1 is the end) and
  64  * stores the result in @pair.
  65  *
  66  * @pos can be less than 0 or greater than 1, in which case the
  67  * coordinates are interpolated.
  68  **/
  69 void
  70 cpml_close_pair_at(const CpmlPrimitive *close, CpmlPair *pair, double pos)
  71 {
  72     cpml_line_pair_at(close, pair, pos);
  73 }
  74
  75 /**
  76  * cpml_close_vector_at:
  77  * @close:  the #CpmlPrimitive close data
  78  * @vector: the destination vector
  79  * @pos:    the position value
  80  *
  81  * Gets the slope on @close at the position @pos. Being the
  82  * close a straight line, the vector is always the same, so
  83  * @pos is not used.
  84  **/
  85 void
  86 cpml_close_vector_at(const CpmlPrimitive *close,
  87                      CpmlVector *vector, double pos)
  88 {
  89     cpml_line_vector_at(close, vector, pos);
  90 }
  91
  92 /**
  93  * cpml_close_near_pos:
  94  * @close: the #CpmlPrimitive close data
  95  * @pair: the coordinates of the subject point
  96  *
  97  * Returns the pos value of the point on @close nearest to @pair.
  98  * The returned value is always between 0 and 1.
  99  *
 100  * Return value: the pos value, always between 0 and 1
 101  **/
 102 double
 103 cpml_close_near_pos(const CpmlPrimitive *close, const CpmlPair *pair)
 104 {
 105     return cpml_line_near_pos(close, pair);
 106 }
 107
 108 /**
 109  * cpml_close_offset:
 110  * @close:  the #CpmlPrimitive close data
 111  * @offset: distance for the computed parallel close
 112  *
 113  * Given a close segment specified by the @close primitive data,
 114  * computes the parallel close distant @offset from the original one
 115  * and returns the result by changing @close.
 116  **/
 117 void
 118 cpml_close_offset(CpmlPrimitive *close, double offset)
 119 {
 120     cpml_line_offset(close, offset);
 121 }