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planemo upload commit 2e9511a184a1ca667c7be0c6321a36dc4e3d116d
author jpayne
date Tue, 18 Mar 2025 16:23:26 -0400
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5 <title>cairo_path_t: Cairo: A Vector Graphics Library</title>
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21 <div class="sect1">
22 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
23 <a name="bindings-path"></a>cairo_path_t</h2></div></div></div>
24 <p>
25 The <a class="link" href="cairo-Paths.html#cairo-path-t" title="cairo_path_t"><span class="type">cairo_path_t</span></a> type is one
26 area in which most language bindings will differ significantly
27 from the C API. The C API for <span class="type">cairo_path_t</span> is
28 designed for efficiency and to avoid auxiliary objects that
29 would be have to be manually memory managed by the
30 application. However,
31 a language binding should not present <span class="type">cairo_path_t</span> as an
32 array, but rather as an opaque that can be iterated
33 over. Different languages have quite different conventions for
34 how iterators work, so it is impossible to give an exact
35 specification for how this API should work, but the type names
36 and methods should be similar to the language's mapping of the following:
37 </p>
38 <pre class="programlisting">
39 typedef struct cairo_path_iterator cairo_path_iterator_t;
40 typedef struct cairo_path_element cairo_path_element_t;
41
42 cairo_path_iterator_t *
43 cairo_path_get_iterator (cairo_path_t *path);
44
45 cairo_bool_t
46 cairo_path_iterator_has_next (cairo_path_iterator_t *iterator);
47
48 cairo_path_element_t *
49 cairo_path_iterator_next (cairo_path_iterator_t *iterator);
50
51 cairo_path_element_type_t
52 cairo_path_element_get_type (cairo_path_element_t *element);
53
54 void
55 cairo_path_element_get_point (cairo_path_element_t *element,
56 int index,
57 double *x,
58 double *y);
59 </pre>
60 <p>
61 The above is written using the Java conventions for
62 iterators. To illustrate how the API for PathIterator might
63 depend on the native iteration conventions of the API, examine
64 three versions of the loop, first written in a hypothetical Java
65 binding:
66 </p>
67 <pre class="programlisting">
68 PathIterator iter = cr.copyPath().iterator();
69 while (cr.hasNext()) {
70 PathElement element = iter.next();
71 if (element.getType() == PathElementType.MOVE_TO) {
72 Point p = element.getPoint(0);
73 doMoveTo (p.x, p.y);
74 }
75 }</pre>
76 <p>
77 And then in a hypothetical C++ binding:
78 </p>
79 <pre class="programlisting">
80 Path path = cr.copyPath();
81 for (PathIterator iter = path.begin(); iter != path.end(); iter++) {
82 PathElement element = *iter;
83 if (element.getType() == PathElementType.MOVE_TO) {
84 Point p = element.getPoint(0);
85 doMoveTo (p.x, p.y);
86 }
87 }</pre>
88 <p>
89 And then finally in a Python binding:
90 </p>
91 <pre class="programlisting">
92 for element in cr.copy_path():
93 if element.getType == cairo.PATH_ELEMENT_MOVE_TO:
94 (x, y) = element.getPoint(0)
95 doMoveTo (x, y);</pre>
96 <p>
97 While many of the API elements stay the same in the three
98 examples, the exact iteration mechanism is quite different, to
99 match how users of the language would expect to iterate over
100 a container.
101 </p>
102 <p>
103 You should not present an API for mutating or for creating new
104 <span class="type">cairo_path_t</span> objects. In the future, these
105 guidelines may be extended to present an API for creating a
106 <span class="type">cairo_path_t</span> from scratch for use with
107 <a class="link" href="cairo-Paths.html#cairo-append-path" title="cairo_append_path ()"><code class="function">cairo_append_path()</code></a>
108 but the current expectation is that <code class="function">cairo_append_path()</code> will
109 mostly be used with paths from
110 <a class="link" href="cairo-Paths.html#cairo-append-path" title="cairo_append_path ()"><code class="function">cairo_copy_path()</code></a>.
111 </p>
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