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.. _Associative Sequence: http://www.boost.org/doc/libs/1_56_0/libs/mpl/doc/refmanual/associative-sequence.html
.. _basic_shapes:
Basic Shapes
====================
`Basic shapes <http://www.w3.org/TR/SVG/shapes.html>`_ (**rect**, **circle**, **ellipse**, **line**, **polyline**
and **polygon**) can be automatically converted to *path* commands.
Basic Shapes Policy Concept
--------------------------------
::
struct basic_shapes_policy
{
typedef /* Associative Sequence */ convert_to_path;
typedef /* Associative Sequence */ collect_attributes;
static const bool convert_only_rounded_rect_to_path = /* true or false */;
};
``convert_to_path``
`Associative Sequence`_ (e.g. ``boost::mpl::set``), containing SVG *basic shapes* elements tags,
which will be converted to **path**. Generated **path** uses *Path Policy* and *Path Events Policy* settings.
``collect_attributes``
`Associative Sequence`_, containing any of **rect**, **circle**, **ellipse** or **line** element tags.
Geometry of elements included in the sequence will be passed with single call instead of separate attribute
handling (see *Basic Shapes Events Policy*).
``convert_only_rounded_rect_to_path``
If static member constant ``convert_only_rounded_rect_to_path`` equals to ``true`` and
``tag::element::rect`` is included in ``convert_to_path`` sequence,
then only rounded rectangles will be converted to **path**,
and regular rectangles will be handle like if ``tag::element::rect`` is included in ``collect_attributes``.
In ``document_traversal`` processing of attributes describing *basic shapes* geometry (**x**, **y**,
**r** etc) must be :ref:`enabled <processed_attributes>`,
i. e. they must be included in ``processed_attributes`` or excluded from ``ignored_attributes``.
`Associative Sequence`_ ``traits::shapes_attributes_by_element`` contains tags of all such attributes
for *basic shapes*.
:ref:`Named class template parameter <named-params>` for *Basic Shapes Policy* is ``basic_shapes_policy``.
Basic Shapes Events Policy Concept
-------------------------------------
::
struct basic_shapes_events_policy
{
static void set_rect(Context & context, Coordinate x, Coordinate y, Coordinate width, Coordinate height,
Coordinate rx, Coordinate ry);
static void set_rect(Context & context, Coordinate x, Coordinate y, Coordinate width, Coordinate height);
static void set_line(Context & context, Coordinate x1, Coordinate y1, Coordinate x2, Coordinate y2);
static void set_circle(Context & context, Coordinate cx, Coordinate cy, Coordinate r);
static void set_ellipse(Context & context, Coordinate cx, Coordinate cy, Coordinate rx, Coordinate ry);
};
*Basic Shapes Events Policy* is used for *basic shapes* (except **polyline** and **polygon**) elements,
that are listed in ``collect_attributes`` field of *Basic Shapes Policy*.
Adapters that implement these conversions, use ``length_to_user_coordinate`` method of *Length Factory*
to get *user coordinates* value by *length*. These adapters passes default values if attributes are missing
and check correctness of attributes. If value disables rendering of the element
according to SVG specification, then *Basic Shapes Events Policy* methods aren't called,
and if an attribute has negative value that is not permitted by specification,
then ``negative_value`` function of :ref:`Error Policy <error_policy>` is called.
Default *Basic Shapes Events Policy* (``policy::basic_shapes_events::forward_to_method``)
forwards calls to its static methods to ``context`` object methods::
struct forward_to_method
{
template<class Coordinate>
static void set_rect(Context & context, Coordinate x, Coordinate y, Coordinate width, Coordinate height,
Coordinate rx, Coordinate ry)
{
context.set_rect(x, y, width, height, rx, ry);
}
/*...*/
};
:ref:`Named class template parameter <named-params>` for *Basic Shapes Events Policy* is ``basic_shapes_events_policy``.
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