sample01e.cpp

#include <rapidxml_ns/rapidxml_ns.hpp>
#include <svgpp/policy/xml/rapidxml_ns.hpp>
#include <svgpp/svgpp.hpp>

using namespace svgpp;

typedef rapidxml_ns::xml_node<> const * xml_element_t;

class BaseContext
{
public:
  void on_exit_element()
  {}

  void transform_matrix(const boost::array<double, 6> & matrix)
  {}

  void set_viewport(double viewport_x, double viewport_y, double viewport_width, double viewport_height)
  {}

  void set_viewbox_size(double viewbox_width, double viewbox_height)
  {}

  void disable_rendering()
  {}
};

class ShapeContext: public BaseContext
{
public:
  ShapeContext(BaseContext const & parent)
  {}

  void path_move_to(double x, double y, tag::coordinate::absolute)
  {}

  void path_line_to(double x, double y, tag::coordinate::absolute)
  {}

  void path_cubic_bezier_to(
    double x1, double y1,
    double x2, double y2,
    double x, double y,
    tag::coordinate::absolute)
  {}

  void path_quadratic_bezier_to(
    double x1, double y1,
    double x, double y,
    tag::coordinate::absolute)
  {}

  void path_elliptical_arc_to(
    double rx, double ry, double x_axis_rotation,
    bool large_arc_flag, bool sweep_flag,
    double x, double y,
    tag::coordinate::absolute)
  {}

  void path_close_subpath()
  {}

  void path_exit()
  {}
};

class UseContext: public BaseContext
{
public:
  UseContext(BaseContext const & parent)
  {}

  boost::optional<double> const & width() const { return width_; }
  boost::optional<double> const & height() const { return height_; }

  template<class IRI>
  void set(tag::attribute::xlink::href, tag::iri_fragment, IRI const & fragment)
  { fragment_id_.assign(boost::begin(fragment), boost::end(fragment)); }

  template<class IRI>
  void set(tag::attribute::xlink::href, IRI const & fragment)
  { std::cerr << "External references aren't supported\n"; }

  void set(tag::attribute::x, double val)
  { x_ = val; }

  void set(tag::attribute::y, double val)
  { y_ = val; }

  void set(tag::attribute::width, double val)
  { width_ = val; }

  void set(tag::attribute::height, double val)
  { height_ = val; }

  void on_exit_element();

private:
  std::string fragment_id_;
  double x_, y_;
  boost::optional<double> width_, height_;
};

class ReferencedSymbolOrSvgContext: 
  public BaseContext
{
public:
  ReferencedSymbolOrSvgContext(UseContext & referencing)
    : BaseContext(referencing)
    , referencing_(referencing)
  {
  }

  void get_reference_viewport_size(double & width, double & height)
  {
    if (referencing_.width())
      width = *referencing_.width();
    if (referencing_.height())
      height = *referencing_.height();
  }

private:
  UseContext & referencing_;
};

struct ChildContextFactories
{
  template<class ParentContext, class ElementTag, class Enable = void>
  struct apply
  {
    // Default definition handles "svg" and "g" elements
    typedef factory::context::on_stack<BaseContext> type;
  };
};

// This specialization handles all shape elements (elements from traits::shape_elements sequence)
template<class ElementTag>
struct ChildContextFactories::apply<BaseContext, ElementTag,
  typename boost::enable_if<boost::mpl::has_key<traits::shape_elements, ElementTag> >::type>
{
  typedef factory::context::on_stack<ShapeContext> type;
};

template<>
struct ChildContextFactories::apply<BaseContext, tag::element::use_>
{
  typedef factory::context::on_stack<UseContext> type;
};

// Elements referenced by 'use' element
template<>
struct ChildContextFactories::apply<UseContext, tag::element::svg, void>
{
  typedef factory::context::on_stack<ReferencedSymbolOrSvgContext> type;
};

template<>
struct ChildContextFactories::apply<UseContext, tag::element::symbol, void>
{
  typedef factory::context::on_stack<ReferencedSymbolOrSvgContext> type;
};

template<class ElementTag>
struct ChildContextFactories::apply<UseContext, ElementTag, void>: ChildContextFactories::apply<BaseContext, ElementTag>
{};

template<class ElementTag>
struct ChildContextFactories::apply<ReferencedSymbolOrSvgContext, ElementTag, void>: 
  ChildContextFactories::apply<BaseContext, ElementTag>
{};

typedef 
  boost::mpl::set<
    // SVG Structural Elements
    tag::element::svg,
    tag::element::g,
    tag::element::use_,
    // SVG Shape Elements
    tag::element::circle,
    tag::element::ellipse,
    tag::element::line,
    tag::element::path,
    tag::element::polygon,
    tag::element::polyline,
    tag::element::rect
  >::type processed_elements_t;

// This cryptic code just merges predefined sequences traits::shapes_attributes_by_element
// and traits::viewport_attributes with tag::attribute::transform and tag::attribute::xlink::href 
// attributes into single MPL sequence
typedef 
  boost::mpl::fold<
    boost::mpl::protect<
      boost::mpl::joint_view<
        traits::shapes_attributes_by_element, 
        traits::viewport_attributes
      >
    >,
    boost::mpl::set<
      tag::attribute::transform,
      boost::mpl::pair<tag::element::use_, tag::attribute::xlink::href>
    >::type,
    boost::mpl::insert<boost::mpl::_1, boost::mpl::_2>
  >::type processed_attributes_t;

typedef
  document_traversal<
    processed_elements<processed_elements_t>,
    processed_attributes<processed_attributes_t>,
    viewport_policy<policy::viewport::as_transform>,
    context_factories<ChildContextFactories>
  > document_traversal_t;

void loadSvg(xml_element_t xml_root_element)
{
  BaseContext context;
  document_traversal_t::load_document(xml_root_element, context);
}

xml_element_t FindCurrentDocumentElementById(std::string const &) 
{ 
  // To be implemented.
  return NULL; 
}

void UseContext::on_exit_element()
{
  if (xml_element_t element = FindCurrentDocumentElementById(fragment_id_))
  {
    // TODO: Check for cyclic references
    // TODO: Apply translate transform (x_, y_)
    document_traversal_t::load_referenced_element<
      referencing_element<tag::element::use_>,
      expected_elements<traits::reusable_elements>,
      processed_elements<
        boost::mpl::insert<processed_elements_t, tag::element::symbol>::type 
      >
    >::load(element, *this);
  }
  else
    std::cerr << "Element referenced by 'use' not found\n";
}

int main()
{
#define TEXT(x) #x
  char text[] = 
    TEXT(<svg width="10cm" height="3cm" viewBox="0 0 100 30" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">)
    TEXT( <defs>)
    TEXT(  <rect id="MyRect" width="60" height="10"/>)
    TEXT( </defs>)
    TEXT( <rect x=".1" y=".1" width="99.8" height="29.8"/>)
    TEXT( <use x="20" y="10" xlink:href="#MyRect"/>)
    TEXT(</svg>);

  rapidxml_ns::xml_document<> doc;    // character type defaults to char
  try
  {
    doc.parse<0>(text);  
    if (rapidxml_ns::xml_node<> * svg_element = doc.first_node("svg"))
    {
      loadSvg(svg_element);
    }
  }
  catch (std::exception const & e)
  {
    std::cerr << "Error loading SVG: " << e.what() << std::endl;
    return 1;
  }

  return 0;
}