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+//----------------------------------------------------------------------------
+// Anti-Grain Geometry - Version 2.3
+// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
+//
+// Permission to copy, use, modify, sell and distribute this software
+// is granted provided this copyright notice appears in all copies.
+// This software is provided "as is" without express or implied
+// warranty, and with no claim as to its suitability for any purpose.
+//
+//----------------------------------------------------------------------------
+// Contact: mcseem@antigrain.com
+// mcseemagg@yahoo.com
+// http://www.antigrain.com
+//----------------------------------------------------------------------------
+//
+// classes conv_curve
+//
+//----------------------------------------------------------------------------
+
+#ifndef AGG_CONV_CURVE_INCLUDED
+#define AGG_CONV_CURVE_INCLUDED
+
+#include "agg_basics.h"
+#include "agg_curves.h"
+
+namespace agg
+{
+
+
+ //---------------------------------------------------------------conv_curve
+ // Curve converter class. Any path storage can have Bezier curves defined
+ // by their control points. There're two types of curves supported: curve3
+ // and curve4. Curve3 is a conic Bezier curve with 2 endpoints and 1 control
+ // point. Curve4 has 2 control points (4 points in total) and can be used
+ // to interpolate more complicated curves. Curve4, unlike curve3 can be used
+ // to approximate arcs, both curcular and elliptical. Curves are approximated
+ // with straight lines and one of the approaches is just to store the whole
+ // sequence of vertices that approximate our curve. It takes additional
+ // memory, and at the same time the consecutive vertices can be calculated
+ // on demand.
+ //
+ // Initially, path storages are not suppose to keep all the vertices of the
+ // curves (although, nothig prevents us from doing so). Instead, path_storage
+ // keeps only vertices, needed to calculate a curve on demand. Those vertices
+ // are marked with special commands. So, if the path_storage contains curves
+ // (which are not real curves yet), and we render this storage directly,
+ // all we will see is only 2 or 3 straight line segments (for curve3 and
+ // curve4 respectively). If we need to see real curves drawn we need to
+ // include this class into the conversion pipeline.
+ //
+ // Class conv_curve recognizes commands path_cmd_curve3 and path_cmd_curve4
+ // and converts these vertices into a move_to/line_to sequence.
+ //-----------------------------------------------------------------------
+ template<class VertexSource> class conv_curve
+ {
+ public:
+ conv_curve(VertexSource& source) :
+ m_source(&source), m_last_x(0.0), m_last_y(0.0) {}
+
+ void set_source(VertexSource& source) { m_source = &source; }
+
+ void approximation_scale(double s)
+ {
+ m_curve3.approximation_scale(s);
+ m_curve4.approximation_scale(s);
+ }
+
+ double approximation_scale() const
+ {
+ return m_curve3.approximation_scale();
+ }
+
+ void rewind(unsigned id);
+ unsigned vertex(double* x, double* y);
+
+ typedef conv_curve<VertexSource> source_type;
+ typedef vertex_iterator<source_type> iterator;
+ iterator begin(unsigned id) { return iterator(*this, id); }
+ iterator end() { return iterator(path_cmd_stop); }
+
+ private:
+ conv_curve(const conv_curve<VertexSource>&);
+ const conv_curve<VertexSource>&
+ operator = (const conv_curve<VertexSource>&);
+
+ VertexSource* m_source;
+ double m_last_x;
+ double m_last_y;
+ curve3 m_curve3;
+ curve4 m_curve4;
+ };
+
+
+
+ //------------------------------------------------------------------------
+ template<class VertexSource>
+ void conv_curve<VertexSource>::rewind(unsigned id)
+ {
+ m_source->rewind(id);
+ m_last_x = 0.0;
+ m_last_y = 0.0;
+ m_curve3.reset();
+ m_curve4.reset();
+ }
+
+
+ //------------------------------------------------------------------------
+ template<class VertexSource>
+ unsigned conv_curve<VertexSource>::vertex(double* x, double* y)
+ {
+ if(!is_stop(m_curve3.vertex(x, y)))
+ {
+ m_last_x = *x;
+ m_last_y = *y;
+ return path_cmd_line_to;
+ }
+
+ if(!is_stop(m_curve4.vertex(x, y)))
+ {
+ m_last_x = *x;
+ m_last_y = *y;
+ return path_cmd_line_to;
+ }
+
+ double ct2_x = 0;
+ double ct2_y = 0;
+ double end_x = 0;
+ double end_y = 0;
+
+ unsigned cmd = m_source->vertex(x, y);
+ switch(cmd)
+ {
+ case path_cmd_move_to:
+ case path_cmd_line_to:
+ m_last_x = *x;
+ m_last_y = *y;
+ default:
+ break;
+
+ case path_cmd_curve3:
+ m_source->vertex(&end_x, &end_y);
+
+ m_curve3.init(m_last_x, m_last_y,
+ *x, *y,
+ end_x, end_y);
+
+ m_curve3.vertex(x, y); // First call returns path_cmd_move_to
+ m_curve3.vertex(x, y); // This is the first vertex of the curve
+ cmd = path_cmd_line_to;
+ break;
+
+ case path_cmd_curve4:
+ m_source->vertex(&ct2_x, &ct2_y);
+ m_source->vertex(&end_x, &end_y);
+
+ m_curve4.init(m_last_x, m_last_y,
+ *x, *y,
+ ct2_x, ct2_y,
+ end_x, end_y);
+
+ m_curve4.vertex(x, y); // First call returns path_cmd_move_to
+ m_curve4.vertex(x, y); // This is the first vertex of the curve
+ cmd = path_cmd_line_to;
+ break;
+ }
+ return cmd;
+ }
+
+
+}
+
+
+
+#endif