add geom-nodetype. helper function to determine the nodetype between two curves

(bzr r6295)

3 files changed, 130 insertions, 0 deletions

diff --git a/src/helper/Makefile_insert b/src/helper/Makefile_insert
index 99957ab3b..20c7e6c53 100644
--- a/src/helper/Makefile_insert
+++ b/src/helper/Makefile_insert
@@ -18,6 +18,8 @@ helper_libspchelp_a_SOURCES =	\
 	helper/action.h	\
 	helper/geom.cpp	\
 	helper/geom.h	\
+	helper/geom-nodetype.cpp	\
+	helper/geom-nodetype.h	\
 	helper/gnome-utils.cpp	\
 	helper/gnome-utils.h	\
 	helper/helper-forward.h	\
diff --git a/src/helper/geom-nodetype.cpp b/src/helper/geom-nodetype.cpp
new file mode 100644
index 000000000..b43c30a8f
--- /dev/null
+++ b/src/helper/geom-nodetype.cpp
@@ -0,0 +1,74 @@
+#define INKSCAPE_HELPER_GEOM_NODETYPE_CPP
+
+/**
+ * Specific nodetype geometry functions for Inkscape, not provided my lib2geom.
+ *
+ * Author:
+ *   Johan Engelen <goejendaagh@zonnet.nl>
+ *
+ * Copyright (C) 2008 Johan Engelen
+ *
+ * Released under GNU GPL
+ */
+
+#include "helper/geom-nodetype.h"
+
+#include <2geom/curve.h>
+#include <2geom/point.h>
+#include <vector>
+
+namespace Geom {
+
+/*
+ * Returns the nodetype between c_incoming and c_outgoing. Location of the node is
+ * at c_incoming.pointAt(1) == c_outgoing.pointAt(0). If these two are unequal, 
+ * the returned type is NODE_NONE.
+ * This method uses exact floating point comparison, so the final and initial points of
+ * the two input curves should match exactly!
+ */
+NodeType get_nodetype(Curve const &c_incoming, Curve const &c_outgoing)
+{
+    // FIXME: this should be exact floating point match, not are_near!
+    if ( !are_near(c_incoming.pointAt(1), c_outgoing.pointAt(0)) )
+        return NODE_NONE;
+
+    Curve * c1_reverse = c_incoming.reverse();
+    std::vector<Point> deriv1 = c1_reverse->pointAndDerivatives(0, 3);
+    delete c1_reverse;
+    std::vector<Point> deriv2 = c_outgoing.pointAndDerivatives(0, 3);
+
+    // Determine lowest derivative that is non-zero
+    int n1 = 1;
+    while ( (deriv1[n1] == Point(0,0)) && (n1 < 3) ) {
+        n1++;
+    }
+    int n2 = 1;
+    while ( (deriv2[n2] == Point(0,0)) && (n2 < 3) ) {
+        n2++;
+    }
+
+    double const angle1 = Geom::atan2(-deriv1[n1]);
+    double const angle2 = Geom::atan2(deriv2[n2]);
+
+    if ( !are_near(angle1, angle2) )
+        return NODE_CUSP;   // derivatives are not colinear
+
+    // Apparently, the derivatives are colinear but does the order of the derivatives match?
+    if (n1 != n2)
+        return NODE_SMOOTH;
+    else
+        return NODE_SYMM;
+}
+
+}
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :
diff --git a/src/helper/geom-nodetype.h b/src/helper/geom-nodetype.h
new file mode 100644
index 000000000..932ba6d84
--- /dev/null
+++ b/src/helper/geom-nodetype.h
@@ -0,0 +1,54 @@
+#ifndef INKSCAPE_HELPER_GEOM_NODETYPE_H
+#define INKSCAPE_HELPER_GEOM_NODETYPE_H
+
+/**
+ * Specific nodetype geometry functions for Inkscape, not provided my lib2geom.
+ *
+ * Author:
+ *   Johan Engelen <goejendaagh@zonnet.nl>
+ *
+ * Copyright (C) 2008 Johan Engelen
+ *
+ * Released under GNU GPL
+ */
+
+#include <2geom/forward.h>
+
+namespace Geom {
+
+/**
+ *  What kind of node is this?  This is the value for the node->type
+ *  field.  NodeType indicates the degree of continuity required for
+ *  the node.  I think that the corresponding integer indicates which
+ *  derivate is connected. (Thus 2 means that the node is continuous
+ *  to the second derivative, i.e. has matching endpoints and tangents)
+ */
+typedef enum {
+/**  Discontinuous node, usually either start or endpoint of a path */
+    NODE_NONE,
+/**  This node continuously joins two segments, but the unit tangent is discontinuous.*/
+    NODE_CUSP,
+/**  This node continuously joins two segments, with continuous *unit* tangent. */
+    NODE_SMOOTH,
+/**  This node is symmetric. I.e. continously joins two segments with continuous derivative */
+    NODE_SYMM
+} NodeType;
+
+
+NodeType get_nodetype(Curve const &c_incoming, Curve const &c_outgoing);
+
+
+} // namespace Geom
+
+#endif  // INKSCAPE_HELPER_GEOM_NODETYPE_H
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :