New LPE: Offset

(bzr r6126)

1 files changed, 95 insertions, 0 deletions

diff --git a/src/live_effects/lpe-offset.cpp b/src/live_effects/lpe-offset.cpp
new file mode 100644
index 000000000..2916b9fa2
--- /dev/null
+++ b/src/live_effects/lpe-offset.cpp
@@ -0,0 +1,95 @@
+#define INKSCAPE_LPE_OFFSET_CPP
+/** \file
+ * LPE <offset> implementation
+ */
+/*
+ * Authors:
+ *   Maximilian Albert
+ *
+ * Copyright (C) Johan Engelen 2007 <j.b.c.engelen@utwente.nl>
+ * Copyright (C) Maximilian Albert 2008 <maximilian.albert@gmail.com>
+ *
+ * Released under GNU GPL, read the file 'COPYING' for more information
+ */
+
+#include "live_effects/lpe-offset.h"
+#include "sp-shape.h"
+#include "display/curve.h"
+
+#include <2geom/path.h>
+#include <2geom/piecewise.h>
+#include <2geom/sbasis-geometric.h>
+#include <2geom/elliptical-arc.h>
+#include <2geom/transforms.h>
+
+namespace Inkscape {
+namespace LivePathEffect {
+
+LPEOffset::LPEOffset(LivePathEffectObject *lpeobject) :
+    Effect(lpeobject),
+    offset_pt(_("Offset"), _("Handle to control the distance of the offset from the curve"), "offset_pt", &wr, this)
+{
+    show_orig_path = true;
+
+    registerParameter(dynamic_cast<Parameter *>(&offset_pt));
+}
+
+LPEOffset::~LPEOffset()
+{
+}
+
+void
+LPEOffset::doOnApply(SPLPEItem *lpeitem)
+{
+    offset_pt.param_set_and_write_new_value(SP_SHAPE(lpeitem)->curve->first_point().to_2geom());
+}
+
+static void append_half_circle(Geom::Piecewise<Geom::D2<Geom::SBasis> > &pwd2,
+                               Geom::Point const center, Geom::Point const &dir) {
+    using namespace Geom;
+
+    double r = L2(dir);
+    EllipticalArc cap(center + dir, r, r, angle_between(Point(1,0), dir), false, false, center - dir);
+    Piecewise<D2<SBasis> > cap_pwd2(cap.toSBasis());
+    pwd2.continuousConcat(cap_pwd2);
+}
+
+Geom::Piecewise<Geom::D2<Geom::SBasis> >
+LPEOffset::doEffect_pwd2 (Geom::Piecewise<Geom::D2<Geom::SBasis> > const & pwd2_in)
+{
+    using namespace Geom;
+
+    Piecewise<D2<SBasis> > output;
+
+    double t = nearest_point(offset_pt, pwd2_in);
+    Point A = pwd2_in.valueAt(t);
+    double offset = L2(A - offset_pt);
+
+    Piecewise<D2<SBasis> > der = unitVector(derivative(pwd2_in));
+    Piecewise<D2<SBasis> > n   = rot90(der);
+
+    output  = pwd2_in + n * offset;
+    append_half_circle(output, pwd2_in.lastValue(), n.lastValue() * offset);
+    output.continuousConcat(reverse(pwd2_in - n * offset));
+    append_half_circle(output, pwd2_in.firstValue(), -n.firstValue() * offset);
+
+    // TODO: here we should remove self-overlaps by applying the "union" boolop
+    //       but we'd need to convert the path to a Shape, which is currently
+    //       broken in 2geom, so we return the unaltered path
+
+    return output;
+}
+
+} //namespace LivePathEffect
+} /* namespace Inkscape */
+
+/*
+  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 :