From b91b26dfd424a46b90e69643dacd94feccff4731 Mon Sep 17 00:00:00 2001
From: cilix42 <cilix42@users.sourceforge.net>
Date: Mon, 19 May 2008 16:10:35 +0000
Subject: [PATCH] Add handles to adapt tangent length

---
 src/live_effects/lpe-tangent_to_curve.cpp | 48 +++++++++++++++++++++--
 src/live_effects/lpe-tangent_to_curve.h   | 12 +++++-
 2 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/src/live_effects/lpe-tangent_to_curve.cpp b/src/live_effects/lpe-tangent_to_curve.cpp
index e7344c9dc..92aca33c6 100644
--- a/src/live_effects/lpe-tangent_to_curve.cpp
+++ b/src/live_effects/lpe-tangent_to_curve.cpp
@@ -57,12 +57,52 @@ void attach_pt_set(SPItem *item, NR::Point const &p, NR::Point const &origin, gu
     sp_lpe_item_update_patheffect (SP_LPE_ITEM(item), true);
 }
 
+NR::Point left_end_get(SPItem *item) {
+    Inkscape::LivePathEffect::LPETangentToCurve *lpe =
+        (Inkscape::LivePathEffect::LPETangentToCurve *) sp_lpe_item_get_livepatheffect(SP_LPE_ITEM(item));
+
+    return lpe->C;
+}
+
+NR::Point right_end_get(SPItem *item) {
+    Inkscape::LivePathEffect::LPETangentToCurve *lpe =
+        (Inkscape::LivePathEffect::LPETangentToCurve *) sp_lpe_item_get_livepatheffect(SP_LPE_ITEM(item));
+
+    return lpe->D;
+}
+
+void left_end_set(SPItem *item, NR::Point const &p, NR::Point const &origin, guint state) {
+    Inkscape::LivePathEffect::LPETangentToCurve *lpe =
+        (Inkscape::LivePathEffect::LPETangentToCurve *) sp_lpe_item_get_livepatheffect(SP_LPE_ITEM(item));
+
+    double lambda = Geom::nearest_point(p.to_2geom(), lpe->ptA, lpe->derivA);
+    lpe->length_left.param_set_value(-lambda);
+
+    sp_lpe_item_update_patheffect (SP_LPE_ITEM(item), true);
+}
+
+void right_end_set(SPItem *item, NR::Point const &p, NR::Point const &origin, guint state) {
+    Inkscape::LivePathEffect::LPETangentToCurve *lpe =
+        (Inkscape::LivePathEffect::LPETangentToCurve *) sp_lpe_item_get_livepatheffect(SP_LPE_ITEM(item));
+
+    double lambda = Geom::nearest_point(p.to_2geom(), lpe->ptA, lpe->derivA);
+    lpe->length_right.param_set_value(lambda);
+
+    sp_lpe_item_update_patheffect (SP_LPE_ITEM(item), true);
+}
+
 LPETangentToCurve::LPETangentToCurve(LivePathEffectObject *lpeobject) :
     Effect(lpeobject),
-    t_attach(_("Location along curve"), _("Location of the point of attachment along the curve (between 0.0 and number-of-segments)"), "t_attach", &wr, this, 0.5)
+    t_attach(_("Location along curve"), _("Location of the point of attachment along the curve (between 0.0 and number-of-segments)"), "t_attach", &wr, this, 0.5),
+    length_left(_("Length left"), _("Specifies the left end of the tangent"), "length-left", &wr, this, 150),
+    length_right(_("Length right"), _("Specifies the right end of the tangent"), "length-right", &wr, this, 150)
 {
     registerParameter( dynamic_cast<Parameter *>(&t_attach) );
+    registerParameter( dynamic_cast<Parameter *>(&length_left) );
+    registerParameter( dynamic_cast<Parameter *>(&length_right) );
     registerKnotHolderHandle(attach_pt_set, attach_pt_get);
+    registerKnotHolderHandle(left_end_set, left_end_get);
+    registerKnotHolderHandle(right_end_set, right_end_get);
 }
 
 LPETangentToCurve::~LPETangentToCurve()
@@ -78,10 +118,10 @@ LPETangentToCurve::doEffect_pwd2 (Geom::Piecewise<Geom::D2<Geom::SBasis> > const
     ptA = pwd2_in.valueAt(t_attach);
     derivA = unit_vector(derivative(pwd2_in).valueAt(t_attach));
 
-    Point A = ptA - derivA * 100;
-    Point B = ptA + derivA * 100;
+    C = ptA - derivA * length_left;
+    D = ptA + derivA * length_right;
 
-    output = Piecewise<D2<SBasis> >(D2<SBasis>(Linear(A[X], B[X]), Linear(A[Y], B[Y])));
+    output = Piecewise<D2<SBasis> >(D2<SBasis>(Linear(C[X], D[X]), Linear(C[Y], D[Y])));
 
     return output;
 }
diff --git a/src/live_effects/lpe-tangent_to_curve.h b/src/live_effects/lpe-tangent_to_curve.h
index d8049c176..7d80b23bb 100644
--- a/src/live_effects/lpe-tangent_to_curve.h
+++ b/src/live_effects/lpe-tangent_to_curve.h
@@ -33,14 +33,24 @@ public:
 
     /* the knotholder functions must be declared friends */
     friend NR::Point attach_pt_get(SPItem *item);
+    friend NR::Point left_end_get(SPItem *item);
+    friend NR::Point right_end_get(SPItem *item);
     friend void attach_pt_set(SPItem *item, NR::Point const &p, NR::Point const &origin, guint state);
+    friend void left_end_set(SPItem *item, NR::Point const &p, NR::Point const &origin, guint state);
+    friend void right_end_set(SPItem *item, NR::Point const &p, NR::Point const &origin, guint state);
 
 private:
     ScalarParam t_attach;
 
-    Geom::Point ptA;
+    ScalarParam length_left;
+    ScalarParam length_right;
+
+    Geom::Point ptA; // point of attachment to the curve
     Geom::Point derivA;
 
+    Geom::Point C; // left end of tangent
+    Geom::Point D; // right end of tangent
+
     LPETangentToCurve(const LPETangentToCurve&);
     LPETangentToCurve& operator=(const LPETangentToCurve&);
 };
-- 
2.30.2