Add a constraint for tangency between any combination of arcs

and cubics. Also add that to the library interface.

It might have been better to use a single constraint for that,
plus all the line-curve or line-line cases, but it would break
backwards compatibility if I did that now, and perhaps be
confusing with the 'other' member (which is meaningless for
lines) anyways.

[git-p4: depot-paths = "//depot/solvespace/": change = 2141]

constraint.cpp

@@ -32,6 +32,7 @@ char *Constraint::DescriptionString(void) {
         case PARALLEL:              s = "parallel"; break;
         case ARC_LINE_TANGENT:      s = "arc-line-tangent"; break;
         case CUBIC_LINE_TANGENT:    s = "cubic-line-tangent"; break;
+        case CURVE_CURVE_TANGENT:   s = "curve-curve-tangent"; break;
         case PERPENDICULAR:         s = "perpendicular"; break;
         case EQUAL_RADIUS:          s = "eq-radius"; break;
         case EQUAL_ANGLE:           s = "eq-angle"; break;
@@ -616,16 +617,42 @@ void Constraint::MenuConstrain(int id) {
                 c.type = CUBIC_LINE_TANGENT;
                 c.entityA = cubic->h;
                 c.entityB = line->h;
+            } else if(gs.cubics + gs.arcs == 2 && gs.n == 2) {
+                if(!SS.GW.LockedInWorkplane()) {
+                    Error("Curve-curve tangency must apply in workplane.");
+                    return;
+                }
+                Entity *eA = SK.GetEntity(gs.entity[0]),
+                       *eB = SK.GetEntity(gs.entity[1]);
+                Vector as = eA->EndpointStart(),
+                       af = eA->EndpointFinish(),
+                       bs = eB->EndpointStart(),
+                       bf = eB->EndpointFinish();
+                if(as.Equals(bs)) {
+                    c.other = false; c.other2 = false;
+                } else if(as.Equals(bf)) {
+                    c.other = false; c.other2 = true;
+                } else if(af.Equals(bs)) {
+                    c.other = true; c.other2 = false;
+                } else if(af.Equals(bf)) {
+                    c.other = true; c.other2 = true;
+                } else {
+                    Error("The curves must share an endpoint. Constrain them "
+                          "with Constrain -> On Point before constraining "
+                          "tangent.");
+                    return;
+                }
+                c.type = CURVE_CURVE_TANGENT;
+                c.entityA = eA->h;
+                c.entityB = eB->h;
             } else {
                 Error("Bad selection for parallel / tangent constraint. This "
                       "constraint can apply to:\n\n"
                       "    * two line segments (parallel)\n"
                       "    * a line segment and a normal (parallel)\n"
                       "    * two normals (parallel)\n"
-                      "    * a line segment and an arc, that share an endpoint "
+                      "    * two line segments, arcs, or beziers, that share "
-                             "(tangent)\n"
+                            "an endpoint (tangent)\n");
-                      "    * a line segment and a cubic bezier, that share an "
-                             "endpoint (tangent)\n");
                 return;
             }
             AddConstraint(&c);

constrainteq.cpp

@@ -689,6 +689,44 @@ void ConstraintBase::GenerateReal(IdList<Equation,hEquation> *l) {
             break;
         }
 
+        case CURVE_CURVE_TANGENT: {
+            bool parallel = true;
+            int i;
+            ExprVector dir[2];
+            for(i = 0; i < 2; i++) {
+                EntityBase *e = SK.GetEntity((i == 0) ? entityA : entityB);
+                bool oth = (i == 0) ? other : other2;
+
+                if(e->type == Entity::ARC_OF_CIRCLE) {
+                    ExprVector center, endpoint;
+                    center = SK.GetEntity(e->point[0])->PointGetExprs();
+                    endpoint =
+                        SK.GetEntity(e->point[oth ? 2 : 1])->PointGetExprs();
+                    dir[i] = endpoint.Minus(center);
+                    // We're using the vector from the center of the arc to
+                    // an endpoint; so that's normal to the tangent, not
+                    // parallel.
+                    parallel = !parallel;
+                } else if(e->type == Entity::CUBIC) {
+                    if(oth) {
+                        dir[i] = e->CubicGetFinishTangentExprs();
+                    } else {
+                        dir[i] = e->CubicGetStartTangentExprs();
+                    }
+                } else {
+                    oops();
+                }
+            }
+            if(parallel) {
+                EntityBase *w = SK.GetEntity(workplane);
+                ExprVector wn = w->Normal()->NormalExprsN();
+                AddEq(l, ((dir[0]).Cross(dir[1])).Dot(wn), 0);
+            } else {
+                AddEq(l, (dir[0]).Dot(dir[1]), 0);
+            }
+            break;
+        }
+
         case PARALLEL: {
             EntityBase *ea = SK.GetEntity(entityA), *eb = SK.GetEntity(entityB);
             if(eb->group.v != group.v) {

drawconstraint.cpp

@@ -698,6 +698,7 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
             break;
         }
 
+        case CURVE_CURVE_TANGENT:
         case CUBIC_LINE_TANGENT:
         case ARC_LINE_TANGENT: {
             Vector textAt, u, v;
@@ -712,7 +713,7 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
                 textAt = p.Plus(r.WithMagnitude(14/SS.GW.scale));
                 u = norm->NormalU();
                 v = norm->NormalV();
-            } else {
+            } else if(type == CUBIC_LINE_TANGENT) {
                 Vector n;
                 if(workplane.v == Entity::FREE_IN_3D.v) {
                     u = gr;
@@ -731,6 +732,37 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
                 Vector dir = SK.GetEntity(entityB)->VectorGetNum();
                 Vector out = n.Cross(dir);
                 textAt = p.Plus(out.WithMagnitude(14/SS.GW.scale));
+            } else {
+                Vector n, dir;
+                EntityBase *wn = SK.GetEntity(workplane)->Normal();
+                u = wn->NormalU();
+                v = wn->NormalV();
+                n = wn->NormalN();
+                EntityBase *eA = SK.GetEntity(entityA);
+                // Big pain; we have to get a vector tangent to the curve
+                // at the shared point, which could be from either a cubic
+                // or an arc.
+                if(other) {
+                    textAt = eA->EndpointFinish();
+                    if(eA->type == Entity::CUBIC) {
+                        dir = eA->CubicGetFinishTangentNum();
+                    } else {
+                        dir = SK.GetEntity(eA->point[0])->PointGetNum().Minus(
+                              SK.GetEntity(eA->point[2])->PointGetNum());
+                        dir = n.Cross(dir);
+                    }
+                } else {
+                    textAt = eA->EndpointStart();
+                    if(eA->type == Entity::CUBIC) {
+                        dir = eA->CubicGetStartTangentNum();
+                    } else {
+                        dir = SK.GetEntity(eA->point[0])->PointGetNum().Minus(
+                              SK.GetEntity(eA->point[1])->PointGetNum());
+                        dir = n.Cross(dir);
+                    }
+                }
+                dir = n.Cross(dir);
+                textAt = textAt.Plus(dir.WithMagnitude(14/SS.GW.scale));
             }
 
             if(dogd.drawing) {

entity.cpp

@@ -130,6 +130,16 @@ ExprVector EntityBase::CubicGetFinishTangentExprs(void) {
                poff = SK.GetEntity(point[2+extraPoints])->PointGetExprs();
     return (pon.Minus(poff));
 }
+Vector EntityBase::CubicGetStartTangentNum(void) {
+    Vector pon  = SK.GetEntity(point[0])->PointGetNum(),
+           poff = SK.GetEntity(point[1])->PointGetNum();
+    return (pon.Minus(poff));
+}
+Vector EntityBase::CubicGetFinishTangentNum(void) {
+    Vector pon  = SK.GetEntity(point[3+extraPoints])->PointGetNum(),
+           poff = SK.GetEntity(point[2+extraPoints])->PointGetNum();
+    return (pon.Minus(poff));
+}
 
 bool EntityBase::IsWorkplane(void) {
     return (type == WORKPLANE);

exposed/DOC.txt

@@ -414,9 +414,26 @@ SLVS_C_ARC_LINE_TANGENT**
 
 SLVS_C_CUBIC_LINE_TANGENT*
 
-    The cubic entityA is tangent to the line entityB. If other is false,
+    The cubic entityA is tangent to the line entityB. The variable
-    then the cubic is tangent at its beginning (point[0]). If other is
+    other indicates:
-    true, then the arc is tangent at its end (point[3]).
+
+        if false: the cubic is tangent at its beginning
+        if true:  the cubic is tangent at its end
+
+    The beginning of the cubic is point[0], and the end is point[3].
+
+SLVS_C_CURVE_CURVE_TANGENT**
+
+    The two entities entityA and entityB are tangent. These entities can
+    each be either an arc or a cubic, in any combination. The flags
+    other and other2 indicate which endpoint of the curve is tangent,
+    for entityA and entityB respectively:
+
+        if false: the entity is tangent at its beginning
+        if true:  the entity is tangent at its end
+
+    For cubics, point[0] is the beginning, and point[3] is the end. For
+    arcs, point[1] is the beginning, and point[2] is the end.
 
 SLVS_C_EQUAL_RADIUS
 

exposed/lib.cpp

@@ -166,6 +166,7 @@ case SLVS_C_CUBIC_LINE_TANGENT: t = Constraint::CUBIC_LINE_TANGENT; break;
 case SLVS_C_EQUAL_RADIUS:       t = Constraint::EQUAL_RADIUS; break;
 case SLVS_C_PROJ_PT_DISTANCE:   t = Constraint::PROJ_PT_DISTANCE; break;
 case SLVS_C_WHERE_DRAGGED:      t = Constraint::WHERE_DRAGGED; break;
+case SLVS_C_CURVE_CURVE_TANGENT:t = Constraint::CURVE_CURVE_TANGENT; break;
 
 default: dbp("bad constraint type %d", sc->type); return;
         }
@@ -183,6 +184,7 @@ default: dbp("bad constraint type %d", sc->type); return;
         c.entityC.v     = sc->entityC;
         c.entityD.v     = sc->entityD;
         c.other         = (sc->other) ? true : false;
+        c.other2        = (sc->other2) ? true : false;
 
         SK.constraint.Add(&c);
     }

exposed/slvs.h

@@ -100,6 +100,7 @@ typedef struct {
 #define SLVS_C_EQUAL_RADIUS             100029
 #define SLVS_C_PROJ_PT_DISTANCE         100030
 #define SLVS_C_WHERE_DRAGGED            100031
+#define SLVS_C_CURVE_CURVE_TANGENT      100032
 
 typedef struct {
     Slvs_hConstraint    h;
@@ -118,6 +119,7 @@ typedef struct {
     Slvs_hEntity        entityD;
     
     int                 other;
+    int                 other2;
 } Slvs_Constraint;
 
 

file.cpp

@@ -171,6 +171,7 @@ const SolveSpace::SaveTable SolveSpace::SAVED[] = {
     { 'c',  "Constraint.entityC.v",     'x',    &(SS.sv.c.entityC.v)          },
     { 'c',  "Constraint.entityD.v",     'x',    &(SS.sv.c.entityD.v)          },
     { 'c',  "Constraint.other",         'b',    &(SS.sv.c.other)              },
+    { 'c',  "Constraint.other2",        'b',    &(SS.sv.c.other2)             },
     { 'c',  "Constraint.reference",     'b',    &(SS.sv.c.reference)          },
     { 'c',  "Constraint.comment",       'N',    &(SS.sv.c.comment)            },
     { 'c',  "Constraint.disp.offset.x", 'f',    &(SS.sv.c.disp.offset.x)      },

sketch.h

@@ -399,6 +399,8 @@ public:
     Vector CubicGetFinishNum(void);
     ExprVector CubicGetStartTangentExprs(void);
     ExprVector CubicGetFinishTangentExprs(void);
+    Vector CubicGetStartTangentNum(void);
+    Vector CubicGetFinishTangentNum(void);
 
     bool HasEndpoints(void);
     Vector EndpointStart();
@@ -539,6 +541,7 @@ public:
     static const int PERPENDICULAR          = 122;
     static const int ARC_LINE_TANGENT       = 123;
     static const int CUBIC_LINE_TANGENT     = 124;
+    static const int CURVE_CURVE_TANGENT    = 125;
     static const int EQUAL_RADIUS           = 130;
     static const int WHERE_DRAGGED          = 200;
 
@@ -558,6 +561,7 @@ public:
     hEntity     entityC;
     hEntity     entityD;
     bool        other;
+    bool        other2;
 
     bool        reference;  // a ref dimension, that generates no eqs
     NameStr     comment;    // since comments are represented as constraints

wishlist.txt

@@ -1,5 +1,5 @@
 fix bug with rotation in plane where green line stays displayed
-more tangencies, and rounding (of requests, not parametric)
+rounding (of requests, not parametric)
 
 -----
 rounding, as a special group