//-----------------------------------------------------------------------------
// A curve by its parametric equation, helper functions for computing tangent
// arcs by a numerical method.
//-----------------------------------------------------------------------------
void GraphicsWindow::ParametricCurve::MakeFromEntity(hEntity he, bool reverse) {
    ZERO(this);
    Entity *e = SK.GetEntity(he);
    if(e->type == Entity::LINE_SEGMENT) {
        isLine = true;
        p0 = e->EndpointStart(),
        p1 = e->EndpointFinish();
        if(reverse) {
            SWAP(Vector, p0, p1);
        }
    } else if(e->type == Entity::ARC_OF_CIRCLE) {
        isLine = false;
        p0 = SK.GetEntity(e->point[0])->PointGetNum();
        Vector pe = SK.GetEntity(e->point[1])->PointGetNum();
        r = (pe.Minus(p0)).Magnitude();
        e->ArcGetAngles(&theta0, &theta1, &dtheta);
        if(reverse) {
            SWAP(double, theta0, theta1);
            dtheta = -dtheta;
        }
        EntityBase *wrkpln = SK.GetEntity(e->workplane)->Normal();
        u = wrkpln->NormalU();
        v = wrkpln->NormalV();
    } else {
        oops();
    }
}
void Constraint::DrawOrGetDistance(Vector *labelPos) {
    if(!SS.GW.showConstraints) return;
    Group *g = SK.GetGroup(group);
    // If the group is hidden, then the constraints are hidden and not
    // able to be selected.
    if(!(g->visible)) return;
    // And likewise if the group is not the active group; except for comments
    // with an assigned style.
    if(g->h.v != SS.GW.activeGroup.v && !(type == COMMENT && disp.style.v)) {
        return;
    }
    if(disp.style.v) {
        Style *s = Style::Get(disp.style);
        if(!s->visible) return;
    }

    // Unit vectors that describe our current view of the scene. One pixel
    // long, not one actual unit.
    Vector gr = SS.GW.projRight.ScaledBy(1/SS.GW.scale);
    Vector gu = SS.GW.projUp.ScaledBy(1/SS.GW.scale);
    Vector gn = (gr.Cross(gu)).WithMagnitude(1/SS.GW.scale);

    switch(type) {
        case PT_PT_DISTANCE: {
            Vector ap = SK.GetEntity(ptA)->PointGetNum();
            Vector bp = SK.GetEntity(ptB)->PointGetNum();

            if(workplane.v != Entity::FREE_IN_3D.v) {
                DoProjectedPoint(&ap);
                DoProjectedPoint(&bp);
            }

            Vector ref = ((ap.Plus(bp)).ScaledBy(0.5)).Plus(disp.offset);

            DoLineWithArrows(ref, ap, bp, false);
            DoLabel(ref, labelPos, gr, gu);
            break;
        }

        case PROJ_PT_DISTANCE: {
            Vector ap = SK.GetEntity(ptA)->PointGetNum(),
                   bp = SK.GetEntity(ptB)->PointGetNum(),
                   dp = (bp.Minus(ap)),
                   pp = SK.GetEntity(entityA)->VectorGetNum();

            Vector ref = ((ap.Plus(bp)).ScaledBy(0.5)).Plus(disp.offset);

            pp = pp.WithMagnitude(1);
            double d = dp.Dot(pp);
            Vector bpp = ap.Plus(pp.ScaledBy(d));
            StippledLine(ap, bpp);
            StippledLine(bp, bpp);

            DoLineWithArrows(ref, ap, bpp, false);
            DoLabel(ref, labelPos, gr, gu);
            break;
        }

        case PT_FACE_DISTANCE:
        case PT_PLANE_DISTANCE: {
            Vector pt = SK.GetEntity(ptA)->PointGetNum();
            Entity *enta = SK.GetEntity(entityA);
            Vector n, p;
            if(type == PT_PLANE_DISTANCE) {
                n = enta->Normal()->NormalN();
                p = enta->WorkplaneGetOffset();
            } else {
                n = enta->FaceGetNormalNum();
                p = enta->FaceGetPointNum();
            }

            double d = (p.Minus(pt)).Dot(n);
            Vector closest = pt.Plus(n.WithMagnitude(d));

            Vector ref = ((closest.Plus(pt)).ScaledBy(0.5)).Plus(disp.offset);

            if(!pt.Equals(closest)) {
                DoLineWithArrows(ref, pt, closest, true);
            }

            DoLabel(ref, labelPos, gr, gu);
            break;
        }

        case PT_LINE_DISTANCE: {
            Vector pt = SK.GetEntity(ptA)->PointGetNum();
            Entity *line = SK.GetEntity(entityA);
            Vector lA = SK.GetEntity(line->point[0])->PointGetNum();
            Vector lB = SK.GetEntity(line->point[1])->PointGetNum();
            Vector dl = lB.Minus(lA);

            if(workplane.v != Entity::FREE_IN_3D.v) {
                lA = lA.ProjectInto(workplane);
                lB = lB.ProjectInto(workplane);
                DoProjectedPoint(&pt);
            }

            // Find the closest point on the line
            Vector closest = pt.ClosestPointOnLine(lA, dl);

            Vector ref = ((closest.Plus(pt)).ScaledBy(0.5)).Plus(disp.offset);
            DoLabel(ref, labelPos, gr, gu);

            if(!pt.Equals(closest)) {
                DoLineWithArrows(ref, pt, closest, true);
            }

            if(workplane.v != Entity::FREE_IN_3D.v) {
                // Draw the projection marker from the closest point on the
                // projected line to the projected point on the real line.
                Vector lAB = (lA.Minus(lB));
                double t = (lA.Minus(closest)).DivPivoting(lAB);

                Vector lA = SK.GetEntity(line->point[0])->PointGetNum();
                Vector lB = SK.GetEntity(line->point[1])->PointGetNum();

                Vector c2 = (lA.ScaledBy(1-t)).Plus(lB.ScaledBy(t));
                DoProjectedPoint(&c2);
            }
            break;
        }

        case DIAMETER: {
            Entity *circle = SK.GetEntity(entityA);
            Vector center = SK.GetEntity(circle->point[0])->PointGetNum();
            Quaternion q = SK.GetEntity(circle->normal)->NormalGetNum();
            Vector n = q.RotationN().WithMagnitude(1);
            double r = circle->CircleGetRadiusNum();

            Vector ref = center.Plus(disp.offset);
            // Force the label into the same plane as the circle.
            ref = ref.Minus(n.ScaledBy(n.Dot(ref) - n.Dot(center)));

            Vector mark = ref.Minus(center);
            mark = mark.WithMagnitude(mark.Magnitude()-r);
            DoLineTrimmedAgainstBox(ref, ref, ref.Minus(mark));

            Vector topLeft;
            DoLabel(ref, &topLeft, gr, gu);
            if(labelPos) *labelPos = topLeft;

            // Show this as diameter or radius?
            if(!other) {
                // Draw the diameter symbol
                Vector dc = topLeft;
                dc = dc.Plus(gu.WithMagnitude(5/SS.GW.scale));
                dc = dc.Plus(gr.WithMagnitude(9/SS.GW.scale));
                double dr = 5/SS.GW.scale;
                double theta, dtheta = (2*PI)/12;
                for(theta = 0; theta < 2*PI-0.01; theta += dtheta) {
                    LineDrawOrGetDistance(
                        dc.Plus(gu.WithMagnitude(cos(theta)*dr)).Plus(
                                gr.WithMagnitude(sin(theta)*dr)),
                        dc.Plus(gu.WithMagnitude(cos(theta+dtheta)*dr)).Plus(
                                gr.WithMagnitude(sin(theta+dtheta)*dr)));
                }
                theta = 25*(PI/180);
                dr *= 1.7;
                dtheta = PI;
                LineDrawOrGetDistance(
                    dc.Plus(gu.WithMagnitude(cos(theta)*dr)).Plus(
                            gr.WithMagnitude(sin(theta)*dr)),
                    dc.Plus(gu.WithMagnitude(cos(theta+dtheta)*dr)).Plus(
                            gr.WithMagnitude(sin(theta+dtheta)*dr)));
            }
            break;
        }

        case POINTS_COINCIDENT: {
            if(!dogd.drawing) {
                for(int i = 0; i < 2; i++) {
                    Vector p = SK.GetEntity(i == 0 ? ptA : ptB)-> PointGetNum();
                    Point2d pp = SS.GW.ProjectPoint(p);
                    // The point is selected within a radius of 7, from the
                    // same center; so if the point is visible, then this
                    // constraint cannot be selected. But that's okay.
                    dogd.dmin = min(dogd.dmin, pp.DistanceTo(dogd.mp) - 3);
                    dogd.refp = p;
                }
                break;
            }

            if(dogd.drawing) {
                // Let's adjust the color of this constraint to have the same
                // rough luma as the point color, so that the constraint does not
                // stand out in an ugly way.
                RgbaColor cd = Style::Color(Style::DATUM),
                         cc = Style::Color(Style::CONSTRAINT);
                // convert from 8-bit color to a vector
                Vector vd = Vector::From(cd.redF(), cd.greenF(), cd.blueF()),
                       vc = Vector::From(cc.redF(), cc.greenF(), cc.blueF());
                // and scale the constraint color to have the same magnitude as
                // the datum color, maybe a bit dimmer
                vc = vc.WithMagnitude(vd.Magnitude()*0.9);
                // and set the color to that.
                ssglColorRGB(RGBf(vc.x, vc.y, vc.z));

                for(int a = 0; a < 2; a++) {
                    Vector r = SS.GW.projRight.ScaledBy((a+1)/SS.GW.scale);
                    Vector d = SS.GW.projUp.ScaledBy((2-a)/SS.GW.scale);
                    for(int i = 0; i < 2; i++) {
                        Vector p = SK.GetEntity(i == 0 ? ptA : ptB)-> PointGetNum();
                        glBegin(GL_QUADS);
                            ssglVertex3v(p.Plus (r).Plus (d));
                            ssglVertex3v(p.Plus (r).Minus(d));
                            ssglVertex3v(p.Minus(r).Minus(d));
                            ssglVertex3v(p.Minus(r).Plus (d));
                        glEnd();
                    }

                }
            }
            break;
        }

        case PT_ON_CIRCLE:
        case PT_ON_LINE:
        case PT_ON_FACE:
        case PT_IN_PLANE: {
            double s = 8/SS.GW.scale;
            Vector p = SK.GetEntity(ptA)->PointGetNum();
            Vector r, d;
            if(type == PT_ON_FACE) {
                Vector n = SK.GetEntity(entityA)->FaceGetNormalNum();
                r = n.Normal(0);
                d = n.Normal(1);
            } else if(type == PT_IN_PLANE) {
                EntityBase *n = SK.GetEntity(entityA)->Normal();
                r = n->NormalU();
                d = n->NormalV();
            } else {
                r = gr;
                d = gu;
                s *= (6.0/8); // draw these a little smaller
            }
            r = r.WithMagnitude(s); d = d.WithMagnitude(s);
            LineDrawOrGetDistance(p.Plus (r).Plus (d), p.Plus (r).Minus(d));
            LineDrawOrGetDistance(p.Plus (r).Minus(d), p.Minus(r).Minus(d));
            LineDrawOrGetDistance(p.Minus(r).Minus(d), p.Minus(r).Plus (d));
            LineDrawOrGetDistance(p.Minus(r).Plus (d), p.Plus (r).Plus (d));
            break;
        }

        case WHERE_DRAGGED: {
            Vector p = SK.GetEntity(ptA)->PointGetNum(),
                   u = p.Plus(gu.WithMagnitude(8/SS.GW.scale)).Plus(
                              gr.WithMagnitude(8/SS.GW.scale)),
                   uu = u.Minus(gu.WithMagnitude(5/SS.GW.scale)),
                   ur = u.Minus(gr.WithMagnitude(5/SS.GW.scale));
            // Draw four little crop marks, uniformly spaced (by ninety
            // degree rotations) around the point.
            int i;
            for(i = 0; i < 4; i++) {
                LineDrawOrGetDistance(u, uu);
                LineDrawOrGetDistance(u, ur);
                u = u.RotatedAbout(p, gn, PI/2);
                ur = ur.RotatedAbout(p, gn, PI/2);
                uu = uu.RotatedAbout(p, gn, PI/2);
            }
            break;
        }

        case SAME_ORIENTATION: {
            for(int i = 0; i < 2; i++) {
                Entity *e = SK.GetEntity(i == 0 ? entityA : entityB);
                Quaternion q = e->NormalGetNum();
                Vector n = q.RotationN().WithMagnitude(25/SS.GW.scale);
                Vector u = q.RotationU().WithMagnitude(6/SS.GW.scale);
                Vector p = SK.GetEntity(e->point[0])->PointGetNum();
                p = p.Plus(n.WithMagnitude(10/SS.GW.scale));

                LineDrawOrGetDistance(p.Plus(u), p.Minus(u).Plus(n));
                LineDrawOrGetDistance(p.Minus(u), p.Plus(u).Plus(n));
            }
            break;
        }

        case EQUAL_ANGLE: {
            Vector ref;
            Entity *a = SK.GetEntity(entityA);
            Entity *b = SK.GetEntity(entityB);
            Entity *c = SK.GetEntity(entityC);
            Entity *d = SK.GetEntity(entityD);

            Vector a0 = a->VectorGetRefPoint();
            Vector b0 = b->VectorGetRefPoint();
            Vector c0 = c->VectorGetRefPoint();
            Vector d0 = d->VectorGetRefPoint();
            Vector da = a->VectorGetNum();
            Vector db = b->VectorGetNum();
            Vector dc = c->VectorGetNum();
            Vector dd = d->VectorGetNum();

            if(other) da = da.ScaledBy(-1);

            DoArcForAngle(a0, da, b0, db,
                da.WithMagnitude(40/SS.GW.scale), &ref);
            DoArcForAngle(c0, dc, d0, dd,
                dc.WithMagnitude(40/SS.GW.scale), &ref);

            break;
        }

        case ANGLE: {
            Entity *a = SK.GetEntity(entityA);
            Entity *b = SK.GetEntity(entityB);

            Vector a0 = a->VectorGetRefPoint();
            Vector b0 = b->VectorGetRefPoint();
            Vector da = a->VectorGetNum();
            Vector db = b->VectorGetNum();
            if(other) da = da.ScaledBy(-1);

            Vector ref;
            DoArcForAngle(a0, da, b0, db, disp.offset, &ref);
            DoLabel(ref, labelPos, gr, gu);
            break;
        }

        case PERPENDICULAR: {
            Vector u = Vector::From(0, 0, 0), v = Vector::From(0, 0, 0);
            Vector rn, ru;
            if(workplane.v == Entity::FREE_IN_3D.v) {
                rn = gn;
                ru = gu;
            } else {
                EntityBase *normal = SK.GetEntity(workplane)->Normal();
                rn = normal->NormalN();
                ru = normal->NormalV(); // ru meaning r_up, not u/v
            }

            for(int i = 0; i < 2; i++) {
                Entity *e = SK.GetEntity(i == 0 ? entityA : entityB);

                if(i == 0) {
                    // Calculate orientation of perpendicular sign only
                    // once, so that it's the same both times it's drawn
                    u = e->VectorGetNum();
                    u = u.WithMagnitude(16/SS.GW.scale);
                    v = (rn.Cross(u)).WithMagnitude(16/SS.GW.scale);
                    // a bit of bias to stop it from flickering between the
                    // two possibilities
                    if(fabs(u.Dot(ru)) < fabs(v.Dot(ru)) + LENGTH_EPS) {
                        SWAP(Vector, u, v);
                    }
                    if(u.Dot(ru) < 0) u = u.ScaledBy(-1);
                }

                Vector p = e->VectorGetRefPoint();
                Vector s = p.Plus(u).Plus(v);
                LineDrawOrGetDistance(s, s.Plus(v));

                Vector m = s.Plus(v.ScaledBy(0.5));
                LineDrawOrGetDistance(m, m.Plus(u));
            }
            break;
        }

        case CURVE_CURVE_TANGENT:
        case CUBIC_LINE_TANGENT:
        case ARC_LINE_TANGENT: {
            Vector textAt, u, v;

            if(type == ARC_LINE_TANGENT) {
                Entity *arc = SK.GetEntity(entityA);
                Entity *norm = SK.GetEntity(arc->normal);
                Vector c = SK.GetEntity(arc->point[0])->PointGetNum();
                Vector p =
                    SK.GetEntity(arc->point[other ? 2 : 1])->PointGetNum();
                Vector r = p.Minus(c);
                textAt = p.Plus(r.WithMagnitude(14/SS.GW.scale));
                u = norm->NormalU();
                v = norm->NormalV();
            } else if(type == CUBIC_LINE_TANGENT) {
                Vector n;
                if(workplane.v == Entity::FREE_IN_3D.v) {
                    u = gr;
                    v = gu;
                    n = gn;
                } else {
                    EntityBase *wn = SK.GetEntity(workplane)->Normal();
                    u = wn->NormalU();
                    v = wn->NormalV();
                    n = wn->NormalN();
                }

                Entity *cubic = SK.GetEntity(entityA);
                Vector p = other ? cubic->CubicGetFinishNum() :
                                   cubic->CubicGetStartNum();
                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) {
                ssglWriteTextRefCenter("T", DEFAULT_TEXT_HEIGHT,
                    textAt, u, v, LineCallback, this);
            } else {
                dogd.refp = textAt;
                Point2d ref = SS.GW.ProjectPoint(dogd.refp);
                dogd.dmin = min(dogd.dmin, ref.DistanceTo(dogd.mp)-10);
            }
            break;
        }

        case PARALLEL: {
            for(int i = 0; i < 2; i++) {
                Entity *e = SK.GetEntity(i == 0 ? entityA : entityB);
                Vector n = e->VectorGetNum();
                n = n.WithMagnitude(25/SS.GW.scale);
                Vector u = (gn.Cross(n)).WithMagnitude(4/SS.GW.scale);
                Vector p = e->VectorGetRefPoint();

                LineDrawOrGetDistance(p.Plus(u), p.Plus(u).Plus(n));
                LineDrawOrGetDistance(p.Minus(u), p.Minus(u).Plus(n));
            }
            break;
        }

        case EQUAL_RADIUS: {
            for(int i = 0; i < 2; i++) {
                DoEqualRadiusTicks(i == 0 ? entityA : entityB);
            }
            break;
        }

        case EQUAL_LINE_ARC_LEN: {
            Entity *line = SK.GetEntity(entityA);
            DoEqualLenTicks(
                SK.GetEntity(line->point[0])->PointGetNum(),
                SK.GetEntity(line->point[1])->PointGetNum(),
                gn);

            DoEqualRadiusTicks(entityB);
            break;
        }

        case LENGTH_RATIO:
        case EQUAL_LENGTH_LINES: {
            Vector a, b = Vector::From(0, 0, 0);
            for(int i = 0; i < 2; i++) {
                Entity *e = SK.GetEntity(i == 0 ? entityA : entityB);
                a = SK.GetEntity(e->point[0])->PointGetNum();
                b = SK.GetEntity(e->point[1])->PointGetNum();

                if(workplane.v != Entity::FREE_IN_3D.v) {
                    DoProjectedPoint(&a);
                    DoProjectedPoint(&b);
                }

                DoEqualLenTicks(a, b, gn);
            }
            if(type == LENGTH_RATIO) {
                Vector ref = ((a.Plus(b)).ScaledBy(0.5)).Plus(disp.offset);
                DoLabel(ref, labelPos, gr, gu);
            }
            break;
        }

        case EQ_LEN_PT_LINE_D: {
            Entity *forLen = SK.GetEntity(entityA);
            Vector a = SK.GetEntity(forLen->point[0])->PointGetNum(),
                   b = SK.GetEntity(forLen->point[1])->PointGetNum();
            if(workplane.v != Entity::FREE_IN_3D.v) {
                DoProjectedPoint(&a);
                DoProjectedPoint(&b);
            }
            DoEqualLenTicks(a, b, gn);

            Entity *ln = SK.GetEntity(entityB);
            Vector la = SK.GetEntity(ln->point[0])->PointGetNum(),
                   lb = SK.GetEntity(ln->point[1])->PointGetNum();
            Vector pt = SK.GetEntity(ptA)->PointGetNum();
            if(workplane.v != Entity::FREE_IN_3D.v) {
                DoProjectedPoint(&pt);
                la = la.ProjectInto(workplane);
                lb = lb.ProjectInto(workplane);
            }

            Vector closest = pt.ClosestPointOnLine(la, lb.Minus(la));
            LineDrawOrGetDistance(pt, closest);
            DoEqualLenTicks(pt, closest, gn);
            break;
        }

        case EQ_PT_LN_DISTANCES: {
            for(int i = 0; i < 2; i++) {
                Entity *ln = SK.GetEntity(i == 0 ? entityA : entityB);
                Vector la = SK.GetEntity(ln->point[0])->PointGetNum(),
                       lb = SK.GetEntity(ln->point[1])->PointGetNum();
                Entity *pte = SK.GetEntity(i == 0 ? ptA : ptB);
                Vector pt = pte->PointGetNum();

                if(workplane.v != Entity::FREE_IN_3D.v) {
                    DoProjectedPoint(&pt);
                    la = la.ProjectInto(workplane);
                    lb = lb.ProjectInto(workplane);
                }

                Vector closest = pt.ClosestPointOnLine(la, lb.Minus(la));

                LineDrawOrGetDistance(pt, closest);
                DoEqualLenTicks(pt, closest, gn);
            }
            break;
        }

        {
        case SYMMETRIC:
            Vector n;
            n = SK.GetEntity(entityA)->Normal()->NormalN(); goto s;
        case SYMMETRIC_HORIZ:
            n = SK.GetEntity(workplane)->Normal()->NormalU(); goto s;
        case SYMMETRIC_VERT:
            n = SK.GetEntity(workplane)->Normal()->NormalV(); goto s;
        case SYMMETRIC_LINE: {
            Entity *ln = SK.GetEntity(entityA);
            Vector la = SK.GetEntity(ln->point[0])->PointGetNum(),
                   lb = SK.GetEntity(ln->point[1])->PointGetNum();
            la = la.ProjectInto(workplane);
            lb = lb.ProjectInto(workplane);
            n = lb.Minus(la);
            Vector nw = SK.GetEntity(workplane)->Normal()->NormalN();
            n = n.RotatedAbout(nw, PI/2);
            goto s;
        }
s:
            Vector a = SK.GetEntity(ptA)->PointGetNum();
            Vector b = SK.GetEntity(ptB)->PointGetNum();

            for(int i = 0; i < 2; i++) {
                Vector tail = (i == 0) ? a : b;
                Vector d = (i == 0) ? b : a;
                d = d.Minus(tail);
                // Project the direction in which the arrow is drawn normal
                // to the symmetry plane; for projected symmetry constraints,
                // they might not be in the same direction, even when the
                // constraint is fully solved.
                d = n.ScaledBy(d.Dot(n));
                d = d.WithMagnitude(20/SS.GW.scale);
                Vector tip = tail.Plus(d);

                LineDrawOrGetDistance(tail, tip);
                d = d.WithMagnitude(9/SS.GW.scale);
                LineDrawOrGetDistance(tip, tip.Minus(d.RotatedAbout(gn,  0.6)));
                LineDrawOrGetDistance(tip, tip.Minus(d.RotatedAbout(gn, -0.6)));
            }
            break;
        }

        case AT_MIDPOINT:
        case HORIZONTAL:
        case VERTICAL:
            if(entityA.v) {
                Vector r, u, n;
                if(workplane.v == Entity::FREE_IN_3D.v) {
                    r = gr; u = gu; n = gn;
                } else {
                    r = SK.GetEntity(workplane)->Normal()->NormalU();
                    u = SK.GetEntity(workplane)->Normal()->NormalV();
                    n = r.Cross(u);
                }
                // For "at midpoint", this branch is always taken.
                Entity *e = SK.GetEntity(entityA);
                Vector a = SK.GetEntity(e->point[0])->PointGetNum();
                Vector b = SK.GetEntity(e->point[1])->PointGetNum();
                Vector m = (a.ScaledBy(0.5)).Plus(b.ScaledBy(0.5));
                Vector offset = (a.Minus(b)).Cross(n);
                offset = offset.WithMagnitude(13/SS.GW.scale);
                // Draw midpoint constraint on other side of line, so that
                // a line can be midpoint and horizontal at same time.
                if(type == AT_MIDPOINT) offset = offset.ScaledBy(-1);

                if(dogd.drawing) {
                    const char *s = (type == HORIZONTAL)  ? "H" : (
                                    (type == VERTICAL)    ? "V" : (
                                    (type == AT_MIDPOINT) ? "M" : NULL));

                    ssglWriteTextRefCenter(s, DEFAULT_TEXT_HEIGHT,
                        m.Plus(offset), r, u, LineCallback, this);
                } else {
                    dogd.refp = m.Plus(offset);
                    Point2d ref = SS.GW.ProjectPoint(dogd.refp);
                    dogd.dmin = min(dogd.dmin, ref.DistanceTo(dogd.mp)-10);
                }
            } else {
                Vector a = SK.GetEntity(ptA)->PointGetNum();
                Vector b = SK.GetEntity(ptB)->PointGetNum();

                Entity *w = SK.GetEntity(workplane);
                Vector cu = w->Normal()->NormalU();
                Vector cv = w->Normal()->NormalV();
                Vector cn = w->Normal()->NormalN();

                int i;
                for(i = 0; i < 2; i++) {
                    Vector o = (i == 0) ? a : b;
                    Vector oo = (i == 0) ? a.Minus(b) : b.Minus(a);
                    Vector d = (type == HORIZONTAL) ? cu : cv;
                    if(oo.Dot(d) < 0) d = d.ScaledBy(-1);

                    Vector dp = cn.Cross(d);
                    d = d.WithMagnitude(14/SS.GW.scale);
                    Vector c = o.Minus(d);
                    LineDrawOrGetDistance(o, c);
                    d = d.WithMagnitude(3/SS.GW.scale);
                    dp = dp.WithMagnitude(2/SS.GW.scale);
                    if(dogd.drawing) {
                        glBegin(GL_QUADS);
                            ssglVertex3v((c.Plus(d)).Plus(dp));
                            ssglVertex3v((c.Minus(d)).Plus(dp));
                            ssglVertex3v((c.Minus(d)).Minus(dp));
                            ssglVertex3v((c.Plus(d)).Minus(dp));
                        glEnd();
                    } else {
                        Point2d ref = SS.GW.ProjectPoint(c);
                        dogd.dmin = min(dogd.dmin, ref.DistanceTo(dogd.mp)-6);
                    }
                }
            }
            break;

        case COMMENT: {
            if(dogd.drawing && disp.style.v) {
                ssglLineWidth(Style::Width(disp.style));
                ssglColorRGB(Style::Color(disp.style));
            }
            Vector u, v;
            if(workplane.v == Entity::FREE_IN_3D.v) {
                u = gr;
                v = gu;
            } else {
                EntityBase *norm = SK.GetEntity(workplane)->Normal();
                u = norm->NormalU();
                v = norm->NormalV();
            }
            DoLabel(disp.offset, labelPos, u, v);
            break;
        }

        default: oops();
    }
}
Beispiel #3
0
void Constraint::MenuConstrain(int id) {
    Constraint c;
    ZERO(&c);
    c.group = SS.GW.activeGroup;
    c.workplane = SS.GW.ActiveWorkplane();

    SS.GW.GroupSelection();
#define gs (SS.GW.gs)

    switch(id) {
        case GraphicsWindow::MNU_DISTANCE_DIA: {
            if(gs.points == 2 && gs.n == 2) {
                c.type = PT_PT_DISTANCE;
                c.ptA = gs.point[0];
                c.ptB = gs.point[1];
            } else if(gs.lineSegments == 1 && gs.n == 1) {
                c.type = PT_PT_DISTANCE;
                Entity *e = SK.GetEntity(gs.entity[0]);
                c.ptA = e->point[0];
                c.ptB = e->point[1];
            } else if(gs.vectors == 1 && gs.points == 2 && gs.n == 3) {
                c.type = PROJ_PT_DISTANCE;
                c.ptA = gs.point[0];
                c.ptB = gs.point[1];
                c.entityA = gs.vector[0];
            } else if(gs.workplanes == 1 && gs.points == 1 && gs.n == 2) {
                c.type = PT_PLANE_DISTANCE;
                c.ptA = gs.point[0];
                c.entityA = gs.entity[0];
            } else if(gs.lineSegments == 1 && gs.points == 1 && gs.n == 2) {
                c.type = PT_LINE_DISTANCE;
                c.ptA = gs.point[0];
                c.entityA = gs.entity[0];
            } else if(gs.faces == 1 && gs.points == 1 && gs.n == 2) {
                c.type = PT_FACE_DISTANCE;
                c.ptA = gs.point[0];
                c.entityA = gs.face[0];
            } else if(gs.circlesOrArcs == 1 && gs.n == 1) {
                c.type = DIAMETER;
                c.entityA = gs.entity[0];
            } else {
                Error(
"Bad selection for distance / diameter constraint. This "
"constraint can apply to:\n\n"
"    * two points (distance between points)\n"
"    * a line segment (length)\n"
"    * two points and a line segment or normal (projected distance)\n"
"    * a workplane and a point (minimum distance)\n"
"    * a line segment and a point (minimum distance)\n"
"    * a plane face and a point (minimum distance)\n"
"    * a circle or an arc (diameter)\n");
                return;
            }
            if(c.type == PT_PT_DISTANCE || c.type == PROJ_PT_DISTANCE) {
                Vector n = SS.GW.projRight.Cross(SS.GW.projUp);
                Vector a = SK.GetEntity(c.ptA)->PointGetNum();
                Vector b = SK.GetEntity(c.ptB)->PointGetNum();
                c.disp.offset = n.Cross(a.Minus(b));
                c.disp.offset = (c.disp.offset).WithMagnitude(50/SS.GW.scale);
            } else {
                c.disp.offset = Vector::From(0, 0, 0);
            }

            c.valA = 0;
            c.ModifyToSatisfy();
            AddConstraint(&c);
            break;
        }

        case GraphicsWindow::MNU_ON_ENTITY:
            if(gs.points == 2 && gs.n == 2) {
                c.type = POINTS_COINCIDENT;
                c.ptA = gs.point[0];
                c.ptB = gs.point[1];
            } else if(gs.points == 1 && gs.workplanes == 1 && gs.n == 2) {
                c.type = PT_IN_PLANE;
                c.ptA = gs.point[0];
                c.entityA = gs.entity[0];
            } else if(gs.points == 1 && gs.lineSegments == 1 && gs.n == 2) {
                c.type = PT_ON_LINE;
                c.ptA = gs.point[0];
                c.entityA = gs.entity[0];
            } else if(gs.points == 1 && gs.circlesOrArcs == 1 && gs.n == 2) {
                c.type = PT_ON_CIRCLE;
                c.ptA = gs.point[0];
                c.entityA = gs.entity[0];
            } else if(gs.points == 1 && gs.faces == 1 && gs.n == 2) {
                c.type = PT_ON_FACE;
                c.ptA = gs.point[0];
                c.entityA = gs.face[0];
            } else {
                Error("Bad selection for on point / curve / plane constraint. "
                      "This constraint can apply to:\n\n"
                      "    * two points (points coincident)\n"
                      "    * a point and a workplane (point in plane)\n"
                      "    * a point and a line segment (point on line)\n"
                      "    * a point and a circle or arc (point on curve)\n"
                      "    * a point and a plane face (point on face)\n");
                return;
            }
            AddConstraint(&c);
            break;

        case GraphicsWindow::MNU_EQUAL:
            if(gs.lineSegments == 2 && gs.n == 2) {
                c.type = EQUAL_LENGTH_LINES;
                c.entityA = gs.entity[0];
                c.entityB = gs.entity[1];
            } else if(gs.lineSegments == 2 && gs.points == 2 && gs.n == 4) {
                c.type = EQ_PT_LN_DISTANCES;
                c.entityA = gs.entity[0];
                c.ptA = gs.point[0];
                c.entityB = gs.entity[1];
                c.ptB = gs.point[1];
            } else if(gs.lineSegments == 1 && gs.points == 2 && gs.n == 3) {
                // The same line segment for the distances, but different
                // points.
                c.type = EQ_PT_LN_DISTANCES;
                c.entityA = gs.entity[0];
                c.ptA = gs.point[0];
                c.entityB = gs.entity[0];
                c.ptB = gs.point[1];
            } else if(gs.lineSegments == 2 && gs.points == 1 && gs.n == 3) {
                c.type = EQ_LEN_PT_LINE_D;
                c.entityA = gs.entity[0];
                c.entityB = gs.entity[1];
                c.ptA = gs.point[0];
            } else if(gs.vectors == 4 && gs.n == 4) {
                c.type = EQUAL_ANGLE;
                c.entityA = gs.vector[0];
                c.entityB = gs.vector[1];
                c.entityC = gs.vector[2];
                c.entityD = gs.vector[3];
            } else if(gs.vectors == 3 && gs.n == 3) {
                c.type = EQUAL_ANGLE;
                c.entityA = gs.vector[0];
                c.entityB = gs.vector[1];
                c.entityC = gs.vector[1];
                c.entityD = gs.vector[2];
            } else if(gs.circlesOrArcs == 2 && gs.n == 2) {
                c.type = EQUAL_RADIUS;
                c.entityA = gs.entity[0];
                c.entityB = gs.entity[1];
            } else if(gs.arcs == 1 && gs.lineSegments == 1 && gs.n == 2) {
                c.type = EQUAL_LINE_ARC_LEN;
                if(SK.GetEntity(gs.entity[0])->type == Entity::ARC_OF_CIRCLE) {
                    c.entityA = gs.entity[1];
                    c.entityB = gs.entity[0];
                } else {
                    c.entityA = gs.entity[0];
                    c.entityB = gs.entity[1];
                }
            } else {
                Error("Bad selection for equal length / radius constraint. "
                      "This constraint can apply to:\n\n"
                      "    * two line segments (equal length)\n"
                      "    * two line segments and two points "
                              "(equal point-line distances)\n"
                      "    * a line segment and two points "
                              "(equal point-line distances)\n"
                      "    * a line segment, and a point and line segment "
                              "(point-line distance equals length)\n"
                      "    * four line segments or normals "
                              "(equal angle between A,B and C,D)\n"
                      "    * three line segments or normals "
                              "(equal angle between A,B and B,C)\n"
                      "    * two circles or arcs (equal radius)\n"
                      "    * a line segment and an arc "
                              "(line segment length equals arc length)\n");
                return;
            }
            if(c.type == EQUAL_ANGLE) {
                // Infer the nearest supplementary angle from the sketch.
                Vector a1 = SK.GetEntity(c.entityA)->VectorGetNum(),
                       b1 = SK.GetEntity(c.entityB)->VectorGetNum(),
                       a2 = SK.GetEntity(c.entityC)->VectorGetNum(),
                       b2 = SK.GetEntity(c.entityD)->VectorGetNum();
                double d1 = a1.Dot(b1), d2 = a2.Dot(b2);

                if(d1*d2 < 0) {
                    c.other = true;
                }
            }
            AddConstraint(&c);
            break;

        case GraphicsWindow::MNU_RATIO:
            if(gs.lineSegments == 2 && gs.n == 2) {
                c.type = LENGTH_RATIO;
                c.entityA = gs.entity[0];
                c.entityB = gs.entity[1];
            } else {
                Error("Bad selection for length ratio constraint. This "
                      "constraint can apply to:\n\n"
                      "    * two line segments\n");
                return;
            }

            c.valA = 0;
            c.ModifyToSatisfy();
            AddConstraint(&c);
            break;

        case GraphicsWindow::MNU_AT_MIDPOINT:
            if(gs.lineSegments == 1 && gs.points == 1 && gs.n == 2) {
                c.type = AT_MIDPOINT;
                c.entityA = gs.entity[0];
                c.ptA = gs.point[0];

                // If a point is at-midpoint, then no reason to also constrain
                // it on-line; so auto-remove that.
                DeleteAllConstraintsFor(PT_ON_LINE, c.entityA, c.ptA);
            } else if(gs.lineSegments == 1 && gs.workplanes == 1 && gs.n == 2) {
                c.type = AT_MIDPOINT;
                int i = SK.GetEntity(gs.entity[0])->IsWorkplane() ? 1 : 0;
                c.entityA = gs.entity[i];
                c.entityB = gs.entity[1-i];
            } else {
                Error("Bad selection for at midpoint constraint. This "
                      "constraint can apply to:\n\n"
                      "    * a line segment and a point "
                            "(point at midpoint)\n"
                      "    * a line segment and a workplane "
                            "(line's midpoint on plane)\n");
                return;
            }
            AddConstraint(&c);
            break;

        case GraphicsWindow::MNU_SYMMETRIC:
            if(gs.points == 2 &&
                                ((gs.workplanes == 1 && gs.n == 3) ||
                                 (gs.n == 2)))
            {
                c.entityA = gs.entity[0];
                c.ptA = gs.point[0];
                c.ptB = gs.point[1];
            } else if(gs.lineSegments == 1 &&
                                ((gs.workplanes == 1 && gs.n == 2) ||
                                 (gs.n == 1)))
            {
                int i = SK.GetEntity(gs.entity[0])->IsWorkplane() ? 1 : 0;
                Entity *line = SK.GetEntity(gs.entity[i]);
                c.entityA = gs.entity[1-i];
                c.ptA = line->point[0];
                c.ptB = line->point[1];
            } else if(SS.GW.LockedInWorkplane()
                        && gs.lineSegments == 2 && gs.n == 2)
            {
                Entity *l0 = SK.GetEntity(gs.entity[0]),
                       *l1 = SK.GetEntity(gs.entity[1]);

                if((l1->group.v != SS.GW.activeGroup.v) ||
                   (l1->construction && !(l0->construction)))
                {
                    SWAP(Entity *, l0, l1);
                }
                c.ptA = l1->point[0];
                c.ptB = l1->point[1];
                c.entityA = l0->h;
                c.type = SYMMETRIC_LINE;
            } else if(SS.GW.LockedInWorkplane()
                        && gs.lineSegments == 1 && gs.points == 2 && gs.n == 3)
            {
                c.ptA = gs.point[0];
                c.ptB = gs.point[1];
                c.entityA = gs.entity[0];
                c.type = SYMMETRIC_LINE;
            } else {
                Error("Bad selection for symmetric constraint. This constraint "
                      "can apply to:\n\n"
                      "    * two points or a line segment "
                          "(symmetric about workplane's coordinate axis)\n"
                      "    * line segment, and two points or a line segment "
                          "(symmetric about line segment)\n"
                      "    * workplane, and two points or a line segment "
                          "(symmetric about workplane)\n");
                return;
            }
            if(c.type != 0) {
                // Already done, symmetry about a line segment in a workplane
            } else if(c.entityA.v == Entity::NO_ENTITY.v) {
                // Horizontal / vertical symmetry, implicit symmetry plane
                // normal to the workplane
                if(c.workplane.v == Entity::FREE_IN_3D.v) {
                    Error("Must be locked in to workplane when constraining "
                          "symmetric without an explicit symmetry plane.");
                    return;
                }
                Vector pa = SK.GetEntity(c.ptA)->PointGetNum();
                Vector pb = SK.GetEntity(c.ptB)->PointGetNum();
                Vector dp = pa.Minus(pb);
                EntityBase *norm = SK.GetEntity(c.workplane)->Normal();;
                Vector u = norm->NormalU(), v = norm->NormalV();
                if(fabs(dp.Dot(u)) > fabs(dp.Dot(v))) {
                    c.type = SYMMETRIC_HORIZ;
                } else {
                    c.type = SYMMETRIC_VERT;
                }
                if(gs.lineSegments == 1) {
                    // If this line segment is already constrained horiz or
                    // vert, then auto-remove that redundant constraint.
                    DeleteAllConstraintsFor(HORIZONTAL, (gs.entity[0]),
                        Entity::NO_ENTITY);
                    DeleteAllConstraintsFor(VERTICAL, (gs.entity[0]),
                        Entity::NO_ENTITY);

                }
            } else {
                // Symmetry with a symmetry plane specified explicitly.
                c.type = SYMMETRIC;
            }
            AddConstraint(&c);
            break;

        case GraphicsWindow::MNU_VERTICAL:
        case GraphicsWindow::MNU_HORIZONTAL: {
            hEntity ha, hb;
            if(c.workplane.v == Entity::FREE_IN_3D.v) {
                Error("Select workplane before constraining horiz/vert.");
                return;
            }
            if(gs.lineSegments == 1 && gs.n == 1) {
                c.entityA = gs.entity[0];
                Entity *e = SK.GetEntity(c.entityA);
                ha = e->point[0];
                hb = e->point[1];
            } else if(gs.points == 2 && gs.n == 2) {
                ha = c.ptA = gs.point[0];
                hb = c.ptB = gs.point[1];
            } else {
                Error("Bad selection for horizontal / vertical constraint. "
                      "This constraint can apply to:\n\n"
                      "    * two points\n"
                      "    * a line segment\n");
                return;
            }
            if(id == GraphicsWindow::MNU_HORIZONTAL) {
                c.type = HORIZONTAL;
            } else {
                c.type = VERTICAL;
            }
            AddConstraint(&c);
            break;
        }

        case GraphicsWindow::MNU_ORIENTED_SAME: {
            if(gs.anyNormals == 2 && gs.n == 2) {
                c.type = SAME_ORIENTATION;
                c.entityA = gs.anyNormal[0];
                c.entityB = gs.anyNormal[1];
            } else {
                Error("Bad selection for same orientation constraint. This "
                      "constraint can apply to:\n\n"
                      "    * two normals\n");
                return;
            }
            SS.UndoRemember();

            Entity *nfree = SK.GetEntity(c.entityA);
            Entity *nref  = SK.GetEntity(c.entityB);
            if(nref->group.v == SS.GW.activeGroup.v) {
                SWAP(Entity *, nref, nfree);
            }
            if(nfree->group.v == SS.GW.activeGroup.v &&
               nref ->group.v != SS.GW.activeGroup.v)
            {
                // nfree is free, and nref is locked (since it came from a
                // previous group); so let's force nfree aligned to nref,
                // and make convergence easy
                Vector ru = nref ->NormalU(), rv = nref ->NormalV();
                Vector fu = nfree->NormalU(), fv = nfree->NormalV();

                if(fabs(fu.Dot(ru)) < fabs(fu.Dot(rv))) {
                    // There might be an odd*90 degree rotation about the
                    // normal vector; allow that, since the numerical
                    // constraint does
                    SWAP(Vector, ru, rv);
                }
                fu = fu.Dot(ru) > 0 ? ru : ru.ScaledBy(-1);
                fv = fv.Dot(rv) > 0 ? rv : rv.ScaledBy(-1);

                nfree->NormalForceTo(Quaternion::From(fu, fv));
            }
            AddConstraint(&c, false);
            break;
        }

        case GraphicsWindow::MNU_OTHER_ANGLE:
            if(gs.constraints == 1 && gs.n == 0) {
                Constraint *c = SK.GetConstraint(gs.constraint[0]);
                if(c->type == ANGLE) {
                    SS.UndoRemember();
                    c->other = !(c->other);
                    c->ModifyToSatisfy();
                    break;
                }
                if(c->type == EQUAL_ANGLE) {
                    SS.UndoRemember();
                    c->other = !(c->other);
                    SS.MarkGroupDirty(c->group);
                    SS.ScheduleGenerateAll();
                    break;
                }
            }
            Error("Must select an angle constraint.");
            return;

        case GraphicsWindow::MNU_REFERENCE:
            if(gs.constraints == 1 && gs.n == 0) {
                Constraint *c = SK.GetConstraint(gs.constraint[0]);
                if(c->HasLabel() && c->type != COMMENT) {
                    (c->reference) = !(c->reference);
                    SK.GetGroup(c->group)->clean = false;
                    SS.GenerateAll();
                    break;
                }
            }
            Error("Must select a constraint with associated label.");
            return;

        case GraphicsWindow::MNU_ANGLE: {
            if(gs.vectors == 2 && gs.n == 2) {
                c.type = ANGLE;
                c.entityA = gs.vector[0];
                c.entityB = gs.vector[1];
                c.valA = 0;
            } else {
                Error("Bad selection for angle constraint. This constraint "
                      "can apply to:\n\n"
                      "    * two line segments\n"
                      "    * a line segment and a normal\n"
                      "    * two normals\n");
                return;
            }

            Entity *ea = SK.GetEntity(c.entityA),
                   *eb = SK.GetEntity(c.entityB);
            if(ea->type == Entity::LINE_SEGMENT &&
               eb->type == Entity::LINE_SEGMENT)
            {
                Vector a0 = SK.GetEntity(ea->point[0])->PointGetNum(),
                       a1 = SK.GetEntity(ea->point[1])->PointGetNum(),
                       b0 = SK.GetEntity(eb->point[0])->PointGetNum(),
                       b1 = SK.GetEntity(eb->point[1])->PointGetNum();
                if(a0.Equals(b0) || a1.Equals(b1)) {
                    // okay, vectors should be drawn in same sense
                } else if(a0.Equals(b1) || a1.Equals(b0)) {
                    // vectors are in opposite sense
                    c.other = true;
                } else {
                    // no shared point; not clear which intersection to draw
                }
            }
            c.ModifyToSatisfy();
            AddConstraint(&c);
            break;
        }

        case GraphicsWindow::MNU_PARALLEL:
            if(gs.vectors == 2 && gs.n == 2) {
                c.type = PARALLEL;
                c.entityA = gs.vector[0];
                c.entityB = gs.vector[1];
            } else if(gs.lineSegments == 1 && gs.arcs == 1 && gs.n == 2) {
                Entity *line = SK.GetEntity(gs.entity[0]);
                Entity *arc  = SK.GetEntity(gs.entity[1]);
                if(line->type == Entity::ARC_OF_CIRCLE) {
                    SWAP(Entity *, line, arc);
                }
                Vector l0 = SK.GetEntity(line->point[0])->PointGetNum(),
                       l1 = SK.GetEntity(line->point[1])->PointGetNum();
                Vector a1 = SK.GetEntity(arc->point[1])->PointGetNum(),
                       a2 = SK.GetEntity(arc->point[2])->PointGetNum();

                if(l0.Equals(a1) || l1.Equals(a1)) {
                    c.other = false;
                } else if(l0.Equals(a2) || l1.Equals(a2)) {
                    c.other = true;
                } else {
                    Error("The tangent arc and line segment must share an "
                          "endpoint. Constrain them with Constrain -> "
                          "On Point before constraining tangent.");
                    return;
                }
                c.type = ARC_LINE_TANGENT;
                c.entityA = arc->h;
                c.entityB = line->h;
            } else if(gs.lineSegments == 1 && gs.cubics == 1 && gs.n == 2) {
                Entity *line  = SK.GetEntity(gs.entity[0]);
                Entity *cubic = SK.GetEntity(gs.entity[1]);
                if(line->type == Entity::CUBIC) {
                    SWAP(Entity *, line, cubic);
                }
                Vector l0 = SK.GetEntity(line->point[0])->PointGetNum(),
                       l1 = SK.GetEntity(line->point[1])->PointGetNum();
                Vector as = cubic->CubicGetStartNum(),
                       af = cubic->CubicGetFinishNum();

                if(l0.Equals(as) || l1.Equals(as)) {
                    c.other = false;
                } else if(l0.Equals(af) || l1.Equals(af)) {
                    c.other = true;
                } else {
                    Error("The tangent cubic and line segment must share an "
                          "endpoint. Constrain them with Constrain -> "
                          "On Point before constraining tangent.");
                    return;
                }
                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"
                      "    * two line segments, arcs, or beziers, that share "
                            "an endpoint (tangent)\n");
                return;
            }
            AddConstraint(&c);
            break;

        case GraphicsWindow::MNU_PERPENDICULAR:
            if(gs.vectors == 2 && gs.n == 2) {
                c.type = PERPENDICULAR;
                c.entityA = gs.vector[0];
                c.entityB = gs.vector[1];
            } else {
                Error("Bad selection for perpendicular constraint. This "
                      "constraint can apply to:\n\n"
                      "    * two line segments\n"
                      "    * a line segment and a normal\n"
                      "    * two normals\n");
                return;
            }
            AddConstraint(&c);
            break;

        case GraphicsWindow::MNU_WHERE_DRAGGED:
            if(gs.points == 1 && gs.n == 1) {
                c.type = WHERE_DRAGGED;
                c.ptA = gs.point[0];
            } else {
                Error("Bad selection for lock point where dragged constraint. "
                      "This constraint can apply to:\n\n"
                      "    * a point\n");
                return;
            }
            AddConstraint(&c);
            break;

        case GraphicsWindow::MNU_COMMENT:
            SS.GW.pending.operation = GraphicsWindow::MNU_COMMENT;
            SS.GW.pending.description = "click center of comment text";
            SS.ScheduleShowTW();
            break;

        default: oops();
    }

    SS.GW.ClearSelection();
    InvalidateGraphics();
}