/**
* Creates a tangent between a given point and a circle or arc.
* Out of the 2 possible tangents, the one closest to
* the given coordinate is returned.
*
* @param coord Coordinate to define which tangent we want (typically a
* mouse coordinate).
* @param point Point.
* @param circle Circle, arc or ellipse entity.
*/
RS_Line* RS_Creation::createTangent1(const RS_Vector& coord,
const RS_Vector& point,
RS_Entity* circle) {
RS_Line* ret = NULL;
RS_Vector circleCenter;
// check given entities:
if (circle==NULL || !point.valid ||
(circle->rtti()!=RS2::EntityArc && circle->rtti()!=RS2::EntityCircle
&& circle->rtti()!=RS2::EntityEllipse)) {
return NULL;
}
if (circle->rtti()==RS2::EntityCircle) {
circleCenter = ((RS_Circle*)circle)->getCenter();
} else if (circle->rtti()==RS2::EntityArc) {
circleCenter = ((RS_Arc*)circle)->getCenter();
} else if (circle->rtti()==RS2::EntityEllipse) {
circleCenter = ((RS_Ellipse*)circle)->getCenter();
}
// the two tangent points:
RS_VectorSolutions sol;
// calculate tangent points for arcs / circles:
if (circle->rtti()!=RS2::EntityEllipse) {
// create temp. thales circle:
RS_Vector tCenter = (point + circleCenter)/2.0;
double tRadius = point.distanceTo(tCenter);
RS_Circle tmp(NULL, RS_CircleData(tCenter, tRadius));
// get the two intersection points which are the tangent points:
sol = RS_Information::getIntersection(&tmp, circle, false);
}
// calculate tangent points for ellipses:
else {
RS_Ellipse* el = (RS_Ellipse*)circle;
//sol.alloc(2);
//sol.set(0, circleCenter);
//sol.set(1, circleCenter);
double a = el->getMajorRadius(); // the length of the major axis / 2
double b = el->getMinorRadius(); // the length of the minor axis / 2
// rotate and move point:
RS_Vector point2 = point;
point2.move(-el->getCenter());
point2.rotate(-el->getAngle());
double xp = point2.x; // coordinates of the given point
double yp = point2.y;
double xt1; // Tangent point 1
double yt1;
double xt2; // Tangent point 2
double yt2;
double a2 = a * a;
double b2 = b * b;
double d = a2 / b2 * yp / xp;
double e = a2 / xp;
double af = b2 * d * d + a2;
double bf = -b2 * d * e * 2.0;
double cf = b2 * e * e - a2 * b2;
double t = sqrt(bf * bf - af * cf * 4.0);
yt1 = (t - bf) / (af * 2.0);
xt1 = e - d * yt1;
yt2 = (-t - bf) / (af * 2.0);
xt2 = e - d * yt2;
RS_Vector s1 = RS_Vector(xt1, yt1);
RS_Vector s2 = RS_Vector(xt2, yt2);
s1.rotate(el->getAngle());
s1.move(el->getCenter());
s2.rotate(el->getAngle());
s2.move(el->getCenter());
sol.push_back(s1);
sol.push_back(s2);
}
if (sol.getNumber() < 2 ) {
return NULL;
}
if (!sol.get(0).valid || !sol.get(1).valid) {
return NULL;
}
// create all possible tangents:
RS_Line* poss[2];
RS_LineData d;
d = RS_LineData(sol.get(0), point);
poss[0] = new RS_Line(NULL, d);
d = RS_LineData(sol.get(1), point);
poss[1] = new RS_Line(NULL, d);
// find closest tangent:
double minDist = RS_MAXDOUBLE;
double dist;
int idx = -1;
for (int i=0; i<2; ++i) {
dist = poss[i]->getDistanceToPoint(coord);
if (dist<minDist) {
minDist = dist;
idx = i;
}
}
// create the closest tangent:
if (idx!=-1) {
RS_LineData d = poss[idx]->getData();
for (int i=0; i<2; ++i) {
delete poss[i];
}
if (document!=NULL && handleUndo) {
document->startUndoCycle();
}
ret = new RS_Line(container, d);
ret->setLayerToActive();
ret->setPenToActive();
if (container!=NULL) {
container->addEntity(ret);
}
if (document!=NULL && handleUndo) {
document->addUndoable(ret);
document->endUndoCycle();
}
if (graphicView!=NULL) {
graphicView->drawEntity(ret);
}
} else {
ret = NULL;
}
return ret;
}
