From afa201cf5008ab7fc91c60248b87cf09444a9701 Mon Sep 17 00:00:00 2001
From: Dongxu Li <dli@tamaggo.com>
Date: Tue, 17 Mar 2015 11:43:39 -0400
Subject: [PATCH] ellipse inscribed: using intersections to form quadrilateral

---
 librecad/src/lib/engine/rs_ellipse.cpp        | 71 +++++------------
 .../src/lib/information/rs_information.cpp    | 76 +++++++++++++++++++
 librecad/src/lib/information/rs_information.h |  1 +
 3 files changed, 94 insertions(+), 54 deletions(-)

diff --git a/librecad/src/lib/engine/rs_ellipse.cpp b/librecad/src/lib/engine/rs_ellipse.cpp
index 7b2bc4763d..a413ec6600 100644
--- a/librecad/src/lib/engine/rs_ellipse.cpp
+++ b/librecad/src/lib/engine/rs_ellipse.cpp
@@ -730,62 +730,25 @@ bool RS_Ellipse::createFromQuadratic(const QVector<double>& dn){
 bool	RS_Ellipse::createInscribeQuadrilateral(const std::vector<RS_Line*>& lines)
 {
 	if(lines.size() != 4) return false; //only do 4 lines
-	RS_EntityContainer container(NULL, false);
-    QVector<RS_Line*> quad;
-	for(RS_Line* p: lines){//copy the line pointers
-		if(p->getLength()<RS_TOLERANCE) return false;
-		quad.push_back(p);
-		container.addEntity(p);
-    }
-    //    std::cout<<"0\n";
-	for(size_t i=0;i<lines.size()*2;i++){//move parallel lines to opposite
-		size_t j=(i+1)%lines.size();
-
-        //        std::cout<<"("<<i<<","<<j<<")\n";
-        //        std::cout<<*quad[i]<<std::endl;
-        //        std::cout<<*quad[j]<<std::endl;
-        RS_VectorSolutions sol=RS_Information::getIntersectionLineLine(quad[i%lines.size()],quad[j]);
-        if(sol.getNumber()==0) {
-            std::swap( quad[j],quad[ (i+2)%lines.size()]); //move to oppose
-			++i;
-        }
-    }
-    //    std::cout<<"========1========\n";
+	RS_EntityContainer container(NULL, true);
+	QVector<RS_Line*> quad;
+	{ //form quadrilateral from intersections
+		RS_EntityContainer c0(NULL, false);
+		for(RS_Line*const p: lines){//copy the line pointers
+			c0.addEntity(p);
+		}
+		RS_VectorSolutions s0=RS_Information::createQuadrilateral(c0);
+		if(s0.size()!=4) return false;
+		for(size_t i=0; i<4; ++i){
+			RS_Line*const pl=new RS_Line(&container, RS_LineData(s0[i], s0[(i+1)%4]));
+			quad.push_back(pl);
+			container.addEntity(pl);
+		}
+	}
 
     QVector<RS_Line> ip;
-	for(int i=1;i<4;++i){//find intersections
-        //(0,i)
-        //        std::cout<<"(0,"<<i<<")\n";
-        RS_VectorSolutions sol0=RS_Information::getIntersectionLineLine(quad[0],quad[i]);
-        if(sol0.getNumber()==0) continue;
-        int l(1);
-		if( l==i) ++l;
-        int m(l+1);
-		if( m==i) ++m;
-        // lines in two pairs: (0, i) and (l,m)
-        //        std::cout<<"(0,"<<i<<"):("<<l<<","<<m<<")\n";
-        RS_VectorSolutions sol1=RS_Information::getIntersectionLineLine(quad[l],quad[m]);
-        if(sol1.getNumber()==0) continue;
-
-		ip.push_back(RS_Line(sol0.get(0),sol1.get(0)));
-
-    }
-
-    //    std::cout<<"20 ip.size()="<<ip.size()<<"\n";
-    if(ip.size()<2) return false; //not enough connecting lines, so, no quadrilateral defined
-    //    std::cout<<"22\n";
-    if(ip.size() == 3) {//find intersecting pair
-        //    RS_VectorSolutions sol0=RS_Information::getIntersection(line0,line1,true);
-		RS_VectorSolutions sol1=RS_Information::getIntersection(&ip[2],&ip[1],true);
-        if(sol1.getNumber()) {
-            ip[0]=ip[2];
-        }else{
-            sol1=RS_Information::getIntersection(& ip[2],&ip[0],true);
-            if(sol1.getNumber()) {
-                ip[1]=ip[2];
-            }
-        }
-    }
+	ip.push_back(RS_Line(NULL, RS_LineData(quad[0]->getStartpoint(), quad[1]->getEndpoint())));
+	ip.push_back(RS_Line(NULL, RS_LineData(quad[1]->getStartpoint(), quad[2]->getEndpoint())));
 	RS_VectorSolutions sol=RS_Information::getIntersectionLineLine( & ip[0],& ip[1]);
     if(sol.getNumber()==0) {//this should not happen
 //        RS_DEBUG->print(RS_Debug::D_WARNING, "RS_Ellipse::createInscribeQuadrilateral(): can not locate projection Center");
diff --git a/librecad/src/lib/information/rs_information.cpp b/librecad/src/lib/information/rs_information.cpp
index cd3ec7fabe..20fb075c81 100644
--- a/librecad/src/lib/information/rs_information.cpp
+++ b/librecad/src/lib/information/rs_information.cpp
@@ -25,6 +25,8 @@
 **
 **********************************************************************/
 
+#include <vector>
+#include <utility>
 #include "rs_information.h"
 
 #include "rs_arc.h"
@@ -921,3 +923,77 @@ bool RS_Information::isPointInsideContour(const RS_Vector& point,
     return ((counter%2)==1);
 }
 
+
+RS_VectorSolutions RS_Information::createQuadrilateral(const RS_EntityContainer& container)
+{
+	RS_VectorSolutions ret;
+	if(container.count()!=4) return ret;
+	RS_EntityContainer c(container);
+	std::vector<RS_Line*> lines;
+	for (RS_Entity* e=c.firstEntity(RS2::ResolveNone);
+		 e!=NULL;
+		 e=c.nextEntity(RS2::ResolveNone)) {
+		if(e->rtti()!=RS2::EntityLine) return ret;
+		lines.push_back(static_cast<RS_Line*>(e));
+	}
+	if(lines.size()!=4) return ret;
+
+	//neigbours;
+	std::vector<RS_Vector> vertices;
+	for(unsigned i=0; i<3; ++i){
+		for(unsigned j=i+1; j<4; ++j){
+			RS_VectorSolutions&& sol=RS_Information::getIntersectionLineLine(lines[i], lines[j]);
+			if(sol.size()){
+				vertices.push_back(sol.at(0));
+			}
+		}
+	}
+
+//	std::cout<<"vertices.size()="<<vertices.size()<<std::endl;
+
+	switch (vertices.size()){
+	default:
+		return ret;
+	case 4:
+		break;
+	case 5:
+	case 6:
+		for(RS_Line* pl: lines){
+			const double a0=pl->getDirection1();
+			std::vector<std::vector<RS_Vector>::iterator> left;
+			std::vector<std::vector<RS_Vector>::iterator> right;
+			for(auto it=vertices.begin(); it != vertices.end(); ++it){
+				RS_Vector&& dir=*it - pl->getNearestPointOnEntity(*it, false);
+				if(dir.squared()<RS_TOLERANCE15) continue;
+//				std::cout<<"angle="<<remainder(dir.angle() - a0, 2.*M_PI)<<std::endl;
+				if(remainder(dir.angle() - a0, 2.*M_PI) > 0.)
+					left.push_back(it);
+				else
+					right.push_back(it);
+
+				if(left.size()==2 && right.size()==1){
+					vertices.erase(right[0]);
+					break;
+				} else if(left.size()==1 && right.size()==2){
+					vertices.erase(left[0]);
+					break;
+				}
+			}
+			if(vertices.size()==4) break;
+		}
+		break;
+	}
+
+	RS_Vector center(0., 0.);
+	for(const RS_Vector& vp: vertices)
+		center += vp;
+	center *= 0.25;
+	std::sort(vertices.begin(), vertices.end(), [&center](const RS_Vector& a, const RS_Vector&b)->bool{
+		return center.angleTo(a)<center.angleTo(b);
+	});
+	for(const RS_Vector& vp: vertices){
+		ret.push_back(vp);
+//		std::cout<<"vp="<<vp<<std::endl;
+	}
+	return ret;
+}
diff --git a/librecad/src/lib/information/rs_information.h b/librecad/src/lib/information/rs_information.h
index 44ae48ab2e..717467fd88 100644
--- a/librecad/src/lib/information/rs_information.h
+++ b/librecad/src/lib/information/rs_information.h
@@ -83,6 +83,7 @@ class RS_Information {
     
 	static RS_VectorSolutions getIntersectionEllipseLine(RS_Line* line,
             RS_Ellipse* ellipse);
+	static RS_VectorSolutions createQuadrilateral(const RS_EntityContainer& container);
 
     static bool isPointInsideContour(const RS_Vector& point,
                                      RS_EntityContainer* contour,