From 87d2df9d7bb80bd323e68edd1c2d9142f78b2e62 Mon Sep 17 00:00:00 2001
From: Jochen Becher <jochen_becher@gmx.de>
Date: Thu, 14 Nov 2019 21:37:23 +0100
Subject: [PATCH] modeleditor: Improve intersection of line with polygon

Change-Id: Ie546801fadedffaef24c53ce83ce0a039e77a04a
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
---
 .../qmt/infrastructure/geometryutilities.cpp  | 30 ++++++++++++++-----
 .../qmt/infrastructure/geometryutilities.h    |  3 +-
 2 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/src/libs/modelinglib/qmt/infrastructure/geometryutilities.cpp b/src/libs/modelinglib/qmt/infrastructure/geometryutilities.cpp
index 5a42bf1f33d..6f9b34aa0c2 100644
--- a/src/libs/modelinglib/qmt/infrastructure/geometryutilities.cpp
+++ b/src/libs/modelinglib/qmt/infrastructure/geometryutilities.cpp
@@ -54,22 +54,38 @@ QLineF GeometryUtilities::stretch(const QLineF &line, double p1Extension, double
 }
 
 bool GeometryUtilities::intersect(const QPolygonF &polygon, const QLineF &line,
-                                  QPointF *intersectionPoint, QLineF *intersectionLine)
+                                  QPointF *intersectionPoint, QLineF *intersectionLine,
+                                  int nearestPoint)
 {
+    bool found = false;
+    qreal mindist = 0;
+    QPointF ipoint;
+    QLineF iline;
     for (int i = 0; i <= polygon.size() - 2; ++i) {
         QLineF polygonLine(polygon.at(i), polygon.at(i+1));
+        QPointF point;
 #if QT_VERSION < QT_VERSION_CHECK(5, 14, 0)
-        QLineF::IntersectType intersectionType = polygonLine.intersect(line, intersectionPoint);
+        QLineF::IntersectType intersectionType = polygonLine.intersect(line, &point);
 #else
-        QLineF::IntersectType intersectionType = polygonLine.intersects(line, intersectionPoint);
+        QLineF::IntersectType intersectionType = polygonLine.intersects(line, &point);
 #endif
         if (intersectionType == QLineF::BoundedIntersection) {
-            if (intersectionLine)
-                *intersectionLine = polygonLine;
-            return true;
+            qreal dist = QLineF(point, nearestPoint <= 0 ? line.p1() : line.p2()).length();
+            if (!found || dist < mindist) {
+                mindist = dist;
+                ipoint = point;
+                iline = polygonLine;
+                found = true;
+            }
         }
     }
-    return false;
+    if (found) {
+        if (intersectionPoint)
+            *intersectionPoint = ipoint;
+        if (intersectionLine)
+            *intersectionLine = iline;
+    }
+    return found;
 }
 
 namespace {
diff --git a/src/libs/modelinglib/qmt/infrastructure/geometryutilities.h b/src/libs/modelinglib/qmt/infrastructure/geometryutilities.h
index f0b4f697b0b..2ec1701aa09 100644
--- a/src/libs/modelinglib/qmt/infrastructure/geometryutilities.h
+++ b/src/libs/modelinglib/qmt/infrastructure/geometryutilities.h
@@ -52,7 +52,8 @@ public:
 
     static QLineF stretch(const QLineF &line, double p1Extension, double p2Extension);
     static bool intersect(const QPolygonF &polygon, const QLineF &line,
-                          QPointF *intersectionPoint, QLineF *intersectionLine = nullptr);
+                          QPointF *intersectionPoint = nullptr, QLineF *intersectionLine = nullptr,
+                          int nearestPoint = 1);
     static bool placeRectAtLine(const QRectF &rect, const QLineF &line, double lineOffset,
                                 double distance, const QLineF &intersectionLine, QPointF *placement,
                                 Side *horizontalAlignedSide);