From a667fdce1c44980cf88a046a04805f90f95172fc Mon Sep 17 00:00:00 2001
From: Roman Telezhynskyi <kroluku@gmail.com>
Date: Tue, 6 Aug 2019 16:37:55 +0300
Subject: [PATCH] New function IsLineSegmentOnLineSegment().

Helps to find if two segments are on same line have real intersection.

--HG--
branch : develop
---
 src/libs/vgeometry/vgobject.cpp | 18 ++++++++++++++++++
 src/libs/vgeometry/vgobject.h   |  2 ++
 2 files changed, 20 insertions(+)

diff --git a/src/libs/vgeometry/vgobject.cpp b/src/libs/vgeometry/vgobject.cpp
index d7bb0cea7..78d5ae5a6 100644
--- a/src/libs/vgeometry/vgobject.cpp
+++ b/src/libs/vgeometry/vgobject.cpp
@@ -472,6 +472,24 @@ bool VGObject::IsPointOnLineSegment(const QPointF &t, const QPointF &p1, const Q
     return IsPointOnLineviaPDP(t, p1, p2, accuracy);
 }
 
+//---------------------------------------------------------------------------------------------------------------------
+bool VGObject::IsLineSegmentOnLineSegment(const QLineF &seg1, const QLineF &seg2, qreal accuracy)
+{
+    const bool onLine = IsPointOnLineviaPDP(seg1.p1(), seg2.p1(), seg2.p2(), accuracy) &&
+            IsPointOnLineviaPDP(seg1.p2(), seg2.p1(), seg2.p2(), accuracy);
+    if (onLine)
+    {
+        return IsPointOnLineSegment(seg1.p1(), seg2.p1(), seg2.p2(), accuracy) ||
+                IsPointOnLineSegment(seg1.p2(), seg2.p1(), seg2.p2(), accuracy) ||
+                IsPointOnLineSegment(seg2.p1(), seg1.p1(), seg1.p2(), accuracy) ||
+                IsPointOnLineSegment(seg2.p2(), seg1.p1(), seg1.p2(), accuracy);
+    }
+    else
+    {
+        return onLine;
+    }
+}
+
 //---------------------------------------------------------------------------------------------------------------------
 QPointF VGObject::CorrectDistortion(const QPointF &t, const QPointF &p1, const QPointF &p2)
 {
diff --git a/src/libs/vgeometry/vgobject.h b/src/libs/vgeometry/vgobject.h
index be1790b7b..553788460 100644
--- a/src/libs/vgeometry/vgobject.h
+++ b/src/libs/vgeometry/vgobject.h
@@ -98,6 +98,8 @@ public:
     static void    LineCoefficients(const QLineF &line, qreal *a, qreal *b, qreal *c);
     static bool    IsPointOnLineSegment (const QPointF &t, const QPointF &p1, const QPointF &p2,
                                          qreal accuracy = accuracyPointOnLine);
+    static bool    IsLineSegmentOnLineSegment (const QLineF &seg1, const QLineF &seg2,
+                                               qreal accuracy = accuracyPointOnLine);
     static QPointF CorrectDistortion(const QPointF &t, const QPointF &p1, const QPointF &p2);
     static bool    IsPointOnLineviaPDP(const QPointF &t, const QPointF &p1, const QPointF &p2, 
                                        qreal accuracy = accuracyPointOnLine);