From e221b11e3bc269e2a10ad2fca9b7fd88d87e1167 Mon Sep 17 00:00:00 2001
From: Tomasz Wlostowski <tomasz.wlostowski@cern.ch>
Date: Fri, 12 Feb 2021 00:05:46 +0100
Subject: [PATCH] GRID_HELPER: fixed arithmetic issue in segment snap distance
 check disguised as 'excessive optimization' by the dragger in the router

---
 pcbnew/router/pns_mouse_trail_tracer.cpp | 13 +++++++++++++
 pcbnew/router/pns_mouse_trail_tracer.h   |  1 +
 pcbnew/tools/pcb_grid_helper.cpp         |  4 +++-
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/pcbnew/router/pns_mouse_trail_tracer.cpp b/pcbnew/router/pns_mouse_trail_tracer.cpp
index e88d808962..6f9940a6c0 100644
--- a/pcbnew/router/pns_mouse_trail_tracer.cpp
+++ b/pcbnew/router/pns_mouse_trail_tracer.cpp
@@ -257,5 +257,18 @@ void MOUSE_TRAIL_TRACER::FlipPosture()
     m_manuallyForced = true;
 }
 
+
+VECTOR2I MOUSE_TRAIL_TRACER::GetTrailLeadVector() const
+{
+    if( m_trail.PointCount() < 2 )
+    {
+        return VECTOR2I(0, 0);
+    }
+    else
+    {
+        return m_trail.CPoint( -1 ) - m_trail.CPoint( 0 );
+    }
+}
+
 }
 
diff --git a/pcbnew/router/pns_mouse_trail_tracer.h b/pcbnew/router/pns_mouse_trail_tracer.h
index a2cb59a581..41a542fcd3 100644
--- a/pcbnew/router/pns_mouse_trail_tracer.h
+++ b/pcbnew/router/pns_mouse_trail_tracer.h
@@ -59,6 +59,7 @@ public:
 
     bool IsManuallyForced() const { return m_manuallyForced; }
 
+    VECTOR2I GetTrailLeadVector() const;
 private:
      SHAPE_LINE_CHAIN m_trail;
     int              m_tolerance;
diff --git a/pcbnew/tools/pcb_grid_helper.cpp b/pcbnew/tools/pcb_grid_helper.cpp
index 42c8122109..f6370fae69 100644
--- a/pcbnew/tools/pcb_grid_helper.cpp
+++ b/pcbnew/tools/pcb_grid_helper.cpp
@@ -79,6 +79,8 @@ VECTOR2I PCB_GRID_HELPER::AlignToSegment( const VECTOR2I& aPoint, const SEG& aSe
 {
     OPT_VECTOR2I pts[6];
 
+    const int c_gridSnapEpsilon = 2;
+
     if( !m_enableSnap )
         return aPoint;
 
@@ -97,7 +99,7 @@ VECTOR2I PCB_GRID_HELPER::AlignToSegment( const VECTOR2I& aPoint, const SEG& aSe
 
     for( int i = 0; i < 4; i++ )
     {
-        if( pts[i] && aSeg.Contains( *pts[i] ) )
+        if( pts[i] && aSeg.Distance( *pts[i] ) <= c_gridSnapEpsilon )
         {
             int d = (*pts[i] - aPoint).EuclideanNorm();