From 0ff6cb49d634e517517d15c9613803516103cac8 Mon Sep 17 00:00:00 2001
From: Alex <dudesuchamazing@gmail.com>
Date: Fri, 27 Jan 2023 11:06:33 +0300
Subject: [PATCH] router: When dragging tracks, don't snap to parts of the
 original line.

Fixes https://gitlab.com/kicad/code/kicad/issues/10113
---
 pcbnew/router/pns_component_dragger.h |  5 +++++
 pcbnew/router/pns_drag_algo.h         |  5 ++++-
 pcbnew/router/pns_dragger.cpp         | 10 ++++++++--
 pcbnew/router/pns_dragger.h           | 14 +++++++++++++-
 pcbnew/router/pns_router.cpp          |  2 +-
 pcbnew/router/pns_tool_base.cpp       | 19 ++++++++++++-------
 6 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/pcbnew/router/pns_component_dragger.h b/pcbnew/router/pns_component_dragger.h
index 08e63bc29b..938aa89832 100644
--- a/pcbnew/router/pns_component_dragger.h
+++ b/pcbnew/router/pns_component_dragger.h
@@ -104,6 +104,11 @@ public:
      */
     const ITEM_SET Traces() override;
 
+    virtual PNS::DRAG_MODE Mode() const override
+    {
+        return PNS::DM_COMPONENT;
+    }
+
 private:
     struct DRAGGED_CONNECTION
     {
diff --git a/pcbnew/router/pns_drag_algo.h b/pcbnew/router/pns_drag_algo.h
index 199daf601c..5c7226244f 100644
--- a/pcbnew/router/pns_drag_algo.h
+++ b/pcbnew/router/pns_drag_algo.h
@@ -25,6 +25,7 @@
 #include <memory>
 #include <math/vector2d.h>
 
+#include "pns_router.h"
 #include "pns_algo_base.h"
 #include "pns_itemset.h"
 #include "pns_layerset.h"
@@ -115,7 +116,9 @@ public:
      */
     virtual const ITEM_SET Traces() = 0;
 
-    virtual void SetMode( int aDragMode ) {};
+    virtual void SetMode( PNS::DRAG_MODE aDragMode ){};
+
+    virtual PNS::DRAG_MODE Mode() const = 0;
 
 protected:
     NODE*   m_world;
diff --git a/pcbnew/router/pns_dragger.cpp b/pcbnew/router/pns_dragger.cpp
index 97eb3577ea..0c3500f960 100644
--- a/pcbnew/router/pns_dragger.cpp
+++ b/pcbnew/router/pns_dragger.cpp
@@ -258,9 +258,15 @@ bool DRAGGER::Start( const VECTOR2I& aP, ITEM_SET& aPrimitives )
 }
 
 
-void DRAGGER::SetMode( int aMode )
+void DRAGGER::SetMode( PNS::DRAG_MODE aMode )
 {
-    m_mode = aMode;
+    m_mode = static_cast<int>( aMode );
+}
+
+
+PNS::DRAG_MODE DRAGGER::Mode() const
+{
+    return static_cast<PNS::DRAG_MODE>( m_mode );
 }
 
 
diff --git a/pcbnew/router/pns_dragger.h b/pcbnew/router/pns_dragger.h
index 2144dff9a1..3fcb515b6d 100644
--- a/pcbnew/router/pns_dragger.h
+++ b/pcbnew/router/pns_dragger.h
@@ -100,6 +100,16 @@ public:
         return m_draggedLine.Layer();
     }
 
+    const LINE& GetOriginalLine()
+{
+        return m_draggedLine;
+    }
+
+    const LINE& GetLastDragSolution()
+    {
+        return m_lastDragSolution;
+    }
+
     /**
      * Function Traces()
      *
@@ -107,7 +117,9 @@ public:
      */
     const ITEM_SET Traces() override;
 
-    void SetMode( int aDragMode ) override;
+    void SetMode( PNS::DRAG_MODE aDragMode ) override;
+
+    PNS::DRAG_MODE DRAGGER::Mode() const override;
 
 private:
     const ITEM_SET findViaFanoutByHandle ( NODE *aNode, const VIA_HANDLE& handle );
diff --git a/pcbnew/router/pns_router.cpp b/pcbnew/router/pns_router.cpp
index bf62227e1b..d2023da43c 100644
--- a/pcbnew/router/pns_router.cpp
+++ b/pcbnew/router/pns_router.cpp
@@ -185,7 +185,7 @@ bool ROUTER::StartDragging( const VECTOR2I& aP, ITEM_SET aStartItems, int aDragM
         m_state = DRAG_SEGMENT;
     }
 
-    m_dragger->SetMode( aDragMode );
+    m_dragger->SetMode( static_cast<PNS::DRAG_MODE>( aDragMode ) );
     m_dragger->SetWorld( m_world.get() );
     m_dragger->SetLogger( m_logger );
     m_dragger->SetDebugDecorator( m_iface->GetDebugDecorator() );
diff --git a/pcbnew/router/pns_tool_base.cpp b/pcbnew/router/pns_tool_base.cpp
index bdf0c79583..2884cf7505 100644
--- a/pcbnew/router/pns_tool_base.cpp
+++ b/pcbnew/router/pns_tool_base.cpp
@@ -33,6 +33,7 @@ using namespace std::placeholders;
 #include "pns_tool_base.h"
 #include "pns_arc.h"
 #include "pns_solid.h"
+#include "pns_dragger.h"
 
 
 using namespace KIGFX;
@@ -264,14 +265,18 @@ bool TOOL_BASE::checkSnap( ITEM *aItem )
     // Sync PNS engine settings with the general PCB editor options.
     auto& pnss = m_router->Settings();
 
-    // If we're dragging a track segment, don't try to snap to items on the same copper layer with same nets. This is not a perfect heuristic, but seems to work reasonably well :-)
-    // This way we avoid 'flickery' behaviour for short segments when the snap algo is trying to
-    // snap to the corners of the segments next to the one being dragged.
+    // If we're dragging a track segment, don't try to snap to items that are part of the original line.
     if( m_startItem && aItem && m_router->GetState() == ROUTER::DRAG_SEGMENT
-        && aItem->Layer() == m_startItem->Layer() && aItem->OfKind( ITEM::SEGMENT_T )
-        && m_startItem->OfKind( ITEM::SEGMENT_T ) 
-        && aItem->Net() == m_startItem->Net() )
-        return false;
+        && m_router->GetDragger() )
+    {
+        DRAGGER*     dragger = dynamic_cast<DRAGGER*>( m_router->GetDragger() );
+        LINKED_ITEM* liItem = dynamic_cast<LINKED_ITEM*>( aItem );
+
+        if( dragger && liItem && dragger->GetOriginalLine().ContainsLink( liItem ) )
+        {
+            return false;
+        }
+    }
 
     pnss.SetSnapToPads(
             frame()->GetMagneticItemsSettings()->pads == MAGNETIC_OPTIONS::CAPTURE_CURSOR_IN_TRACK_TOOL ||