From 67b4ba022545e01219416e788e7fc16ed589018e Mon Sep 17 00:00:00 2001
From: Chris Pavlina <pavlina.chris@gmail.com>
Date: Tue, 29 Mar 2016 20:25:15 -0400
Subject: [PATCH] eeschema: improve RemoveBacktracks() algorithm (lp:1562521)

Still isn't perfect, but removes an actual bug. It's still possible to get
weird things if you try hard, but they're not corrupt and don't trip
assertions. Consider a temporary fix.
---
 eeschema/bus-wire-junction.cpp | 45 +++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 17 deletions(-)

diff --git a/eeschema/bus-wire-junction.cpp b/eeschema/bus-wire-junction.cpp
index 6de5e9960f..1c929de721 100644
--- a/eeschema/bus-wire-junction.cpp
+++ b/eeschema/bus-wire-junction.cpp
@@ -66,34 +66,45 @@ static DLIST< SCH_ITEM > s_wires;       // when creating a new set of wires,
  */
 static void RemoveBacktracks( DLIST<SCH_ITEM>& aWires )
 {
-    SCH_LINE* last_line = NULL;
-
     EDA_ITEM* first = aWires.GetFirst();
+    std::vector<SCH_LINE*> last_lines;
+
     for( EDA_ITEM* p = first; p; )
     {
-        SCH_LINE *line = dynamic_cast<SCH_LINE*>( p );
-        if( !line )
-        {
-            wxFAIL_MSG( "RemoveBacktracks() requires SCH_LINE items" );
-            break;
-        }
+        SCH_LINE *line = static_cast<SCH_LINE*>( p );
         p = line->Next();
 
-        if( last_line )
+        if( !last_lines.empty() )
         {
-            wxASSERT_MSG( last_line->GetEndPoint() == line->GetStartPoint(),
-                    "RemoveBacktracks() requires contiguous lines" );
-            if( IsPointOnSegment( last_line->GetStartPoint(), line->GetStartPoint(),
-                        line->GetEndPoint() ) )
+            SCH_LINE* last_line = last_lines[last_lines.size() - 1];
+            bool contiguous = ( last_line->GetEndPoint() == line->GetStartPoint() );
+            bool backtracks = IsPointOnSegment( last_line->GetStartPoint(),
+                    last_line->GetEndPoint(), line->GetEndPoint() );
+            bool total_backtrack = ( last_line->GetStartPoint() == line->GetEndPoint() );
+
+            if( contiguous && backtracks )
             {
-                last_line->SetEndPoint( line->GetEndPoint() );
-                delete s_wires.Remove( line );
+                if( total_backtrack )
+                {
+                    delete s_wires.Remove( last_line );
+                    delete s_wires.Remove( line );
+                    last_lines.pop_back();
+                }
+                else
+                {
+                    last_line->SetEndPoint( line->GetEndPoint() );
+                    delete s_wires.Remove( line );
+                }
             }
             else
-                last_line = line;
+            {
+                last_lines.push_back( line );
+            }
         }
         else
-            last_line = line;
+        {
+            last_lines.push_back( line );
+        }
     }
 }