From 6c617d84ca43abe5918e971f595b479af5aebb15 Mon Sep 17 00:00:00 2001
From: Seth Hillbrand <seth@kipro-pcb.com>
Date: Mon, 1 Aug 2022 08:56:11 -0700
Subject: [PATCH] Prevent drag index from exceeding full line count

Simplification removes segments, so we might lose our valid index.
Ideally, we would simplify during the assembly or pass the input index
to the simplify routine to maintain the proper value.

Fixes https://gitlab.com/kicad/code/kicad/issues/12137
---
 pcbnew/router/pns_node.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pcbnew/router/pns_node.cpp b/pcbnew/router/pns_node.cpp
index 691a3d4d90..154376af90 100644
--- a/pcbnew/router/pns_node.cpp
+++ b/pcbnew/router/pns_node.cpp
@@ -1051,6 +1051,10 @@ const LINE NODE::AssembleLine( LINKED_ITEM* aSeg, int* aOriginSegmentIndex,
     // Remove duplicate verts, but do NOT remove colinear segments here!
     pl.Line().Simplify( false );
 
+    // TODO: maintain actual segment index under simplifcation system
+    if( aOriginSegmentIndex && *aOriginSegmentIndex >= pl.SegmentCount() )
+        *aOriginSegmentIndex = pl.SegmentCount() - 1;
+
     assert( pl.SegmentCount() != 0 );
 
     return pl;