From 3c6b98a0d5e2f9080c16a518fd60db83dbc7240e Mon Sep 17 00:00:00 2001
From: Jon Evans <jon@craftyjon.com>
Date: Sun, 6 Jun 2021 20:18:09 -0400
Subject: [PATCH] PNS: preserve auto-detected track width when changing via
 sizes

Fixes https://gitlab.com/kicad/code/kicad/-/issues/8046
---
 pcbnew/router/pns_kicad_iface.cpp  |  1 +
 pcbnew/router/pns_line_placer.cpp  | 12 ++++++++++--
 pcbnew/router/pns_sizes_settings.h |  5 +++++
 pcbnew/router/router_tool.cpp      |  2 +-
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/pcbnew/router/pns_kicad_iface.cpp b/pcbnew/router/pns_kicad_iface.cpp
index bf8fba98b8..5dac8b4a55 100644
--- a/pcbnew/router/pns_kicad_iface.cpp
+++ b/pcbnew/router/pns_kicad_iface.cpp
@@ -463,6 +463,7 @@ bool PNS_KICAD_IFACE_BASE::ImportSizes( PNS::SIZES_SETTINGS& aSizes, PNS::ITEM*
     }
 
     aSizes.SetTrackWidth( trackWidth );
+    aSizes.SetTrackWidthIsExplicit( !found );
 
     int viaDiameter = bds.m_ViasMinSize;
     int viaDrill = bds.m_MinThroughDrill;
diff --git a/pcbnew/router/pns_line_placer.cpp b/pcbnew/router/pns_line_placer.cpp
index de55256f4a..6836d3ec9e 100644
--- a/pcbnew/router/pns_line_placer.cpp
+++ b/pcbnew/router/pns_line_placer.cpp
@@ -1543,8 +1543,16 @@ void LINE_PLACER::UpdateSizes( const SIZES_SETTINGS& aSizes )
 
     if( !m_idle )
     {
-        m_head.SetWidth( m_sizes.TrackWidth() );
-        m_tail.SetWidth( m_sizes.TrackWidth() );
+        // If the track width was originally determined from the rules resolver ("use netclass
+        // width") or continuing from an existing track, we don't want to change the width unless
+        // the user is moving to an explicitly-specified value.
+        // NOTE: This doesn't quite correctly handle the case of moving *from* an explicit value
+        // *to* the "use netclass width" value, but that is more complicated to handle.
+        if( m_sizes.TrackWidthIsExplicit() )
+        {
+            m_head.SetWidth( m_sizes.TrackWidth() );
+            m_tail.SetWidth( m_sizes.TrackWidth() );
+        }
 
         if( m_head.EndsWithVia() )
         {
diff --git a/pcbnew/router/pns_sizes_settings.h b/pcbnew/router/pns_sizes_settings.h
index d9f34e3403..0ec6ad609f 100644
--- a/pcbnew/router/pns_sizes_settings.h
+++ b/pcbnew/router/pns_sizes_settings.h
@@ -40,6 +40,7 @@ public:
     SIZES_SETTINGS() :
             m_minClearance( 0 ),
             m_trackWidth( 155000 ),
+            m_trackWidthIsExplicit( true ),
             m_viaType( VIATYPE::THROUGH ),
             m_viaDiameter( 600000 ),
             m_viaDrill( 250000 ),
@@ -61,6 +62,9 @@ public:
     int TrackWidth() const { return m_trackWidth; }
     void SetTrackWidth( int aWidth ) { m_trackWidth = aWidth; }
 
+    bool TrackWidthIsExplicit() const { return m_trackWidthIsExplicit; }
+    void SetTrackWidthIsExplicit( bool aIsExplicit ) { m_trackWidthIsExplicit = aIsExplicit; }
+
     int DiffPairWidth() const { return m_diffPairWidth; }
     int DiffPairGap() const { return m_diffPairGap; }
 
@@ -102,6 +106,7 @@ public:
 private:
     int     m_minClearance;
     int     m_trackWidth;
+    bool    m_trackWidthIsExplicit;
 
     VIATYPE m_viaType;
     int     m_viaDiameter;
diff --git a/pcbnew/router/router_tool.cpp b/pcbnew/router/router_tool.cpp
index be6675a6e8..f7df35be36 100644
--- a/pcbnew/router/router_tool.cpp
+++ b/pcbnew/router/router_tool.cpp
@@ -1873,7 +1873,7 @@ int ROUTER_TOOL::onTrackViaSizeChanged( const TOOL_EVENT& aEvent )
     PNS::SIZES_SETTINGS sizes( m_router->Sizes() );
 
     if( !m_router->GetCurrentNets().empty() )
-        m_iface->ImportSizes( sizes, nullptr, m_router->GetCurrentNets()[0] );
+        m_iface->ImportSizes( sizes, m_startItem, m_router->GetCurrentNets()[0] );
 
     m_router->UpdateSizes( sizes );