From 58c006bc45b5a750aabc9beaf92776c1598d2e53 Mon Sep 17 00:00:00 2001
From: Jeff Young <jeff@rokeby.ie>
Date: Fri, 23 Oct 2020 13:42:48 +0100
Subject: [PATCH] Register properties for ARC elements so we can get their
 netclass.

Also improves GAL arc drawing and polygonization.

Fixes https://gitlab.com/kicad/code/kicad/issues/6039
---
 common/gal/opengl/opengl_gal.cpp       |  7 ++++++-
 libs/kimath/src/geometry/shape_arc.cpp |  3 ++-
 pcbnew/class_track.cpp                 | 17 +++++++++++++++++
 pcbnew/pcb_painter.cpp                 |  4 +++-
 4 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/common/gal/opengl/opengl_gal.cpp b/common/gal/opengl/opengl_gal.cpp
index f706ac9b38..07cb3ee0fc 100644
--- a/common/gal/opengl/opengl_gal.cpp
+++ b/common/gal/opengl/opengl_gal.cpp
@@ -841,7 +841,12 @@ void OPENGL_GAL::DrawArcSegment( const VECTOR2D& aCenterPoint, double aRadius, d
     // Swap the angles, if start angle is greater than end angle
     SWAP( aStartAngle, >, aEndAngle );
 
-    const double alphaIncrement = calcAngleStep( aRadius );
+    // Bigger arcs need smaller alpha increment to make them look smooth
+    const double alphaIncrement = std::min( 1e6 / aRadius, 2.0 * M_PI / CIRCLE_POINTS );
+
+    // Draw entirely within the real arc boundary (ie: put all polygonization error inside)
+    double correctionFactor = cos( M_PI / (double) CIRCLE_POINTS );
+    aRadius *= correctionFactor;
 
     Save();
     currentManager->Translate( aCenterPoint.x, aCenterPoint.y, 0.0 );
diff --git a/libs/kimath/src/geometry/shape_arc.cpp b/libs/kimath/src/geometry/shape_arc.cpp
index f3b7337fe1..7000fbfc1d 100644
--- a/libs/kimath/src/geometry/shape_arc.cpp
+++ b/libs/kimath/src/geometry/shape_arc.cpp
@@ -375,13 +375,14 @@ const SHAPE_LINE_CHAIN SHAPE_ARC::ConvertToPolyline( double aAccuracy ) const
 
     int n;
 
-    if( r == 0.0 )
+    if( r < aAccuracy )
     {
         n = 0;
     }
     else
     {
         n = GetArcToSegmentCount( r, aAccuracy, ca );
+        r -= aAccuracy / 2;         // Split the error on either side of arc
     }
 
     for( int i = 0; i <= n ; i++ )
diff --git a/pcbnew/class_track.cpp b/pcbnew/class_track.cpp
index 6836d71f31..673bf7d2bb 100644
--- a/pcbnew/class_track.cpp
+++ b/pcbnew/class_track.cpp
@@ -1074,6 +1074,23 @@ static struct TRACK_VIA_DESC
         propMgr.AddProperty( new PROPERTY<TRACK, int>( _HKI( "End Y" ),
             &TRACK::SetEndY, &TRACK::GetEndY, PROPERTY_DISPLAY::DISTANCE ) );
 
+        // Arc
+        REGISTER_TYPE( ARC );
+        propMgr.InheritsAfter( TYPE_HASH( ARC ), TYPE_HASH( BOARD_CONNECTED_ITEM ) );
+
+        propMgr.AddProperty( new PROPERTY<TRACK, int>( _HKI( "Width" ),
+            &ARC::SetWidth, &ARC::GetWidth, PROPERTY_DISPLAY::DISTANCE ) );
+        propMgr.ReplaceProperty( TYPE_HASH( BOARD_ITEM ), _HKI( "Position X" ),
+            new PROPERTY<ARC, int, BOARD_ITEM>( _HKI( "Origin X" ),
+            &TRACK::SetX, &ARC::GetX, PROPERTY_DISPLAY::DISTANCE ) );
+        propMgr.ReplaceProperty( TYPE_HASH( BOARD_ITEM ), _HKI( "Position Y" ),
+            new PROPERTY<ARC, int, BOARD_ITEM>( _HKI( "Origin Y" ),
+            &TRACK::SetY, &ARC::GetY, PROPERTY_DISPLAY::DISTANCE ) );
+        propMgr.AddProperty( new PROPERTY<TRACK, int>( _HKI( "End X" ),
+            &TRACK::SetEndX, &ARC::GetEndX, PROPERTY_DISPLAY::DISTANCE ) );
+        propMgr.AddProperty( new PROPERTY<TRACK, int>( _HKI( "End Y" ),
+            &TRACK::SetEndY, &ARC::GetEndY, PROPERTY_DISPLAY::DISTANCE ) );
+
         // Via
         REGISTER_TYPE( VIA );
         propMgr.InheritsAfter( TYPE_HASH( VIA ), TYPE_HASH( BOARD_CONNECTED_ITEM ) );
diff --git a/pcbnew/pcb_painter.cpp b/pcbnew/pcb_painter.cpp
index 1dc72cf8d1..b58b858d37 100644
--- a/pcbnew/pcb_painter.cpp
+++ b/pcbnew/pcb_painter.cpp
@@ -587,13 +587,15 @@ void PCB_PAINTER::draw( const ARC* aArc, int aLayer )
 
         if( ( m_pcbSettings.m_clearance & clearanceFlags ) == clearanceFlags )
         {
+            int clearance = aArc->GetOwnClearance( m_pcbSettings.GetActiveLayer() );
+
             m_gal->SetLineWidth( m_pcbSettings.m_outlineWidth );
             m_gal->SetIsFill( false );
             m_gal->SetIsStroke( true );
             m_gal->SetStrokeColor( color );
 
             m_gal->DrawArcSegment( center, radius, start_angle, start_angle + angle,
-                                   width + aArc->GetOwnClearance( ToLAYER_ID( aLayer ) ) * 2 );
+                                   width + clearance * 2 );
         }
     }
 }