From f9cfd3135143825436fdca4ff7027152bec9934f Mon Sep 17 00:00:00 2001
From: Jeff Young <jeff@rokeby.ie>
Date: Sun, 4 Oct 2020 10:46:18 +0100
Subject: [PATCH] 0 is always a collision (whether clearance is 0 or not).

---
 libs/kimath/src/geometry/shape_arc.cpp        |  2 +-
 libs/kimath/src/geometry/shape_collisions.cpp | 11 +++++------
 libs/kimath/src/geometry/shape_compound.cpp   |  2 +-
 libs/kimath/src/geometry/shape_rect.cpp       |  2 +-
 4 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/libs/kimath/src/geometry/shape_arc.cpp b/libs/kimath/src/geometry/shape_arc.cpp
index 92bb62453a..9922d7a5dc 100644
--- a/libs/kimath/src/geometry/shape_arc.cpp
+++ b/libs/kimath/src/geometry/shape_arc.cpp
@@ -202,7 +202,7 @@ bool SHAPE_ARC::Collide( const VECTOR2I& aP, int aClearance, int* aActual,
     ecoord dist_sq = ( aP - GetCenter() ).SquaredEuclideanNorm();
     ecoord dist_to_edge_sq = abs( dist_sq - r_sq );
 
-    if( dist_to_edge_sq < min_dist_sq )
+    if( dist_to_edge_sq == 0 || dist_to_edge_sq < min_dist_sq )
     {
         if( aLocation )
             *aLocation = ( aP + GetCenter() ) / 2;
diff --git a/libs/kimath/src/geometry/shape_collisions.cpp b/libs/kimath/src/geometry/shape_collisions.cpp
index 75107a749b..68e0dcf47b 100644
--- a/libs/kimath/src/geometry/shape_collisions.cpp
+++ b/libs/kimath/src/geometry/shape_collisions.cpp
@@ -49,7 +49,7 @@ static inline bool Collide( const SHAPE_CIRCLE& aA, const SHAPE_CIRCLE& aB, int
     const VECTOR2I delta = aB.GetCenter() - aA.GetCenter();
     ecoord dist_sq = delta.SquaredEuclideanNorm();
 
-    if( dist_sq < min_dist_sq )
+    if( dist_sq == 0 || dist_sq < min_dist_sq )
     {
         if( aActual )
             *aActual = std::max( 0, (int) sqrt( dist_sq ) - aA.GetRadius() - aB.GetRadius() );
@@ -114,7 +114,7 @@ static inline bool Collide( const SHAPE_RECT& aA, const SHAPE_CIRCLE& aB, int aC
         }
     }
 
-    if( inside || nearest_side_dist_sq < min_dist_sq )
+    if( inside || nearest_side_dist_sq == 0 || nearest_side_dist_sq < min_dist_sq )
     {
         if( aLocation )
             *aLocation = nearest;
@@ -192,7 +192,7 @@ static inline bool Collide( const SHAPE_CIRCLE& aA, const SHAPE_LINE_CHAIN_BASE&
         }
     }
 
-    if( closest_dist < aClearance )
+    if( closest_dist == 0 || closest_dist < aClearance )
     {
         if( aLocation )
             *aLocation = nearest;
@@ -241,7 +241,6 @@ static inline bool Collide( const SHAPE_LINE_CHAIN_BASE& aA, const SHAPE_LINE_CH
                             int aClearance, int* aActual, VECTOR2I* aLocation, VECTOR2I* aMTV )
 {
     // TODO: why doesn't this handle MTV?
-    // TODO: worse, why this doesn't handle closed shapes?
 
     int closest_dist = INT_MAX;
     VECTOR2I nearest;
@@ -272,7 +271,7 @@ static inline bool Collide( const SHAPE_LINE_CHAIN_BASE& aA, const SHAPE_LINE_CH
         nearest = aA.GetPoint( 0 );
     }
 
-    if( closest_dist < aClearance )
+    if( closest_dist == 0 || closest_dist < aClearance )
     {
         if( aLocation )
             *aLocation = nearest;
@@ -326,7 +325,7 @@ static inline bool Collide( const SHAPE_RECT& aA, const SHAPE_LINE_CHAIN_BASE& a
         }
     }
 
-    if( closest_dist < aClearance )
+    if( closest_dist == 0 || closest_dist < aClearance )
     {
         if( aLocation )
             *aLocation = nearest;
diff --git a/libs/kimath/src/geometry/shape_compound.cpp b/libs/kimath/src/geometry/shape_compound.cpp
index dad7483d5e..57a626c1ad 100644
--- a/libs/kimath/src/geometry/shape_compound.cpp
+++ b/libs/kimath/src/geometry/shape_compound.cpp
@@ -139,7 +139,7 @@ bool SHAPE_COMPOUND::Collide( const SEG& aSeg, int aClearance, int* aActual,
         }
     }
 
-    if( closest_dist < aClearance )
+    if( closest_dist == 0 || closest_dist < aClearance )
     {
         if( aLocation )
             *aLocation = nearest;
diff --git a/libs/kimath/src/geometry/shape_rect.cpp b/libs/kimath/src/geometry/shape_rect.cpp
index e4d07ccb8d..ce8cc52d9a 100644
--- a/libs/kimath/src/geometry/shape_rect.cpp
+++ b/libs/kimath/src/geometry/shape_rect.cpp
@@ -77,7 +77,7 @@ bool SHAPE_RECT::Collide( const SEG& aSeg, int aClearance, int* aActual,
         }
     }
 
-    if( closest_dist_sq < SEG::Square( aClearance ) )
+    if( closest_dist_sq == 0 || closest_dist_sq < SEG::Square( aClearance ) )
     {
         if( aLocation )
             *aLocation = nearest;