Multichannel: split out some geometric routines

Putting them somewhere in the geom utils means they
can be reused, and also tested if needed.

libs/kimath/include/geometry/shape_utils.h

@@ -75,6 +75,11 @@ OPT_VECTOR2I GetSharedEndpoint( const SEG& aSegA, const SEG& aSegB );
  */
 std::array<SEG, 4> BoxToSegs( const BOX2I& aBox );
 
+/**
+ * Add the 4 corners of a BOX2I to a vector.
+ */
+void CollectBoxCorners( const BOX2I& aBox, std::vector<VECTOR2I>& aCorners );
+
 /**
  * Get the segments of a box that are in the given direction.
  *
@@ -142,4 +147,19 @@ VECTOR2I GetPoint( const SHAPE_RECT& aRect, DIRECTION_45::Directions aDir, int a
  */
 std::vector<TYPED_POINT2I> GetCircleKeyPoints( const CIRCLE& aCircle, bool aIncludeCenter );
 
+
+/*
+ * Take a polygon and 'rectify' it, so that all sides are H/V.
+ *
+ * The entire original polygon is contained within the new one.
+ * The new polygon will pass though each original corner,
+ * but it can have additional corners, or corners can be simplified away.
+ *
+ * E.g.:
+ *     ____           _______
+ *    /    \___    -> |     |___
+ *    |________\      |_________|
+ */
+SHAPE_LINE_CHAIN RectifyPolygon( const SHAPE_LINE_CHAIN& aPoly );
+
 } // namespace KIGEOM

libs/kimath/src/geometry/shape_utils.cpp

@@ -80,6 +80,15 @@ std::array<SEG, 4> KIGEOM::BoxToSegs( const BOX2I& aBox )
 }
 
 
+void KIGEOM::CollectBoxCorners( const BOX2I& aBox, std::vector<VECTOR2I>& aCorners )
+{
+    aCorners.push_back( { aBox.GetLeft(), aBox.GetTop() } );
+    aCorners.push_back( { aBox.GetRight(), aBox.GetTop() } );
+    aCorners.push_back( { aBox.GetRight(), aBox.GetBottom() } );
+    aCorners.push_back( { aBox.GetLeft(), aBox.GetBottom() } );
+}
+
+
 std::vector<SEG> KIGEOM::GetSegsInDirection( const BOX2I& aBox, DIRECTION_45::Directions aDir )
 {
     // clang-format off
@@ -332,4 +341,38 @@ std::vector<TYPED_POINT2I> KIGEOM::GetCircleKeyPoints( const CIRCLE& aCircle, bo
     }
 
     return pts;
+}
+
+
+SHAPE_LINE_CHAIN KIGEOM::RectifyPolygon( const SHAPE_LINE_CHAIN& aPoly )
+{
+    SHAPE_LINE_CHAIN raOutline;
+
+    const auto handleSegment = [&]( const SEG& aSeg )
+    {
+        const VECTOR2I p0( aSeg.A.x, aSeg.B.y );
+        const VECTOR2I p1( aSeg.B.x, aSeg.A.y );
+
+        raOutline.Append( aSeg.A );
+        if( !aPoly.PointInside( p0 ) )
+            raOutline.Append( p0 );
+        else
+            raOutline.Append( p1 );
+    };
+
+    for( int i = 0; i < aPoly.SegmentCount(); i++ )
+    {
+        handleSegment( aPoly.CSegment( i ) );
+    }
+
+    // Manually handle the last segment if not closed
+    if( !aPoly.IsClosed() )
+    {
+        handleSegment( SEG( aPoly.CPoint( -1 ), aPoly.CPoint( 0 ) ) );
+    }
+
+    raOutline.SetClosed( true );
+    raOutline.Simplify();
+
+    return raOutline;
 }

pcbnew/tools/multichannel_tool.cpp

@@ -34,6 +34,7 @@
 
 #include <zone.h>
 #include <geometry/convex_hull.h>
+#include <geometry/shape_utils.h>
 #include <pcb_group.h>
 #include <connectivity/connectivity_data.h>
 #include <connectivity/topo_match.h>
@@ -168,43 +169,22 @@ MULTICHANNEL_TOOL::queryComponentsInComponentClass( const wxString& aComponentCl
 const SHAPE_LINE_CHAIN MULTICHANNEL_TOOL::buildRAOutline( std::set<FOOTPRINT*>& aFootprints,
                                                           int                   aMargin )
 {
-    std::vector<VECTOR2I> bbCorners, hullVertices;
+    std::vector<VECTOR2I> bbCorners;
+    bbCorners.reserve( aFootprints.size() * 4 );
 
     for( auto fp : aFootprints )
     {
-        auto bb = fp->GetBoundingBox( false );
-        bb.Inflate( aMargin );
-
-        bbCorners.push_back( VECTOR2I( bb.GetX(), bb.GetY() ) );
-        bbCorners.push_back( VECTOR2I( bb.GetX() + bb.GetWidth(), bb.GetY() ) );
-        bbCorners.push_back( VECTOR2I( bb.GetX() + bb.GetWidth(), bb.GetY() + bb.GetHeight() ) );
-        bbCorners.push_back( VECTOR2I( bb.GetX(), bb.GetY() + bb.GetHeight() ) );
+        const BOX2I bb = fp->GetBoundingBox( false ).GetInflated( aMargin );
+        KIGEOM::CollectBoxCorners( bb, bbCorners );
     }
 
+    std::vector<VECTOR2I> hullVertices;
     BuildConvexHull( hullVertices, bbCorners );
 
     SHAPE_LINE_CHAIN hull( hullVertices );
-    SHAPE_LINE_CHAIN raOutline;
 
-    // make the newly computed convex hull use only 90 degree segments
-    hull.SetClosed( true );
-    for( int i = 0; i < hull.SegmentCount(); i++ )
-    {
-        const auto&    seg = hull.CSegment( i );
-        const VECTOR2I p0( seg.A.x, seg.B.y );
-        const VECTOR2I p1( seg.B.x, seg.A.y );
-
-        raOutline.Append( seg.A );
-        if( !hull.PointInside( p0 ) )
-            raOutline.Append( p0 );
-        else
-            raOutline.Append( p1 );
-    }
-
-    raOutline.SetClosed( true );
-    raOutline.Simplify();
-
-    return raOutline;
+    // Make the newly computed convex hull use only 90 degree segments
+    return KIGEOM::RectifyPolygon( hull );
 }