pcbnew: Allow closed polygons as board edges

Like circles, polygons are self-closed elements that define an outline.
This allows them to be used as such for board outlines and cutouts.

Fixes: lp:1795563
* https://bugs.launchpad.net/kicad/+bug/1795563

pcbnew/board_items_to_polygon_shape_transform.cpp

@@ -578,6 +578,21 @@ void DRAWSEGMENT::TransformShapeWithClearanceToPolygon( SHAPE_POLY_SET& aCornerB
                 poly[ii] += offset;
             }
 
+            // On the edge cuts layer, a polygon should be treated as a closed set of lines
+            if( m_Layer == Edge_Cuts )
+            {
+                auto start = poly[0];
+                for( size_t ii = 1; ii < poly.size(); ii++ )
+                {
+                    TransformOvalClearanceToPolygon( aCornerBuffer, poly[ii - 1], poly[ii],
+                            linewidth, aCircleToSegmentsCount, aCorrectionFactor );
+                }
+
+                TransformOvalClearanceToPolygon( aCornerBuffer, poly[poly.size() - 1], start,
+                        linewidth, aCircleToSegmentsCount, aCorrectionFactor );
+                break;
+            }
+
             // Generate polygons for the outline + clearance
             // This code is compatible with a polygon with holes linked to external outline
             // by overlapping segments.

pcbnew/convert_drawsegment_list_to_polygon.cpp

@@ -282,6 +282,21 @@ bool ConvertOutlineToPolygon( std::vector<DRAWSEGMENT*>& aSegList, SHAPE_POLY_SE
             }
             break;
 
+        case S_POLYGON:
+            {
+                const auto poly = graphic->GetPolyShape();
+
+                for( auto iter = poly.CIterate(); iter; iter++ )
+                {
+                    if( iter->x < xmin.x )
+                    {
+                        xmin.x = iter->x;
+                        xmin.y = iter->y;
+                        xmini = i;
+                    }
+                }
+            }
+            break;
         default:
             break;
         }
@@ -302,6 +317,10 @@ bool ConvertOutlineToPolygon( std::vector<DRAWSEGMENT*>& aSegList, SHAPE_POLY_SE
         int steps = GetArcToSegmentCount( graphic->GetRadius(), ARC_LOW_DEF, 360.0 );
         TransformCircleToPolygon( aPolygons, graphic->GetCenter(), graphic->GetRadius(), steps );
     }
+    else if( graphic->GetShape() == S_POLYGON )
+    {
+        aPolygons = graphic->GetPolyShape();
+    }
     else
     {
         // Polygon start point. Arbitrarily chosen end of the
@@ -465,7 +484,16 @@ bool ConvertOutlineToPolygon( std::vector<DRAWSEGMENT*>& aSegList, SHAPE_POLY_SE
         graphic = (DRAWSEGMENT*) segList[0];
         segList.erase( segList.begin() );
 
-        if( graphic->GetShape() == S_CIRCLE )
+        // Both circles and polygons on the edge cuts layer are closed items that
+        // do not connect to other elements, so we process them independently
+        if( graphic->GetShape() == S_POLYGON )
+        {
+            for( auto it = graphic->GetPolyShape().CIterate(); it; it++ )
+            {
+                aPolygons.Append( *it, -1, hole );
+            }
+        }
+        else if( graphic->GetShape() == S_CIRCLE )
         {
             // make a circle by segments;
             wxPoint  center  = graphic->GetCenter();

pcbnew/pcb_painter.cpp

@@ -995,7 +995,12 @@ void PCB_PAINTER::draw( const DRAWSEGMENT* aSegment, int aLayer )
         }
 
         m_gal->SetLineWidth( thickness );
-        m_gal->SetIsFill( true );
+
+        if( aLayer != Edge_Cuts )
+            m_gal->SetIsFill( true );
+        else
+            m_gal->SetIsFill( false );
+
         m_gal->SetIsStroke( true );
         m_gal->DrawPolygon( shape );
 

pcbnew/plot_brditems_plotter.cpp

@@ -762,14 +762,26 @@ void BRDITEMS_PLOTTER::PlotDrawSegment( DRAWSEGMENT* aSeg )
 
     case S_POLYGON:
         {
-            m_plotter->SetCurrentLineWidth( thickness, &gbr_metadata );
-            // Draw the polygon: only one polygon is expected
-            // However we provide a multi polygon shape drawing
-            // ( for the future or to show a non expected shape )
-            for( int jj = 0; jj < aSeg->GetPolyShape().OutlineCount(); ++jj )
+            if( m_layerMask[ Edge_Cuts ] )
+            {
+                for( auto it = aSeg->GetPolyShape().IterateSegments( 0 ); it; it++ )
+                {
+                    auto seg = it.Get();
+                    m_plotter->ThickSegment( wxPoint( seg.A ), wxPoint( seg.B ),
+                            thickness, GetPlotMode(), &gbr_metadata );
+                }
+            }
+            else
             {
-                SHAPE_LINE_CHAIN& poly = aSeg->GetPolyShape().Outline( jj );
-                m_plotter->PlotPoly( poly, FILLED_SHAPE, thickness, &gbr_metadata );
+                m_plotter->SetCurrentLineWidth( thickness, &gbr_metadata );
+                // Draw the polygon: only one polygon is expected
+                // However we provide a multi polygon shape drawing
+                // ( for the future or to show a non expected shape )
+                for( int jj = 0; jj < aSeg->GetPolyShape().OutlineCount(); ++jj )
+                {
+                    SHAPE_LINE_CHAIN& poly = aSeg->GetPolyShape().Outline( jj );
+                    m_plotter->PlotPoly( poly, FILLED_SHAPE, thickness, &gbr_metadata );
+                }
             }
         }
         break;