Allow edits to self-intersecting polygons.

1) Intermediate states might be self-intersecting, and we shouldn't
be policing our users on what order to do things in
2) The polygon might already be self-intersecting, at which point we're
preventing the user from fixing it.

Also includes better const management for SHAPE_POLY_SET API.

Fixes: lp:1833831
* https://bugs.launchpad.net/kicad/+bug/1833831

(cherry picked from commit a3c74051c2)

common/geometry/shape_poly_set.cpp

@@ -396,12 +396,12 @@ bool SHAPE_POLY_SET::GetNeighbourIndexes( int aGlobalIndex, int* aPrevious, int*
 }
 
 
-bool SHAPE_POLY_SET::IsPolygonSelfIntersecting( int aPolygonIndex )
+bool SHAPE_POLY_SET::IsPolygonSelfIntersecting( int aPolygonIndex ) const
 {
-    SEGMENT_ITERATOR iterator = IterateSegmentsWithHoles( aPolygonIndex );
+    CONST_SEGMENT_ITERATOR iterator = CIterateSegmentsWithHoles( aPolygonIndex );
-    SEGMENT_ITERATOR innerIterator;
+    CONST_SEGMENT_ITERATOR innerIterator;
 
-    for( iterator = IterateSegmentsWithHoles( aPolygonIndex ); iterator; iterator++ )
+    for( iterator = CIterateSegmentsWithHoles( aPolygonIndex ); iterator; iterator++ )
     {
         SEG firstSegment = *iterator;
 
@@ -423,7 +423,7 @@ bool SHAPE_POLY_SET::IsPolygonSelfIntersecting( int aPolygonIndex )
 }
 
 
-bool SHAPE_POLY_SET::IsSelfIntersecting()
+bool SHAPE_POLY_SET::IsSelfIntersecting() const
 {
     for( unsigned int polygon = 0; polygon < m_polys.size(); polygon++ )
     {

include/geometry/shape_poly_set.h

@@ -538,14 +538,14 @@ class SHAPE_POLY_SET : public SHAPE
          * @return bool - true if the aPolygonIndex-th polygon is self intersecting, false
          *              otherwise.
          */
-        bool IsPolygonSelfIntersecting( int aPolygonIndex );
+        bool IsPolygonSelfIntersecting( int aPolygonIndex ) const;
 
         /**
          * Function IsSelfIntersecting
          * Checks whether any of the polygons in the set is self intersecting.
          * @return bool - true if any of the polygons is self intersecting, false otherwise.
          */
-        bool IsSelfIntersecting();
+        bool IsSelfIntersecting() const;
 
         ///> Returns the number of triangulated polygons
         unsigned int TriangulatedPolyCount() const { return m_triangulatedPolys.size(); }
@@ -762,12 +762,35 @@ class SHAPE_POLY_SET : public SHAPE
             return iter;
         }
 
+        ///> Returns an iterator object, for iterating between aFirst and aLast outline, with or
+        /// without holes (default: without)
+        CONST_SEGMENT_ITERATOR CIterateSegments( int aFirst, int aLast,
+                                                 bool aIterateHoles = false ) const
+        {
+            CONST_SEGMENT_ITERATOR iter;
+
+            iter.m_poly = const_cast<SHAPE_POLY_SET*>( this );
+            iter.m_currentPolygon = aFirst;
+            iter.m_lastPolygon = aLast < 0 ? OutlineCount() - 1 : aLast;
+            iter.m_currentContour = 0;
+            iter.m_currentSegment = 0;
+            iter.m_iterateHoles = aIterateHoles;
+
+            return iter;
+        }
+
         ///> Returns an iterator object, for iterating aPolygonIdx-th polygon edges
         SEGMENT_ITERATOR IterateSegments( int aPolygonIdx )
         {
             return IterateSegments( aPolygonIdx, aPolygonIdx );
         }
 
+        ///> Returns an iterator object, for iterating aPolygonIdx-th polygon edges
+        CONST_SEGMENT_ITERATOR CIterateSegments( int aPolygonIdx ) const
+        {
+            return CIterateSegments( aPolygonIdx, aPolygonIdx );
+        }
+
         ///> Returns an iterator object, for all outlines in the set (no holes)
         SEGMENT_ITERATOR IterateSegments()
         {
@@ -786,6 +809,12 @@ class SHAPE_POLY_SET : public SHAPE
             return IterateSegments( aOutline, aOutline, true );
         }
 
+        ///> Returns an iterator object, for the aOutline-th outline in the set (with holes)
+        CONST_SEGMENT_ITERATOR CIterateSegmentsWithHoles( int aOutline ) const
+        {
+            return CIterateSegments( aOutline, aOutline, true );
+        }
+
         /** operations on polygons use a aFastMode param
          * if aFastMode is PM_FAST (true) the result can be a weak polygon
          * if aFastMode is PM_STRICTLY_SIMPLE (false) (default) the result is (theorically) a strictly

pcbnew/plot_brditems_plotter.cpp

@@ -780,7 +780,7 @@ void BRDITEMS_PLOTTER::PlotDrawSegment( DRAWSEGMENT* aSeg )
         {
             if( !aSeg->IsPolygonFilled() )
             {
-                for( auto it = aSeg->GetPolyShape().IterateSegments( 0 ); it; it++ )
+                for( auto it = aSeg->GetPolyShape().CIterateSegments( 0 ); it; it++ )
                 {
                     auto seg = it.Get();
                     m_plotter->ThickSegment( wxPoint( seg.A ), wxPoint( seg.B ),

pcbnew/tools/point_editor.cpp

@@ -642,26 +642,26 @@ void POINT_EDITOR::finishItem()
 }
 
 
-bool POINT_EDITOR::validatePolygon( SHAPE_POLY_SET& aModified, const SHAPE_POLY_SET* aOriginal ) const
+bool POINT_EDITOR::validatePolygon( SHAPE_POLY_SET& aPoly ) const
 {
-    if( !aModified.IsSelfIntersecting() )
+    bool valid = !aPoly.IsSelfIntersecting();
-    {
-        m_statusPopup->Hide();
-        return true;
-    }
 
     if( m_statusPopup )
+    {
+        if( valid )
+        {
+            m_statusPopup->Hide();
+        }
+        else
         {
             wxPoint p = wxGetMousePosition() + wxPoint( 20, 20 );
             m_statusPopup->Move( p );
             m_statusPopup->Popup( getEditFrame<PCB_BASE_FRAME>() );
             m_statusPopup->Expire( 1500 );
         }
+    }
 
-    if( aOriginal )
+    return valid;
-        aModified = *aOriginal;
-
-    return false;
 }
 
 
@@ -1115,14 +1115,13 @@ int POINT_EDITOR::removeCorner( const TOOL_EVENT& aEvent )
     {
         const auto& vertexIdx = vertex.second;
         auto& outline = polygon->Polygon( vertexIdx.m_polygon )[vertexIdx.m_contour];
-        bool valid = true;
 
         if( outline.PointCount() > 3 )
         {
             // the usual case: remove just the corner when there are >3 vertices
             commit.Modify( item );
             polygon->RemoveVertex( vertexIdx );
-            valid = validatePolygon( *polygon );
+            validatePolygon( *polygon );
         }
         else
         {
@@ -1143,10 +1142,7 @@ int POINT_EDITOR::removeCorner( const TOOL_EVENT& aEvent )
         setEditedPoint( nullptr );
         updatePoints();
 
-        if( valid )
         commit.Push( _( "Remove a zone/polygon corner" ) );
-        else
-            commit.Revert();
 
         // Refresh zone hatching
         if( item->Type() == PCB_ZONE_AREA_T)

pcbnew/tools/point_editor.h

@@ -92,12 +92,11 @@ private:
     void finishItem();
 
     /**
-     * Validates a polygon and restores it to its original version if available.
+     * Validates a polygon and displays a popup warning if invalid.
      * @param aModified is the polygon to be checked.
-     * @param aOriginal is the original copy that will be used to restore its state.
      * @return True if polygon is valid.
      */
-    bool validatePolygon( SHAPE_POLY_SET& aModified, const SHAPE_POLY_SET* aOriginal = nullptr ) const;
+    bool validatePolygon( SHAPE_POLY_SET& aModified ) const;
 
     ///> Updates edit points with item's points.
     void updatePoints();

pcbnew/tools/zone_create_helper.cpp

@@ -207,7 +207,7 @@ void ZONE_CREATE_HELPER::commitZone( std::unique_ptr<ZONE_CONTAINER> aZone )
             {
                 auto outline = aZone->Outline();
 
-                for( auto seg = outline->IterateSegments( 0 ); seg; seg++ )
+                for( auto seg = outline->CIterateSegments( 0 ); seg; seg++ )
                 {
                     auto new_seg = m_tool.m_editModules ?
                             new EDGE_MODULE( (MODULE *) parent ) :